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* let import_iovec deal with compat_iovecs as well
@ 2020-09-18 12:45 Christoph Hellwig
  2020-09-18 12:45 ` [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag Christoph Hellwig
                   ` (9 more replies)
  0 siblings, 10 replies; 67+ messages in thread
From: Christoph Hellwig @ 2020-09-18 12:45 UTC (permalink / raw)
  To: Alexander Viro
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

Hi Al,

this series changes import_iovec to transparently deal with comat iovec
structures, and then cleanups up a lot of code dupliation.  But to get
there it first has to fix the pre-existing bug that io_uring compat
contexts don't trigger the in_compat_syscall() check.  This has so far
been relatively harmless as very little code callable from io_uring used
the check, and even that code that could be called usually wasn't.

Diffstat
 arch/arm64/include/asm/unistd32.h                  |   10 
 arch/mips/kernel/syscalls/syscall_n32.tbl          |   10 
 arch/mips/kernel/syscalls/syscall_o32.tbl          |   10 
 arch/parisc/kernel/syscalls/syscall.tbl            |   10 
 arch/powerpc/kernel/syscalls/syscall.tbl           |   10 
 arch/s390/kernel/syscalls/syscall.tbl              |   10 
 arch/sparc/include/asm/compat.h                    |    3 
 arch/sparc/kernel/syscalls/syscall.tbl             |   10 
 arch/x86/entry/syscall_x32.c                       |    5 
 arch/x86/entry/syscalls/syscall_32.tbl             |   10 
 arch/x86/entry/syscalls/syscall_64.tbl             |   10 
 arch/x86/include/asm/compat.h                      |    2 
 block/scsi_ioctl.c                                 |   12 
 drivers/scsi/sg.c                                  |    9 
 fs/aio.c                                           |   38 --
 fs/io_uring.c                                      |   21 -
 fs/read_write.c                                    |  307 ++++-----------------
 fs/splice.c                                        |   57 ---
 include/linux/compat.h                             |   29 -
 include/linux/fs.h                                 |    7 
 include/linux/sched.h                              |    1 
 include/linux/uio.h                                |    7 
 include/uapi/asm-generic/unistd.h                  |   12 
 lib/iov_iter.c                                     |   30 --
 mm/process_vm_access.c                             |   69 ----
 net/compat.c                                       |    4 
 security/keys/compat.c                             |   37 --
 security/keys/internal.h                           |    5 
 security/keys/keyctl.c                             |    2 
 tools/include/uapi/asm-generic/unistd.h            |   12 
 tools/perf/arch/powerpc/entry/syscalls/syscall.tbl |   10 
 tools/perf/arch/s390/entry/syscalls/syscall.tbl    |   10 
 tools/perf/arch/x86/entry/syscalls/syscall_64.tbl  |   10 
 33 files changed, 207 insertions(+), 582 deletions(-)

^ permalink raw reply	[flat|nested] 67+ messages in thread

* [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-18 12:45 let import_iovec deal with compat_iovecs as well Christoph Hellwig
@ 2020-09-18 12:45 ` Christoph Hellwig
  2020-09-18 13:40   ` Al Viro
  2020-09-20 15:15   ` Matthew Wilcox
  2020-09-18 12:45 ` [PATCH 2/9] compat.h: fix a spelling error in <linux/compat.h> Christoph Hellwig
                   ` (8 subsequent siblings)
  9 siblings, 2 replies; 67+ messages in thread
From: Christoph Hellwig @ 2020-09-18 12:45 UTC (permalink / raw)
  To: Alexander Viro
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

Add a flag to force processing a syscall as a compat syscall.  This is
required so that in_compat_syscall() works for I/O submitted by io_uring
helper threads on behalf of compat syscalls.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/sparc/include/asm/compat.h | 3 ++-
 arch/x86/include/asm/compat.h   | 2 +-
 fs/io_uring.c                   | 9 +++++++++
 include/linux/compat.h          | 5 ++++-
 include/linux/sched.h           | 1 +
 5 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/arch/sparc/include/asm/compat.h b/arch/sparc/include/asm/compat.h
index 40a267b3bd5208..fee6c51d36e869 100644
--- a/arch/sparc/include/asm/compat.h
+++ b/arch/sparc/include/asm/compat.h
@@ -211,7 +211,8 @@ static inline int is_compat_task(void)
 static inline bool in_compat_syscall(void)
 {
 	/* Vector 0x110 is LINUX_32BIT_SYSCALL_TRAP */
-	return pt_regs_trap_type(current_pt_regs()) == 0x110;
+	return pt_regs_trap_type(current_pt_regs()) == 0x110 ||
+		(current->flags & PF_FORCE_COMPAT);
 }
 #define in_compat_syscall in_compat_syscall
 #endif
diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h
index d4edf281fff49d..fbab072d4e5b31 100644
--- a/arch/x86/include/asm/compat.h
+++ b/arch/x86/include/asm/compat.h
@@ -208,7 +208,7 @@ static inline bool in_32bit_syscall(void)
 #ifdef CONFIG_COMPAT
 static inline bool in_compat_syscall(void)
 {
-	return in_32bit_syscall();
+	return in_32bit_syscall() || (current->flags & PF_FORCE_COMPAT);
 }
 #define in_compat_syscall in_compat_syscall	/* override the generic impl */
 #endif
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3790c7fe9fee22..5755d557c3f7bc 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5449,6 +5449,9 @@ static int io_req_defer_prep(struct io_kiocb *req,
 	if (unlikely(ret))
 		return ret;
 
+	if (req->ctx->compat)
+		current->flags |= PF_FORCE_COMPAT;
+
 	switch (req->opcode) {
 	case IORING_OP_NOP:
 		break;
@@ -5546,6 +5549,7 @@ static int io_req_defer_prep(struct io_kiocb *req,
 		break;
 	}
 
+	current->flags &= ~PF_FORCE_COMPAT;
 	return ret;
 }
 
@@ -5669,6 +5673,9 @@ static int io_issue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 	struct io_ring_ctx *ctx = req->ctx;
 	int ret;
 
+	if (ctx->compat)
+		current->flags |= PF_FORCE_COMPAT;
+
 	switch (req->opcode) {
 	case IORING_OP_NOP:
 		ret = io_nop(req, cs);
@@ -5898,6 +5905,8 @@ static int io_issue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 		break;
 	}
 
+	current->flags &= ~PF_FORCE_COMPAT;
+
 	if (ret)
 		return ret;
 
diff --git a/include/linux/compat.h b/include/linux/compat.h
index b354ce58966e2d..685066f7ad325f 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -891,7 +891,10 @@ asmlinkage long compat_sys_socketcall(int call, u32 __user *args);
  */
 
 #ifndef in_compat_syscall
-static inline bool in_compat_syscall(void) { return is_compat_task(); }
+static inline bool in_compat_syscall(void)
+{
+	return is_compat_task() || (current->flags & PF_FORCE_COMPAT);
+}
 #endif
 
 /**
diff --git a/include/linux/sched.h b/include/linux/sched.h
index afe01e232935fa..c8b183b5655a1e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1491,6 +1491,7 @@ extern struct pid *cad_pid;
  */
 #define PF_IDLE			0x00000002	/* I am an IDLE thread */
 #define PF_EXITING		0x00000004	/* Getting shut down */
+#define PF_FORCE_COMPAT		0x00000008	/* acting as compat task */
 #define PF_VCPU			0x00000010	/* I'm a virtual CPU */
 #define PF_WQ_WORKER		0x00000020	/* I'm a workqueue worker */
 #define PF_FORKNOEXEC		0x00000040	/* Forked but didn't exec */
-- 
2.28.0


^ permalink raw reply	[flat|nested] 67+ messages in thread

* [PATCH 2/9] compat.h: fix a spelling error in <linux/compat.h>
  2020-09-18 12:45 let import_iovec deal with compat_iovecs as well Christoph Hellwig
  2020-09-18 12:45 ` [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag Christoph Hellwig
@ 2020-09-18 12:45 ` Christoph Hellwig
  2020-09-18 13:37   ` Johannes Thumshirn
  2020-09-18 12:45 ` [PATCH 3/9] fs: explicitly check for CHECK_IOVEC_ONLY in rw_copy_check_uvector Christoph Hellwig
                   ` (7 subsequent siblings)
  9 siblings, 1 reply; 67+ messages in thread
From: Christoph Hellwig @ 2020-09-18 12:45 UTC (permalink / raw)
  To: Alexander Viro
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

We only have not compat_sys_readv64v2 syscall, only a
compat_sys_preadv64v2 syscall one.  This probably worked given that the
syscall was not referenced from anywhere but the x86 syscall table.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 include/linux/compat.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/compat.h b/include/linux/compat.h
index 685066f7ad325f..69968c124b3cad 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -812,7 +812,7 @@ asmlinkage ssize_t compat_sys_pwritev2(compat_ulong_t fd,
 		const struct compat_iovec __user *vec,
 		compat_ulong_t vlen, u32 pos_low, u32 pos_high, rwf_t flags);
 #ifdef __ARCH_WANT_COMPAT_SYS_PREADV64V2
-asmlinkage long  compat_sys_readv64v2(unsigned long fd,
+asmlinkage long  compat_sys_preadv64v2(unsigned long fd,
 		const struct compat_iovec __user *vec,
 		unsigned long vlen, loff_t pos, rwf_t flags);
 #endif
-- 
2.28.0


^ permalink raw reply	[flat|nested] 67+ messages in thread

* [PATCH 3/9] fs: explicitly check for CHECK_IOVEC_ONLY in rw_copy_check_uvector
  2020-09-18 12:45 let import_iovec deal with compat_iovecs as well Christoph Hellwig
  2020-09-18 12:45 ` [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag Christoph Hellwig
  2020-09-18 12:45 ` [PATCH 2/9] compat.h: fix a spelling error in <linux/compat.h> Christoph Hellwig
@ 2020-09-18 12:45 ` Christoph Hellwig
  2020-09-18 12:56   ` Matthew Wilcox
  2020-09-18 13:39   ` Johannes Thumshirn
  2020-09-18 12:45 ` [PATCH 4/9] fs: handle the compat case in import_iovec Christoph Hellwig
                   ` (6 subsequent siblings)
  9 siblings, 2 replies; 67+ messages in thread
From: Christoph Hellwig @ 2020-09-18 12:45 UTC (permalink / raw)
  To: Alexander Viro
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

Explicitly check for the magic value insted of implicitly relying on
its number representation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/read_write.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 5db58b8c78d0dd..f153116bc5399b 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -840,8 +840,7 @@ ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
 			ret = -EINVAL;
 			goto out;
 		}
-		if (type >= 0
-		    && unlikely(!access_ok(buf, len))) {
+		if (type != CHECK_IOVEC_ONLY && unlikely(!access_ok(buf, len))) {
 			ret = -EFAULT;
 			goto out;
 		}
@@ -911,7 +910,7 @@ ssize_t compat_rw_copy_check_uvector(int type,
 		}
 		if (len < 0)	/* size_t not fitting in compat_ssize_t .. */
 			goto out;
-		if (type >= 0 &&
+		if (type != CHECK_IOVEC_ONLY &&
 		    !access_ok(compat_ptr(buf), len)) {
 			ret = -EFAULT;
 			goto out;
-- 
2.28.0


^ permalink raw reply	[flat|nested] 67+ messages in thread

* [PATCH 4/9] fs: handle the compat case in import_iovec
  2020-09-18 12:45 let import_iovec deal with compat_iovecs as well Christoph Hellwig
                   ` (2 preceding siblings ...)
  2020-09-18 12:45 ` [PATCH 3/9] fs: explicitly check for CHECK_IOVEC_ONLY in rw_copy_check_uvector Christoph Hellwig
@ 2020-09-18 12:45 ` Christoph Hellwig
  2020-09-18 12:45 ` [PATCH 5/9] fs: remove various compat readv/writev helpers Christoph Hellwig
                   ` (5 subsequent siblings)
  9 siblings, 0 replies; 67+ messages in thread
From: Christoph Hellwig @ 2020-09-18 12:45 UTC (permalink / raw)
  To: Alexander Viro
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

Use in compat_syscall to import either native or the compat iovecs, and
remove the now superflous compat_import_iovec.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/scsi_ioctl.c     |  12 +---
 drivers/scsi/sg.c      |   9 +--
 fs/aio.c               |  38 +++++-------
 fs/io_uring.c          |  12 +---
 fs/read_write.c        | 127 +++++++++++++++--------------------------
 fs/splice.c            |   2 +-
 include/linux/compat.h |   6 --
 include/linux/fs.h     |   7 +--
 include/linux/uio.h    |   7 ---
 lib/iov_iter.c         |  30 +---------
 mm/process_vm_access.c |   9 +--
 net/compat.c           |   4 +-
 security/keys/compat.c |   5 +-
 13 files changed, 83 insertions(+), 185 deletions(-)

diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index ef722f04f88a93..e08df86866ee5d 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -333,16 +333,8 @@ static int sg_io(struct request_queue *q, struct gendisk *bd_disk,
 		struct iov_iter i;
 		struct iovec *iov = NULL;
 
-#ifdef CONFIG_COMPAT
-		if (in_compat_syscall())
-			ret = compat_import_iovec(rq_data_dir(rq),
-				   hdr->dxferp, hdr->iovec_count,
-				   0, &iov, &i);
-		else
-#endif
-			ret = import_iovec(rq_data_dir(rq),
-				   hdr->dxferp, hdr->iovec_count,
-				   0, &iov, &i);
+		ret = import_iovec(rq_data_dir(rq), hdr->dxferp,
+				   hdr->iovec_count, 0, &iov, &i);
 		if (ret < 0)
 			goto out_free_cdb;
 
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 20472aaaf630a4..bfa8d77322d732 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1820,14 +1820,7 @@ sg_start_req(Sg_request *srp, unsigned char *cmd)
 		struct iovec *iov = NULL;
 		struct iov_iter i;
 
-#ifdef CONFIG_COMPAT
-		if (in_compat_syscall())
-			res = compat_import_iovec(rw, hp->dxferp, iov_count,
-						  0, &iov, &i);
-		else
-#endif
-			res = import_iovec(rw, hp->dxferp, iov_count,
-					   0, &iov, &i);
+		res = import_iovec(rw, hp->dxferp, iov_count, 0, &iov, &i);
 		if (res < 0)
 			return res;
 
diff --git a/fs/aio.c b/fs/aio.c
index d5ec303855669d..b377f5c2048e18 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1478,8 +1478,7 @@ static int aio_prep_rw(struct kiocb *req, const struct iocb *iocb)
 }
 
 static ssize_t aio_setup_rw(int rw, const struct iocb *iocb,
-		struct iovec **iovec, bool vectored, bool compat,
-		struct iov_iter *iter)
+		struct iovec **iovec, bool vectored, struct iov_iter *iter)
 {
 	void __user *buf = (void __user *)(uintptr_t)iocb->aio_buf;
 	size_t len = iocb->aio_nbytes;
@@ -1489,11 +1488,6 @@ static ssize_t aio_setup_rw(int rw, const struct iocb *iocb,
 		*iovec = NULL;
 		return ret;
 	}
-#ifdef CONFIG_COMPAT
-	if (compat)
-		return compat_import_iovec(rw, buf, len, UIO_FASTIOV, iovec,
-				iter);
-#endif
 	return import_iovec(rw, buf, len, UIO_FASTIOV, iovec, iter);
 }
 
@@ -1517,8 +1511,7 @@ static inline void aio_rw_done(struct kiocb *req, ssize_t ret)
 	}
 }
 
-static int aio_read(struct kiocb *req, const struct iocb *iocb,
-			bool vectored, bool compat)
+static int aio_read(struct kiocb *req, const struct iocb *iocb, bool vectored)
 {
 	struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
 	struct iov_iter iter;
@@ -1535,7 +1528,7 @@ static int aio_read(struct kiocb *req, const struct iocb *iocb,
 	if (unlikely(!file->f_op->read_iter))
 		return -EINVAL;
 
-	ret = aio_setup_rw(READ, iocb, &iovec, vectored, compat, &iter);
+	ret = aio_setup_rw(READ, iocb, &iovec, vectored, &iter);
 	if (ret < 0)
 		return ret;
 	ret = rw_verify_area(READ, file, &req->ki_pos, iov_iter_count(&iter));
@@ -1545,8 +1538,7 @@ static int aio_read(struct kiocb *req, const struct iocb *iocb,
 	return ret;
 }
 
-static int aio_write(struct kiocb *req, const struct iocb *iocb,
-			 bool vectored, bool compat)
+static int aio_write(struct kiocb *req, const struct iocb *iocb, bool vectored)
 {
 	struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
 	struct iov_iter iter;
@@ -1563,7 +1555,7 @@ static int aio_write(struct kiocb *req, const struct iocb *iocb,
 	if (unlikely(!file->f_op->write_iter))
 		return -EINVAL;
 
-	ret = aio_setup_rw(WRITE, iocb, &iovec, vectored, compat, &iter);
+	ret = aio_setup_rw(WRITE, iocb, &iovec, vectored, &iter);
 	if (ret < 0)
 		return ret;
 	ret = rw_verify_area(WRITE, file, &req->ki_pos, iov_iter_count(&iter));
@@ -1799,8 +1791,7 @@ static int aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb)
 }
 
 static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
-			   struct iocb __user *user_iocb, struct aio_kiocb *req,
-			   bool compat)
+			   struct iocb __user *user_iocb, struct aio_kiocb *req)
 {
 	req->ki_filp = fget(iocb->aio_fildes);
 	if (unlikely(!req->ki_filp))
@@ -1833,13 +1824,13 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
 
 	switch (iocb->aio_lio_opcode) {
 	case IOCB_CMD_PREAD:
-		return aio_read(&req->rw, iocb, false, compat);
+		return aio_read(&req->rw, iocb, false);
 	case IOCB_CMD_PWRITE:
-		return aio_write(&req->rw, iocb, false, compat);
+		return aio_write(&req->rw, iocb, false);
 	case IOCB_CMD_PREADV:
-		return aio_read(&req->rw, iocb, true, compat);
+		return aio_read(&req->rw, iocb, true);
 	case IOCB_CMD_PWRITEV:
-		return aio_write(&req->rw, iocb, true, compat);
+		return aio_write(&req->rw, iocb, true);
 	case IOCB_CMD_FSYNC:
 		return aio_fsync(&req->fsync, iocb, false);
 	case IOCB_CMD_FDSYNC:
@@ -1852,8 +1843,7 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
 	}
 }
 
-static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
-			 bool compat)
+static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb)
 {
 	struct aio_kiocb *req;
 	struct iocb iocb;
@@ -1882,7 +1872,7 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
 	if (unlikely(!req))
 		return -EAGAIN;
 
-	err = __io_submit_one(ctx, &iocb, user_iocb, req, compat);
+	err = __io_submit_one(ctx, &iocb, user_iocb, req);
 
 	/* Done with the synchronous reference */
 	iocb_put(req);
@@ -1941,7 +1931,7 @@ SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
 			break;
 		}
 
-		ret = io_submit_one(ctx, user_iocb, false);
+		ret = io_submit_one(ctx, user_iocb);
 		if (ret)
 			break;
 	}
@@ -1983,7 +1973,7 @@ COMPAT_SYSCALL_DEFINE3(io_submit, compat_aio_context_t, ctx_id,
 			break;
 		}
 
-		ret = io_submit_one(ctx, compat_ptr(user_iocb), true);
+		ret = io_submit_one(ctx, compat_ptr(user_iocb));
 		if (ret)
 			break;
 	}
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 5755d557c3f7bc..dc888f911f04b4 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2837,12 +2837,6 @@ static ssize_t __io_import_iovec(int rw, struct io_kiocb *req,
 		return ret;
 	}
 
-#ifdef CONFIG_COMPAT
-	if (req->ctx->compat)
-		return compat_import_iovec(rw, buf, sqe_len, UIO_FASTIOV,
-						iovec, iter);
-#endif
-
 	return import_iovec(rw, buf, sqe_len, UIO_FASTIOV, iovec, iter);
 }
 
@@ -4220,9 +4214,9 @@ static int __io_compat_recvmsg_copy_hdr(struct io_kiocb *req,
 		sr->len = iomsg->iov[0].iov_len;
 		iomsg->iov = NULL;
 	} else {
-		ret = compat_import_iovec(READ, uiov, len, UIO_FASTIOV,
-						&iomsg->iov,
-						&iomsg->msg.msg_iter);
+		ret = import_iovec(READ, (struct iovec __user *)uiov, len,
+				   UIO_FASTIOV, &iomsg->iov,
+				   &iomsg->msg.msg_iter);
 		if (ret < 0)
 			return ret;
 	}
diff --git a/fs/read_write.c b/fs/read_write.c
index f153116bc5399b..2f961c653ce561 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -752,6 +752,38 @@ static ssize_t do_loop_readv_writev(struct file *filp, struct iov_iter *iter,
 	return ret;
 }
 
+static int compat_copy_iovecs_from_user(struct iovec *iov,
+		const struct iovec __user *uvector, unsigned long nr_segs)
+{
+	const struct compat_iovec __user *uiov =
+		(const struct compat_iovec __user *)uvector;
+	unsigned long i;
+	int ret = -EFAULT;
+
+	if (!user_access_begin(uvector, nr_segs * sizeof(*uvector)))
+		return -EFAULT;
+
+	for (i = 0; i < nr_segs; i++) {
+		compat_uptr_t buf;
+		compat_ssize_t len;
+
+		unsafe_get_user(len, &uiov[i].iov_len, out);
+		unsafe_get_user(buf, &uiov[i].iov_base, out);
+
+		/* check for compat_size_t not fitting in compat_ssize_t .. */
+		if (len < 0) {
+			ret = -EINVAL;
+			goto out;
+		}
+		iov[i].iov_base = compat_ptr(buf);
+		iov[i].iov_len = len;
+	}
+	ret = 0;
+out:
+	user_access_end();
+	return ret;
+}
+
 /**
  * rw_copy_check_uvector() - Copy an array of &struct iovec from userspace
  *     into the kernel and check that it is valid.
@@ -808,6 +840,7 @@ ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
 		ret = -EINVAL;
 		goto out;
 	}
+
 	if (nr_segs > fast_segs) {
 		iov = kmalloc_array(nr_segs, sizeof(struct iovec), GFP_KERNEL);
 		if (iov == NULL) {
@@ -815,9 +848,16 @@ ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
 			goto out;
 		}
 	}
-	if (copy_from_user(iov, uvector, nr_segs*sizeof(*uvector))) {
-		ret = -EFAULT;
-		goto out;
+
+	if (in_compat_syscall()) {
+		ret = compat_copy_iovecs_from_user(iov, uvector, nr_segs);
+		if (ret)
+			goto out;
+	} else {
+		if (copy_from_user(iov, uvector, nr_segs * sizeof(*uvector))) {
+			ret = -EFAULT;
+			goto out;
+		}
 	}
 
 	/*
@@ -855,81 +895,6 @@ ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
 	return ret;
 }
 
-#ifdef CONFIG_COMPAT
-ssize_t compat_rw_copy_check_uvector(int type,
-		const struct compat_iovec __user *uvector, unsigned long nr_segs,
-		unsigned long fast_segs, struct iovec *fast_pointer,
-		struct iovec **ret_pointer)
-{
-	compat_ssize_t tot_len;
-	struct iovec *iov = *ret_pointer = fast_pointer;
-	ssize_t ret = 0;
-	int seg;
-
-	/*
-	 * SuS says "The readv() function *may* fail if the iovcnt argument
-	 * was less than or equal to 0, or greater than {IOV_MAX}.  Linux has
-	 * traditionally returned zero for zero segments, so...
-	 */
-	if (nr_segs == 0)
-		goto out;
-
-	ret = -EINVAL;
-	if (nr_segs > UIO_MAXIOV)
-		goto out;
-	if (nr_segs > fast_segs) {
-		ret = -ENOMEM;
-		iov = kmalloc_array(nr_segs, sizeof(struct iovec), GFP_KERNEL);
-		if (iov == NULL)
-			goto out;
-	}
-	*ret_pointer = iov;
-
-	ret = -EFAULT;
-	if (!access_ok(uvector, nr_segs*sizeof(*uvector)))
-		goto out;
-
-	/*
-	 * Single unix specification:
-	 * We should -EINVAL if an element length is not >= 0 and fitting an
-	 * ssize_t.
-	 *
-	 * In Linux, the total length is limited to MAX_RW_COUNT, there is
-	 * no overflow possibility.
-	 */
-	tot_len = 0;
-	ret = -EINVAL;
-	for (seg = 0; seg < nr_segs; seg++) {
-		compat_uptr_t buf;
-		compat_ssize_t len;
-
-		if (__get_user(len, &uvector->iov_len) ||
-		   __get_user(buf, &uvector->iov_base)) {
-			ret = -EFAULT;
-			goto out;
-		}
-		if (len < 0)	/* size_t not fitting in compat_ssize_t .. */
-			goto out;
-		if (type != CHECK_IOVEC_ONLY &&
-		    !access_ok(compat_ptr(buf), len)) {
-			ret = -EFAULT;
-			goto out;
-		}
-		if (len > MAX_RW_COUNT - tot_len)
-			len = MAX_RW_COUNT - tot_len;
-		tot_len += len;
-		iov->iov_base = compat_ptr(buf);
-		iov->iov_len = (compat_size_t) len;
-		uvector++;
-		iov++;
-	}
-	ret = tot_len;
-
-out:
-	return ret;
-}
-#endif
-
 static ssize_t do_iter_read(struct file *file, struct iov_iter *iter,
 		loff_t *pos, rwf_t flags)
 {
@@ -1256,7 +1221,8 @@ static size_t compat_readv(struct file *file,
 	struct iov_iter iter;
 	ssize_t ret;
 
-	ret = compat_import_iovec(READ, vec, vlen, UIO_FASTIOV, &iov, &iter);
+	ret = import_iovec(READ, (const struct iovec __user *)vec, vlen,
+			   UIO_FASTIOV, &iov, &iter);
 	if (ret >= 0) {
 		ret = do_iter_read(file, &iter, pos, flags);
 		kfree(iov);
@@ -1364,7 +1330,8 @@ static size_t compat_writev(struct file *file,
 	struct iov_iter iter;
 	ssize_t ret;
 
-	ret = compat_import_iovec(WRITE, vec, vlen, UIO_FASTIOV, &iov, &iter);
+	ret = import_iovec(WRITE, (const struct iovec __user *)vec, vlen,
+			   UIO_FASTIOV, &iov, &iter);
 	if (ret >= 0) {
 		file_start_write(file);
 		ret = do_iter_write(file, &iter, pos, flags);
diff --git a/fs/splice.c b/fs/splice.c
index d7c8a7c4db07ff..132d42b9871f9b 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1387,7 +1387,7 @@ COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, io
 	if (error)
 		return error;
 
-	error = compat_import_iovec(type, iov32, nr_segs,
+	error = import_iovec(type, (struct iovec __user *)iov32, nr_segs,
 			     ARRAY_SIZE(iovstack), &iov, &iter);
 	if (error >= 0) {
 		error = do_vmsplice(f.file, &iter, flags);
diff --git a/include/linux/compat.h b/include/linux/compat.h
index 69968c124b3cad..ad6dc56e8828d6 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -451,12 +451,6 @@ extern long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
 
 struct epoll_event;	/* fortunately, this one is fixed-layout */
 
-extern ssize_t compat_rw_copy_check_uvector(int type,
-		const struct compat_iovec __user *uvector,
-		unsigned long nr_segs,
-		unsigned long fast_segs, struct iovec *fast_pointer,
-		struct iovec **ret_pointer);
-
 extern void __user *compat_alloc_user_space(unsigned long len);
 
 int compat_restore_altstack(const compat_stack_t __user *uss);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7519ae003a082c..3cc0ee0de45648 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -179,10 +179,9 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
 #define FMODE_BUF_RASYNC	((__force fmode_t)0x40000000)
 
 /*
- * Flag for rw_copy_check_uvector and compat_rw_copy_check_uvector
- * that indicates that they should check the contents of the iovec are
- * valid, but not check the memory that the iovec elements
- * points too.
+ * Flag for rw_copy_check_uvector  that indicates that they should check the
+ * contents of the iovec are valid, but not check the memory that the iovec
+ * elements points too.
  */
 #define CHECK_IOVEC_ONLY -1
 
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 3835a8a8e9eae0..2c14e55687fec6 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -270,13 +270,6 @@ ssize_t import_iovec(int type, const struct iovec __user * uvector,
 		 unsigned nr_segs, unsigned fast_segs,
 		 struct iovec **iov, struct iov_iter *i);
 
-#ifdef CONFIG_COMPAT
-struct compat_iovec;
-ssize_t compat_import_iovec(int type, const struct compat_iovec __user * uvector,
-		 unsigned nr_segs, unsigned fast_segs,
-		 struct iovec **iov, struct iov_iter *i);
-#endif
-
 int import_single_range(int type, void __user *buf, size_t len,
 		 struct iovec *iov, struct iov_iter *i);
 
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 5e40786c8f1232..792f31c1cd96ba 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -10,6 +10,7 @@
 #include <net/checksum.h>
 #include <linux/scatterlist.h>
 #include <linux/instrumented.h>
+#include <linux/compat.h>
 
 #define PIPE_PARANOIA /* for now */
 
@@ -1678,32 +1679,8 @@ ssize_t import_iovec(int type, const struct iovec __user * uvector,
 {
 	ssize_t n;
 	struct iovec *p;
-	n = rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
-				  *iov, &p);
-	if (n < 0) {
-		if (p != *iov)
-			kfree(p);
-		*iov = NULL;
-		return n;
-	}
-	iov_iter_init(i, type, p, nr_segs, n);
-	*iov = p == *iov ? NULL : p;
-	return n;
-}
-EXPORT_SYMBOL(import_iovec);
 
-#ifdef CONFIG_COMPAT
-#include <linux/compat.h>
-
-ssize_t compat_import_iovec(int type,
-		const struct compat_iovec __user * uvector,
-		unsigned nr_segs, unsigned fast_segs,
-		struct iovec **iov, struct iov_iter *i)
-{
-	ssize_t n;
-	struct iovec *p;
-	n = compat_rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
-				  *iov, &p);
+	n = rw_copy_check_uvector(type, uvector, nr_segs, fast_segs, *iov, &p);
 	if (n < 0) {
 		if (p != *iov)
 			kfree(p);
@@ -1714,8 +1691,7 @@ ssize_t compat_import_iovec(int type,
 	*iov = p == *iov ? NULL : p;
 	return n;
 }
-EXPORT_SYMBOL(compat_import_iovec);
-#endif
+EXPORT_SYMBOL(import_iovec);
 
 int import_single_range(int rw, void __user *buf, size_t len,
 		 struct iovec *iov, struct iov_iter *i)
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index 29c052099affdc..f21feebbd48f39 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -329,14 +329,15 @@ compat_process_vm_rw(compat_pid_t pid,
 	if (flags != 0)
 		return -EINVAL;
 
-	rc = compat_import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter);
+	rc = import_iovec(dir, (const struct iovec __user *)lvec, liovcnt,
+			  UIO_FASTIOV, &iov_l, &iter);
 	if (rc < 0)
 		return rc;
 	if (!iov_iter_count(&iter))
 		goto free_iovecs;
-	rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt,
-					  UIO_FASTIOV, iovstack_r,
-					  &iov_r);
+	rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY,
+				   (const struct iovec __user *)rvec, riovcnt,
+				   UIO_FASTIOV, iovstack_r, &iov_r);
 	if (rc <= 0)
 		goto free_iovecs;
 
diff --git a/net/compat.c b/net/compat.c
index 95ce707a30a31d..ddd15af3a2837b 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -98,8 +98,8 @@ int get_compat_msghdr(struct msghdr *kmsg,
 	if (err)
 		return err;
 
-	err = compat_import_iovec(save_addr ? READ : WRITE, compat_ptr(ptr),
-				   len, UIO_FASTIOV, iov, &kmsg->msg_iter);
+	err = import_iovec(save_addr ? READ : WRITE, compat_ptr(ptr), len,
+			   UIO_FASTIOV, iov, &kmsg->msg_iter);
 	return err < 0 ? err : 0;
 }
 
diff --git a/security/keys/compat.c b/security/keys/compat.c
index 6ee9d8f6a4a5bb..7ae531db031cf8 100644
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -33,9 +33,8 @@ static long compat_keyctl_instantiate_key_iov(
 	if (!_payload_iov)
 		ioc = 0;
 
-	ret = compat_import_iovec(WRITE, _payload_iov, ioc,
-				  ARRAY_SIZE(iovstack), &iov,
-				  &from);
+	ret = import_iovec(WRITE, (const struct iovec __user *)_payload_iov,
+			   ioc, ARRAY_SIZE(iovstack), &iov, &from);
 	if (ret < 0)
 		return ret;
 
-- 
2.28.0


^ permalink raw reply	[flat|nested] 67+ messages in thread

* [PATCH 5/9] fs: remove various compat readv/writev helpers
  2020-09-18 12:45 let import_iovec deal with compat_iovecs as well Christoph Hellwig
                   ` (3 preceding siblings ...)
  2020-09-18 12:45 ` [PATCH 4/9] fs: handle the compat case in import_iovec Christoph Hellwig
@ 2020-09-18 12:45 ` Christoph Hellwig
  2020-09-18 12:45 ` [PATCH 6/9] fs: remove the compat readv/writev syscalls Christoph Hellwig
                   ` (4 subsequent siblings)
  9 siblings, 0 replies; 67+ messages in thread
From: Christoph Hellwig @ 2020-09-18 12:45 UTC (permalink / raw)
  To: Alexander Viro
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

Now that import_iovec handles compat iovecs as well, all the duplicated
code in the compat readv/writev helpers is not needed.  Remove them
and switch the compat syscall handlers to use the native helpers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/read_write.c | 179 ++++++++----------------------------------------
 1 file changed, 30 insertions(+), 149 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 2f961c653ce561..9eb63c53da78f2 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1211,226 +1211,107 @@ SYSCALL_DEFINE6(pwritev2, unsigned long, fd, const struct iovec __user *, vec,
 	return do_pwritev(fd, vec, vlen, pos, flags);
 }
 
+/*
+ * Various compat syscalls.  Note that they all pretend to take a native
+ * iovec - import_iovec will properly treat those as compat_iovecs based on
+ * in_compat_syscall().
+ */
 #ifdef CONFIG_COMPAT
-static size_t compat_readv(struct file *file,
-			   const struct compat_iovec __user *vec,
-			   unsigned long vlen, loff_t *pos, rwf_t flags)
-{
-	struct iovec iovstack[UIO_FASTIOV];
-	struct iovec *iov = iovstack;
-	struct iov_iter iter;
-	ssize_t ret;
-
-	ret = import_iovec(READ, (const struct iovec __user *)vec, vlen,
-			   UIO_FASTIOV, &iov, &iter);
-	if (ret >= 0) {
-		ret = do_iter_read(file, &iter, pos, flags);
-		kfree(iov);
-	}
-	if (ret > 0)
-		add_rchar(current, ret);
-	inc_syscr(current);
-	return ret;
-}
-
-static size_t do_compat_readv(compat_ulong_t fd,
-				 const struct compat_iovec __user *vec,
-				 compat_ulong_t vlen, rwf_t flags)
-{
-	struct fd f = fdget_pos(fd);
-	ssize_t ret;
-	loff_t pos;
-
-	if (!f.file)
-		return -EBADF;
-	pos = f.file->f_pos;
-	ret = compat_readv(f.file, vec, vlen, &pos, flags);
-	if (ret >= 0)
-		f.file->f_pos = pos;
-	fdput_pos(f);
-	return ret;
-
-}
-
 COMPAT_SYSCALL_DEFINE3(readv, compat_ulong_t, fd,
-		const struct compat_iovec __user *,vec,
+		const struct iovec __user *, vec,
 		compat_ulong_t, vlen)
 {
-	return do_compat_readv(fd, vec, vlen, 0);
-}
-
-static long do_compat_preadv64(unsigned long fd,
-				  const struct compat_iovec __user *vec,
-				  unsigned long vlen, loff_t pos, rwf_t flags)
-{
-	struct fd f;
-	ssize_t ret;
-
-	if (pos < 0)
-		return -EINVAL;
-	f = fdget(fd);
-	if (!f.file)
-		return -EBADF;
-	ret = -ESPIPE;
-	if (f.file->f_mode & FMODE_PREAD)
-		ret = compat_readv(f.file, vec, vlen, &pos, flags);
-	fdput(f);
-	return ret;
+	return do_readv(fd, vec, vlen, 0);
 }
 
 #ifdef __ARCH_WANT_COMPAT_SYS_PREADV64
 COMPAT_SYSCALL_DEFINE4(preadv64, unsigned long, fd,
-		const struct compat_iovec __user *,vec,
+		const struct iovec __user *, vec,
 		unsigned long, vlen, loff_t, pos)
 {
-	return do_compat_preadv64(fd, vec, vlen, pos, 0);
+	return do_preadv(fd, vec, vlen, pos, 0);
 }
 #endif
 
 COMPAT_SYSCALL_DEFINE5(preadv, compat_ulong_t, fd,
-		const struct compat_iovec __user *,vec,
+		const struct iovec __user *, vec,
 		compat_ulong_t, vlen, u32, pos_low, u32, pos_high)
 {
 	loff_t pos = ((loff_t)pos_high << 32) | pos_low;
 
-	return do_compat_preadv64(fd, vec, vlen, pos, 0);
+	return do_preadv(fd, vec, vlen, pos, 0);
 }
 
 #ifdef __ARCH_WANT_COMPAT_SYS_PREADV64V2
 COMPAT_SYSCALL_DEFINE5(preadv64v2, unsigned long, fd,
-		const struct compat_iovec __user *,vec,
+		const struct iovec __user *, vec,
 		unsigned long, vlen, loff_t, pos, rwf_t, flags)
 {
 	if (pos == -1)
-		return do_compat_readv(fd, vec, vlen, flags);
-
-	return do_compat_preadv64(fd, vec, vlen, pos, flags);
+		return do_readv(fd, vec, vlen, flags);
+	return do_preadv(fd, vec, vlen, pos, flags);
 }
 #endif
 
 COMPAT_SYSCALL_DEFINE6(preadv2, compat_ulong_t, fd,
-		const struct compat_iovec __user *,vec,
+		const struct iovec __user *, vec,
 		compat_ulong_t, vlen, u32, pos_low, u32, pos_high,
 		rwf_t, flags)
 {
 	loff_t pos = ((loff_t)pos_high << 32) | pos_low;
 
 	if (pos == -1)
-		return do_compat_readv(fd, vec, vlen, flags);
-
-	return do_compat_preadv64(fd, vec, vlen, pos, flags);
-}
-
-static size_t compat_writev(struct file *file,
-			    const struct compat_iovec __user *vec,
-			    unsigned long vlen, loff_t *pos, rwf_t flags)
-{
-	struct iovec iovstack[UIO_FASTIOV];
-	struct iovec *iov = iovstack;
-	struct iov_iter iter;
-	ssize_t ret;
-
-	ret = import_iovec(WRITE, (const struct iovec __user *)vec, vlen,
-			   UIO_FASTIOV, &iov, &iter);
-	if (ret >= 0) {
-		file_start_write(file);
-		ret = do_iter_write(file, &iter, pos, flags);
-		file_end_write(file);
-		kfree(iov);
-	}
-	if (ret > 0)
-		add_wchar(current, ret);
-	inc_syscw(current);
-	return ret;
-}
-
-static size_t do_compat_writev(compat_ulong_t fd,
-				  const struct compat_iovec __user* vec,
-				  compat_ulong_t vlen, rwf_t flags)
-{
-	struct fd f = fdget_pos(fd);
-	ssize_t ret;
-	loff_t pos;
-
-	if (!f.file)
-		return -EBADF;
-	pos = f.file->f_pos;
-	ret = compat_writev(f.file, vec, vlen, &pos, flags);
-	if (ret >= 0)
-		f.file->f_pos = pos;
-	fdput_pos(f);
-	return ret;
+		return do_readv(fd, vec, vlen, flags);
+	return do_preadv(fd, vec, vlen, pos, flags);
 }
 
 COMPAT_SYSCALL_DEFINE3(writev, compat_ulong_t, fd,
-		const struct compat_iovec __user *, vec,
+		const struct iovec __user *, vec,
 		compat_ulong_t, vlen)
 {
-	return do_compat_writev(fd, vec, vlen, 0);
-}
-
-static long do_compat_pwritev64(unsigned long fd,
-				   const struct compat_iovec __user *vec,
-				   unsigned long vlen, loff_t pos, rwf_t flags)
-{
-	struct fd f;
-	ssize_t ret;
-
-	if (pos < 0)
-		return -EINVAL;
-	f = fdget(fd);
-	if (!f.file)
-		return -EBADF;
-	ret = -ESPIPE;
-	if (f.file->f_mode & FMODE_PWRITE)
-		ret = compat_writev(f.file, vec, vlen, &pos, flags);
-	fdput(f);
-	return ret;
+	return do_writev(fd, vec, vlen, 0);
 }
 
 #ifdef __ARCH_WANT_COMPAT_SYS_PWRITEV64
 COMPAT_SYSCALL_DEFINE4(pwritev64, unsigned long, fd,
-		const struct compat_iovec __user *,vec,
+		const struct iovec __user *, vec,
 		unsigned long, vlen, loff_t, pos)
 {
-	return do_compat_pwritev64(fd, vec, vlen, pos, 0);
+	return do_pwritev(fd, vec, vlen, pos, 0);
 }
 #endif
 
 COMPAT_SYSCALL_DEFINE5(pwritev, compat_ulong_t, fd,
-		const struct compat_iovec __user *,vec,
+		const struct iovec __user *,vec,
 		compat_ulong_t, vlen, u32, pos_low, u32, pos_high)
 {
 	loff_t pos = ((loff_t)pos_high << 32) | pos_low;
 
-	return do_compat_pwritev64(fd, vec, vlen, pos, 0);
+	return do_pwritev(fd, vec, vlen, pos, 0);
 }
 
 #ifdef __ARCH_WANT_COMPAT_SYS_PWRITEV64V2
 COMPAT_SYSCALL_DEFINE5(pwritev64v2, unsigned long, fd,
-		const struct compat_iovec __user *,vec,
+		const struct iovec __user *, vec,
 		unsigned long, vlen, loff_t, pos, rwf_t, flags)
 {
 	if (pos == -1)
-		return do_compat_writev(fd, vec, vlen, flags);
-
-	return do_compat_pwritev64(fd, vec, vlen, pos, flags);
+		return do_writev(fd, vec, vlen, flags);
+	return do_pwritev(fd, vec, vlen, pos, flags);
 }
 #endif
 
 COMPAT_SYSCALL_DEFINE6(pwritev2, compat_ulong_t, fd,
-		const struct compat_iovec __user *,vec,
+		const struct iovec __user *,vec,
 		compat_ulong_t, vlen, u32, pos_low, u32, pos_high, rwf_t, flags)
 {
 	loff_t pos = ((loff_t)pos_high << 32) | pos_low;
 
 	if (pos == -1)
-		return do_compat_writev(fd, vec, vlen, flags);
-
-	return do_compat_pwritev64(fd, vec, vlen, pos, flags);
+		return do_writev(fd, vec, vlen, flags);
+	return do_pwritev(fd, vec, vlen, pos, flags);
 }
-
-#endif
+#endif /* CONFIG_COMPAT */
 
 static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
 		  	   size_t count, loff_t max)
-- 
2.28.0


^ permalink raw reply	[flat|nested] 67+ messages in thread

* [PATCH 6/9] fs: remove the compat readv/writev syscalls
  2020-09-18 12:45 let import_iovec deal with compat_iovecs as well Christoph Hellwig
                   ` (4 preceding siblings ...)
  2020-09-18 12:45 ` [PATCH 5/9] fs: remove various compat readv/writev helpers Christoph Hellwig
@ 2020-09-18 12:45 ` Christoph Hellwig
  2020-09-18 12:45 ` [PATCH 7/9] fs: remove compat_sys_vmsplice Christoph Hellwig
                   ` (3 subsequent siblings)
  9 siblings, 0 replies; 67+ messages in thread
From: Christoph Hellwig @ 2020-09-18 12:45 UTC (permalink / raw)
  To: Alexander Viro
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

Now that import_iovec handles compat iovecs, the native readv and writev
syscalls can be used for the compat case as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/arm64/include/asm/unistd32.h                  |  4 ++--
 arch/mips/kernel/syscalls/syscall_n32.tbl          |  4 ++--
 arch/mips/kernel/syscalls/syscall_o32.tbl          |  4 ++--
 arch/parisc/kernel/syscalls/syscall.tbl            |  4 ++--
 arch/powerpc/kernel/syscalls/syscall.tbl           |  4 ++--
 arch/s390/kernel/syscalls/syscall.tbl              |  4 ++--
 arch/sparc/kernel/syscalls/syscall.tbl             |  4 ++--
 arch/x86/entry/syscall_x32.c                       |  2 ++
 arch/x86/entry/syscalls/syscall_32.tbl             |  4 ++--
 arch/x86/entry/syscalls/syscall_64.tbl             |  4 ++--
 fs/read_write.c                                    | 14 --------------
 include/linux/compat.h                             |  4 ----
 include/uapi/asm-generic/unistd.h                  |  4 ++--
 tools/include/uapi/asm-generic/unistd.h            |  4 ++--
 tools/perf/arch/powerpc/entry/syscalls/syscall.tbl |  4 ++--
 tools/perf/arch/s390/entry/syscalls/syscall.tbl    |  4 ++--
 tools/perf/arch/x86/entry/syscalls/syscall_64.tbl  |  4 ++--
 17 files changed, 30 insertions(+), 46 deletions(-)

diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
index 734860ac7cf9d5..4a236493dca5b9 100644
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -301,9 +301,9 @@ __SYSCALL(__NR_flock, sys_flock)
 #define __NR_msync 144
 __SYSCALL(__NR_msync, sys_msync)
 #define __NR_readv 145
-__SYSCALL(__NR_readv, compat_sys_readv)
+__SYSCALL(__NR_readv, sys_readv)
 #define __NR_writev 146
-__SYSCALL(__NR_writev, compat_sys_writev)
+__SYSCALL(__NR_writev, sys_writev)
 #define __NR_getsid 147
 __SYSCALL(__NR_getsid, sys_getsid)
 #define __NR_fdatasync 148
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index f9df9edb67a407..c99a92646f8ee9 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -25,8 +25,8 @@
 15	n32	ioctl				compat_sys_ioctl
 16	n32	pread64				sys_pread64
 17	n32	pwrite64			sys_pwrite64
-18	n32	readv				compat_sys_readv
-19	n32	writev				compat_sys_writev
+18	n32	readv				sys_readv
+19	n32	writev				sys_writev
 20	n32	access				sys_access
 21	n32	pipe				sysm_pipe
 22	n32	_newselect			compat_sys_select
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index 195b43cf27c848..075064d10661bf 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -156,8 +156,8 @@
 142	o32	_newselect			sys_select			compat_sys_select
 143	o32	flock				sys_flock
 144	o32	msync				sys_msync
-145	o32	readv				sys_readv			compat_sys_readv
-146	o32	writev				sys_writev			compat_sys_writev
+145	o32	readv				sys_readv
+146	o32	writev				sys_writev
 147	o32	cacheflush			sys_cacheflush
 148	o32	cachectl			sys_cachectl
 149	o32	sysmips				__sys_sysmips
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index def64d221cd4fb..192abde0001d9d 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -159,8 +159,8 @@
 142	common	_newselect		sys_select			compat_sys_select
 143	common	flock			sys_flock
 144	common	msync			sys_msync
-145	common	readv			sys_readv			compat_sys_readv
-146	common	writev			sys_writev			compat_sys_writev
+145	common	readv			sys_readv
+146	common	writev			sys_writev
 147	common	getsid			sys_getsid
 148	common	fdatasync		sys_fdatasync
 149	common	_sysctl			sys_ni_syscall
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index c2d737ff2e7bec..6f1e2ecf0edad9 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -193,8 +193,8 @@
 142	common	_newselect			sys_select			compat_sys_select
 143	common	flock				sys_flock
 144	common	msync				sys_msync
-145	common	readv				sys_readv			compat_sys_readv
-146	common	writev				sys_writev			compat_sys_writev
+145	common	readv				sys_readv
+146	common	writev				sys_writev
 147	common	getsid				sys_getsid
 148	common	fdatasync			sys_fdatasync
 149	nospu	_sysctl				sys_ni_syscall
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index 10456bc936fb09..6101cf2e004cb4 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -134,8 +134,8 @@
 142  64		select			sys_select			-
 143  common	flock			sys_flock			sys_flock
 144  common	msync			sys_msync			sys_msync
-145  common	readv			sys_readv			compat_sys_readv
-146  common	writev			sys_writev			compat_sys_writev
+145  common	readv			sys_readv			sys_readv
+146  common	writev			sys_writev			sys_writev
 147  common	getsid			sys_getsid			sys_getsid
 148  common	fdatasync		sys_fdatasync			sys_fdatasync
 149  common	_sysctl			-				-
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index 4af114e84f2022..a87ddb282ab16f 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -149,8 +149,8 @@
 117	common	getrusage		sys_getrusage			compat_sys_getrusage
 118	common	getsockopt		sys_getsockopt			sys_getsockopt
 119	common	getcwd			sys_getcwd
-120	common	readv			sys_readv			compat_sys_readv
-121	common	writev			sys_writev			compat_sys_writev
+120	common	readv			sys_readv
+121	common	writev			sys_writev
 122	common	settimeofday		sys_settimeofday		compat_sys_settimeofday
 123	32	fchown			sys_fchown16
 123	64	fchown			sys_fchown
diff --git a/arch/x86/entry/syscall_x32.c b/arch/x86/entry/syscall_x32.c
index 1583831f61a9df..aa321444a41f63 100644
--- a/arch/x86/entry/syscall_x32.c
+++ b/arch/x86/entry/syscall_x32.c
@@ -12,6 +12,8 @@
  * Reuse the 64-bit entry points for the x32 versions that occupy different
  * slots in the syscall table.
  */
+#define __x32_sys_readv		__x64_sys_readv
+#define __x32_sys_writev	__x64_sys_writev
 #define __x32_sys_getsockopt	__x64_sys_getsockopt
 #define __x32_sys_setsockopt	__x64_sys_setsockopt
 
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 9d11028736661b..54ab4beb517f25 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -156,8 +156,8 @@
 142	i386	_newselect		sys_select			compat_sys_select
 143	i386	flock			sys_flock
 144	i386	msync			sys_msync
-145	i386	readv			sys_readv			compat_sys_readv
-146	i386	writev			sys_writev			compat_sys_writev
+145	i386	readv			sys_readv
+146	i386	writev			sys_writev
 147	i386	getsid			sys_getsid
 148	i386	fdatasync		sys_fdatasync
 149	i386	_sysctl			sys_ni_syscall
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index f30d6ae9a6883c..b1e59957c5c51c 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -371,8 +371,8 @@
 512	x32	rt_sigaction		compat_sys_rt_sigaction
 513	x32	rt_sigreturn		compat_sys_x32_rt_sigreturn
 514	x32	ioctl			compat_sys_ioctl
-515	x32	readv			compat_sys_readv
-516	x32	writev			compat_sys_writev
+515	x32	readv			sys_readv
+516	x32	writev			sys_writev
 517	x32	recvfrom		compat_sys_recvfrom
 518	x32	sendmsg			compat_sys_sendmsg
 519	x32	recvmsg			compat_sys_recvmsg
diff --git a/fs/read_write.c b/fs/read_write.c
index 9eb63c53da78f2..560d1b0bdef7bc 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1217,13 +1217,6 @@ SYSCALL_DEFINE6(pwritev2, unsigned long, fd, const struct iovec __user *, vec,
  * in_compat_syscall().
  */
 #ifdef CONFIG_COMPAT
-COMPAT_SYSCALL_DEFINE3(readv, compat_ulong_t, fd,
-		const struct iovec __user *, vec,
-		compat_ulong_t, vlen)
-{
-	return do_readv(fd, vec, vlen, 0);
-}
-
 #ifdef __ARCH_WANT_COMPAT_SYS_PREADV64
 COMPAT_SYSCALL_DEFINE4(preadv64, unsigned long, fd,
 		const struct iovec __user *, vec,
@@ -1265,13 +1258,6 @@ COMPAT_SYSCALL_DEFINE6(preadv2, compat_ulong_t, fd,
 	return do_preadv(fd, vec, vlen, pos, flags);
 }
 
-COMPAT_SYSCALL_DEFINE3(writev, compat_ulong_t, fd,
-		const struct iovec __user *, vec,
-		compat_ulong_t, vlen)
-{
-	return do_writev(fd, vec, vlen, 0);
-}
-
 #ifdef __ARCH_WANT_COMPAT_SYS_PWRITEV64
 COMPAT_SYSCALL_DEFINE4(pwritev64, unsigned long, fd,
 		const struct iovec __user *, vec,
diff --git a/include/linux/compat.h b/include/linux/compat.h
index ad6dc56e8828d6..0ff848234df8ba 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -545,10 +545,6 @@ asmlinkage long compat_sys_getdents(unsigned int fd,
 
 /* fs/read_write.c */
 asmlinkage long compat_sys_lseek(unsigned int, compat_off_t, unsigned int);
-asmlinkage ssize_t compat_sys_readv(compat_ulong_t fd,
-		const struct compat_iovec __user *vec, compat_ulong_t vlen);
-asmlinkage ssize_t compat_sys_writev(compat_ulong_t fd,
-		const struct compat_iovec __user *vec, compat_ulong_t vlen);
 /* No generic prototype for pread64 and pwrite64 */
 asmlinkage ssize_t compat_sys_preadv(compat_ulong_t fd,
 		const struct compat_iovec __user *vec,
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index 995b36c2ea7d8a..211c9eacbda6eb 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -207,9 +207,9 @@ __SYSCALL(__NR_read, sys_read)
 #define __NR_write 64
 __SYSCALL(__NR_write, sys_write)
 #define __NR_readv 65
-__SC_COMP(__NR_readv, sys_readv, compat_sys_readv)
+__SC_COMP(__NR_readv, sys_readv, sys_readv)
 #define __NR_writev 66
-__SC_COMP(__NR_writev, sys_writev, compat_sys_writev)
+__SC_COMP(__NR_writev, sys_writev, sys_writev)
 #define __NR_pread64 67
 __SC_COMP(__NR_pread64, sys_pread64, compat_sys_pread64)
 #define __NR_pwrite64 68
diff --git a/tools/include/uapi/asm-generic/unistd.h b/tools/include/uapi/asm-generic/unistd.h
index 995b36c2ea7d8a..211c9eacbda6eb 100644
--- a/tools/include/uapi/asm-generic/unistd.h
+++ b/tools/include/uapi/asm-generic/unistd.h
@@ -207,9 +207,9 @@ __SYSCALL(__NR_read, sys_read)
 #define __NR_write 64
 __SYSCALL(__NR_write, sys_write)
 #define __NR_readv 65
-__SC_COMP(__NR_readv, sys_readv, compat_sys_readv)
+__SC_COMP(__NR_readv, sys_readv, sys_readv)
 #define __NR_writev 66
-__SC_COMP(__NR_writev, sys_writev, compat_sys_writev)
+__SC_COMP(__NR_writev, sys_writev, sys_writev)
 #define __NR_pread64 67
 __SC_COMP(__NR_pread64, sys_pread64, compat_sys_pread64)
 #define __NR_pwrite64 68
diff --git a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
index 3ca6fe057a0b1f..46be68029587f9 100644
--- a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
+++ b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
@@ -189,8 +189,8 @@
 142	common	_newselect			sys_select			compat_sys_select
 143	common	flock				sys_flock
 144	common	msync				sys_msync
-145	common	readv				sys_readv			compat_sys_readv
-146	common	writev				sys_writev			compat_sys_writev
+145	common	readv				sys_readv
+146	common	writev				sys_writev
 147	common	getsid				sys_getsid
 148	common	fdatasync			sys_fdatasync
 149	nospu	_sysctl				sys_ni_syscall
diff --git a/tools/perf/arch/s390/entry/syscalls/syscall.tbl b/tools/perf/arch/s390/entry/syscalls/syscall.tbl
index 6a0bbea225db0d..fb5e61ce9d5838 100644
--- a/tools/perf/arch/s390/entry/syscalls/syscall.tbl
+++ b/tools/perf/arch/s390/entry/syscalls/syscall.tbl
@@ -134,8 +134,8 @@
 142  64		select			sys_select			-
 143  common	flock			sys_flock			sys_flock
 144  common	msync			sys_msync			compat_sys_msync
-145  common	readv			sys_readv			compat_sys_readv
-146  common	writev			sys_writev			compat_sys_writev
+145  common	readv			sys_readv
+146  common	writev			sys_writev
 147  common	getsid			sys_getsid			sys_getsid
 148  common	fdatasync		sys_fdatasync			sys_fdatasync
 149  common	_sysctl			-				-
diff --git a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
index f30d6ae9a6883c..b1e59957c5c51c 100644
--- a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
@@ -371,8 +371,8 @@
 512	x32	rt_sigaction		compat_sys_rt_sigaction
 513	x32	rt_sigreturn		compat_sys_x32_rt_sigreturn
 514	x32	ioctl			compat_sys_ioctl
-515	x32	readv			compat_sys_readv
-516	x32	writev			compat_sys_writev
+515	x32	readv			sys_readv
+516	x32	writev			sys_writev
 517	x32	recvfrom		compat_sys_recvfrom
 518	x32	sendmsg			compat_sys_sendmsg
 519	x32	recvmsg			compat_sys_recvmsg
-- 
2.28.0


^ permalink raw reply	[flat|nested] 67+ messages in thread

* [PATCH 7/9] fs: remove compat_sys_vmsplice
  2020-09-18 12:45 let import_iovec deal with compat_iovecs as well Christoph Hellwig
                   ` (5 preceding siblings ...)
  2020-09-18 12:45 ` [PATCH 6/9] fs: remove the compat readv/writev syscalls Christoph Hellwig
@ 2020-09-18 12:45 ` Christoph Hellwig
  2020-09-18 12:45 ` [PATCH 8/9] mm: remove compat_process_vm_{readv,writev} Christoph Hellwig
                   ` (2 subsequent siblings)
  9 siblings, 0 replies; 67+ messages in thread
From: Christoph Hellwig @ 2020-09-18 12:45 UTC (permalink / raw)
  To: Alexander Viro
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

Now that import_iovec handles compat iovecs, the native vmsplice syscall
can be used for the compat case as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/arm64/include/asm/unistd32.h             |  2 +-
 arch/mips/kernel/syscalls/syscall_n32.tbl     |  2 +-
 arch/mips/kernel/syscalls/syscall_o32.tbl     |  2 +-
 arch/parisc/kernel/syscalls/syscall.tbl       |  2 +-
 arch/powerpc/kernel/syscalls/syscall.tbl      |  2 +-
 arch/s390/kernel/syscalls/syscall.tbl         |  2 +-
 arch/sparc/kernel/syscalls/syscall.tbl        |  2 +-
 arch/x86/entry/syscall_x32.c                  |  1 +
 arch/x86/entry/syscalls/syscall_32.tbl        |  2 +-
 arch/x86/entry/syscalls/syscall_64.tbl        |  2 +-
 fs/splice.c                                   | 57 +++++--------------
 include/linux/compat.h                        |  4 --
 include/uapi/asm-generic/unistd.h             |  2 +-
 tools/include/uapi/asm-generic/unistd.h       |  2 +-
 .../arch/powerpc/entry/syscalls/syscall.tbl   |  2 +-
 .../perf/arch/s390/entry/syscalls/syscall.tbl |  2 +-
 .../arch/x86/entry/syscalls/syscall_64.tbl    |  2 +-
 17 files changed, 28 insertions(+), 62 deletions(-)

diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
index 4a236493dca5b9..11dfae3a8563bd 100644
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -697,7 +697,7 @@ __SYSCALL(__NR_sync_file_range2, compat_sys_aarch32_sync_file_range2)
 #define __NR_tee 342
 __SYSCALL(__NR_tee, sys_tee)
 #define __NR_vmsplice 343
-__SYSCALL(__NR_vmsplice, compat_sys_vmsplice)
+__SYSCALL(__NR_vmsplice, sys_vmsplice)
 #define __NR_move_pages 344
 __SYSCALL(__NR_move_pages, compat_sys_move_pages)
 #define __NR_getcpu 345
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index c99a92646f8ee9..5a39d4de0ac85b 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -278,7 +278,7 @@
 267	n32	splice				sys_splice
 268	n32	sync_file_range			sys_sync_file_range
 269	n32	tee				sys_tee
-270	n32	vmsplice			compat_sys_vmsplice
+270	n32	vmsplice			sys_vmsplice
 271	n32	move_pages			compat_sys_move_pages
 272	n32	set_robust_list			compat_sys_set_robust_list
 273	n32	get_robust_list			compat_sys_get_robust_list
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index 075064d10661bf..136efc6b8c5444 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -318,7 +318,7 @@
 304	o32	splice				sys_splice
 305	o32	sync_file_range			sys_sync_file_range		sys32_sync_file_range
 306	o32	tee				sys_tee
-307	o32	vmsplice			sys_vmsplice			compat_sys_vmsplice
+307	o32	vmsplice			sys_vmsplice
 308	o32	move_pages			sys_move_pages			compat_sys_move_pages
 309	o32	set_robust_list			sys_set_robust_list		compat_sys_set_robust_list
 310	o32	get_robust_list			sys_get_robust_list		compat_sys_get_robust_list
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index 192abde0001d9d..a9e184192caedd 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -330,7 +330,7 @@
 292	32	sync_file_range		parisc_sync_file_range
 292	64	sync_file_range		sys_sync_file_range
 293	common	tee			sys_tee
-294	common	vmsplice		sys_vmsplice			compat_sys_vmsplice
+294	common	vmsplice		sys_vmsplice
 295	common	move_pages		sys_move_pages			compat_sys_move_pages
 296	common	getcpu			sys_getcpu
 297	common	epoll_pwait		sys_epoll_pwait			compat_sys_epoll_pwait
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index 6f1e2ecf0edad9..0d4985919ca34d 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -369,7 +369,7 @@
 282	common	unshare				sys_unshare
 283	common	splice				sys_splice
 284	common	tee				sys_tee
-285	common	vmsplice			sys_vmsplice			compat_sys_vmsplice
+285	common	vmsplice			sys_vmsplice
 286	common	openat				sys_openat			compat_sys_openat
 287	common	mkdirat				sys_mkdirat
 288	common	mknodat				sys_mknodat
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index 6101cf2e004cb4..b5495a42814bd1 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -316,7 +316,7 @@
 306  common	splice			sys_splice			sys_splice
 307  common	sync_file_range		sys_sync_file_range		compat_sys_s390_sync_file_range
 308  common	tee			sys_tee				sys_tee
-309  common	vmsplice		sys_vmsplice			compat_sys_vmsplice
+309  common	vmsplice		sys_vmsplice			sys_vmsplice
 310  common	move_pages		sys_move_pages			compat_sys_move_pages
 311  common	getcpu			sys_getcpu			sys_getcpu
 312  common	epoll_pwait		sys_epoll_pwait			compat_sys_epoll_pwait
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index a87ddb282ab16f..f1810c1a35caa5 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -38,7 +38,7 @@
 23	64    	setuid			sys_setuid
 24	32	getuid			sys_getuid16
 24	64   	getuid			sys_getuid
-25	common	vmsplice		sys_vmsplice			compat_sys_vmsplice
+25	common	vmsplice		sys_vmsplice
 26	common	ptrace			sys_ptrace			compat_sys_ptrace
 27	common	alarm			sys_alarm
 28	common	sigaltstack		sys_sigaltstack			compat_sys_sigaltstack
diff --git a/arch/x86/entry/syscall_x32.c b/arch/x86/entry/syscall_x32.c
index aa321444a41f63..a4840b9d50ad14 100644
--- a/arch/x86/entry/syscall_x32.c
+++ b/arch/x86/entry/syscall_x32.c
@@ -16,6 +16,7 @@
 #define __x32_sys_writev	__x64_sys_writev
 #define __x32_sys_getsockopt	__x64_sys_getsockopt
 #define __x32_sys_setsockopt	__x64_sys_setsockopt
+#define __x32_sys_vmsplice	__x64_sys_vmsplice
 
 #define __SYSCALL_64(nr, sym)
 
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 54ab4beb517f25..0fb2f172581e51 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -327,7 +327,7 @@
 313	i386	splice			sys_splice
 314	i386	sync_file_range		sys_ia32_sync_file_range
 315	i386	tee			sys_tee
-316	i386	vmsplice		sys_vmsplice			compat_sys_vmsplice
+316	i386	vmsplice		sys_vmsplice
 317	i386	move_pages		sys_move_pages			compat_sys_move_pages
 318	i386	getcpu			sys_getcpu
 319	i386	epoll_pwait		sys_epoll_pwait
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index b1e59957c5c51c..642af919183de4 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -388,7 +388,7 @@
 529	x32	waitid			compat_sys_waitid
 530	x32	set_robust_list		compat_sys_set_robust_list
 531	x32	get_robust_list		compat_sys_get_robust_list
-532	x32	vmsplice		compat_sys_vmsplice
+532	x32	vmsplice		sys_vmsplice
 533	x32	move_pages		compat_sys_move_pages
 534	x32	preadv			compat_sys_preadv64
 535	x32	pwritev			compat_sys_pwritev64
diff --git a/fs/splice.c b/fs/splice.c
index 132d42b9871f9b..18d84544030b39 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -33,7 +33,6 @@
 #include <linux/security.h>
 #include <linux/gfp.h>
 #include <linux/socket.h>
-#include <linux/compat.h>
 #include <linux/sched/signal.h>
 
 #include "internal.h"
@@ -1332,20 +1331,6 @@ static int vmsplice_type(struct fd f, int *type)
  * Currently we punt and implement it as a normal copy, see pipe_to_user().
  *
  */
-static long do_vmsplice(struct file *f, struct iov_iter *iter, unsigned int flags)
-{
-	if (unlikely(flags & ~SPLICE_F_ALL))
-		return -EINVAL;
-
-	if (!iov_iter_count(iter))
-		return 0;
-
-	if (iov_iter_rw(iter) == WRITE)
-		return vmsplice_to_pipe(f, iter, flags);
-	else
-		return vmsplice_to_user(f, iter, flags);
-}
-
 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov,
 		unsigned long, nr_segs, unsigned int, flags)
 {
@@ -1356,6 +1341,9 @@ SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov,
 	struct fd f;
 	int type;
 
+	if (unlikely(flags & ~SPLICE_F_ALL))
+		return -EINVAL;
+
 	f = fdget(fd);
 	error = vmsplice_type(f, &type);
 	if (error)
@@ -1363,40 +1351,21 @@ SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov,
 
 	error = import_iovec(type, uiov, nr_segs,
 			     ARRAY_SIZE(iovstack), &iov, &iter);
-	if (error >= 0) {
-		error = do_vmsplice(f.file, &iter, flags);
-		kfree(iov);
-	}
-	fdput(f);
-	return error;
-}
+	if (error < 0)
+		goto out_fdput;
 
-#ifdef CONFIG_COMPAT
-COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
-		    unsigned int, nr_segs, unsigned int, flags)
-{
-	struct iovec iovstack[UIO_FASTIOV];
-	struct iovec *iov = iovstack;
-	struct iov_iter iter;
-	ssize_t error;
-	struct fd f;
-	int type;
-
-	f = fdget(fd);
-	error = vmsplice_type(f, &type);
-	if (error)
-		return error;
+	if (!iov_iter_count(&iter))
+		error = 0;
+	else if (iov_iter_rw(&iter) == WRITE)
+		error = vmsplice_to_pipe(f.file, &iter, flags);
+	else
+		error = vmsplice_to_user(f.file, &iter, flags);
 
-	error = import_iovec(type, (struct iovec __user *)iov32, nr_segs,
-			     ARRAY_SIZE(iovstack), &iov, &iter);
-	if (error >= 0) {
-		error = do_vmsplice(f.file, &iter, flags);
-		kfree(iov);
-	}
+	kfree(iov);
+out_fdput:
 	fdput(f);
 	return error;
 }
-#endif
 
 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
 		int, fd_out, loff_t __user *, off_out,
diff --git a/include/linux/compat.h b/include/linux/compat.h
index 0ff848234df8ba..a7af6ed06cb000 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -597,10 +597,6 @@ asmlinkage long compat_sys_signalfd4(int ufd,
 				     const compat_sigset_t __user *sigmask,
 				     compat_size_t sigsetsize, int flags);
 
-/* fs/splice.c */
-asmlinkage long compat_sys_vmsplice(int fd, const struct compat_iovec __user *,
-				    unsigned int nr_segs, unsigned int flags);
-
 /* fs/stat.c */
 asmlinkage long compat_sys_newfstatat(unsigned int dfd,
 				      const char __user *filename,
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index 211c9eacbda6eb..f2dcb0d5703014 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -237,7 +237,7 @@ __SC_COMP(__NR_signalfd4, sys_signalfd4, compat_sys_signalfd4)
 
 /* fs/splice.c */
 #define __NR_vmsplice 75
-__SC_COMP(__NR_vmsplice, sys_vmsplice, compat_sys_vmsplice)
+__SYSCALL(__NR_vmsplice, sys_vmsplice)
 #define __NR_splice 76
 __SYSCALL(__NR_splice, sys_splice)
 #define __NR_tee 77
diff --git a/tools/include/uapi/asm-generic/unistd.h b/tools/include/uapi/asm-generic/unistd.h
index 211c9eacbda6eb..f2dcb0d5703014 100644
--- a/tools/include/uapi/asm-generic/unistd.h
+++ b/tools/include/uapi/asm-generic/unistd.h
@@ -237,7 +237,7 @@ __SC_COMP(__NR_signalfd4, sys_signalfd4, compat_sys_signalfd4)
 
 /* fs/splice.c */
 #define __NR_vmsplice 75
-__SC_COMP(__NR_vmsplice, sys_vmsplice, compat_sys_vmsplice)
+__SYSCALL(__NR_vmsplice, sys_vmsplice)
 #define __NR_splice 76
 __SYSCALL(__NR_splice, sys_splice)
 #define __NR_tee 77
diff --git a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
index 46be68029587f9..26f0347c15118b 100644
--- a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
+++ b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
@@ -363,7 +363,7 @@
 282	common	unshare				sys_unshare
 283	common	splice				sys_splice
 284	common	tee				sys_tee
-285	common	vmsplice			sys_vmsplice			compat_sys_vmsplice
+285	common	vmsplice			sys_vmsplice
 286	common	openat				sys_openat			compat_sys_openat
 287	common	mkdirat				sys_mkdirat
 288	common	mknodat				sys_mknodat
diff --git a/tools/perf/arch/s390/entry/syscalls/syscall.tbl b/tools/perf/arch/s390/entry/syscalls/syscall.tbl
index fb5e61ce9d5838..02ad81f69bb7e3 100644
--- a/tools/perf/arch/s390/entry/syscalls/syscall.tbl
+++ b/tools/perf/arch/s390/entry/syscalls/syscall.tbl
@@ -316,7 +316,7 @@
 306  common	splice			sys_splice			compat_sys_splice
 307  common	sync_file_range		sys_sync_file_range		compat_sys_s390_sync_file_range
 308  common	tee			sys_tee				compat_sys_tee
-309  common	vmsplice		sys_vmsplice			compat_sys_vmsplice
+309  common	vmsplice		sys_vmsplice			sys_vmsplice
 310  common	move_pages		sys_move_pages			compat_sys_move_pages
 311  common	getcpu			sys_getcpu			compat_sys_getcpu
 312  common	epoll_pwait		sys_epoll_pwait			compat_sys_epoll_pwait
diff --git a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
index b1e59957c5c51c..642af919183de4 100644
--- a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
@@ -388,7 +388,7 @@
 529	x32	waitid			compat_sys_waitid
 530	x32	set_robust_list		compat_sys_set_robust_list
 531	x32	get_robust_list		compat_sys_get_robust_list
-532	x32	vmsplice		compat_sys_vmsplice
+532	x32	vmsplice		sys_vmsplice
 533	x32	move_pages		compat_sys_move_pages
 534	x32	preadv			compat_sys_preadv64
 535	x32	pwritev			compat_sys_pwritev64
-- 
2.28.0


^ permalink raw reply	[flat|nested] 67+ messages in thread

* [PATCH 8/9] mm: remove compat_process_vm_{readv,writev}
  2020-09-18 12:45 let import_iovec deal with compat_iovecs as well Christoph Hellwig
                   ` (6 preceding siblings ...)
  2020-09-18 12:45 ` [PATCH 7/9] fs: remove compat_sys_vmsplice Christoph Hellwig
@ 2020-09-18 12:45 ` Christoph Hellwig
  2020-09-18 13:48   ` Arnd Bergmann
  2020-09-18 12:45 ` [PATCH 9/9] security/keys: remove compat_keyctl_instantiate_key_iov Christoph Hellwig
  2020-09-19 14:24 ` let import_iovec deal with compat_iovecs as well David Laight
  9 siblings, 1 reply; 67+ messages in thread
From: Christoph Hellwig @ 2020-09-18 12:45 UTC (permalink / raw)
  To: Alexander Viro
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

Now that import_iovec handles compat iovecs, the native syscalls
can be used for the compat case as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/arm64/include/asm/unistd32.h             |  4 +-
 arch/mips/kernel/syscalls/syscall_n32.tbl     |  4 +-
 arch/mips/kernel/syscalls/syscall_o32.tbl     |  4 +-
 arch/parisc/kernel/syscalls/syscall.tbl       |  4 +-
 arch/powerpc/kernel/syscalls/syscall.tbl      |  4 +-
 arch/s390/kernel/syscalls/syscall.tbl         |  4 +-
 arch/sparc/kernel/syscalls/syscall.tbl        |  4 +-
 arch/x86/entry/syscall_x32.c                  |  2 +
 arch/x86/entry/syscalls/syscall_32.tbl        |  4 +-
 arch/x86/entry/syscalls/syscall_64.tbl        |  4 +-
 include/linux/compat.h                        |  8 ---
 include/uapi/asm-generic/unistd.h             |  6 +-
 mm/process_vm_access.c                        | 70 -------------------
 tools/include/uapi/asm-generic/unistd.h       |  6 +-
 .../arch/powerpc/entry/syscalls/syscall.tbl   |  4 +-
 .../perf/arch/s390/entry/syscalls/syscall.tbl |  4 +-
 .../arch/x86/entry/syscalls/syscall_64.tbl    |  4 +-
 17 files changed, 30 insertions(+), 110 deletions(-)

diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
index 11dfae3a8563bd..0c280a05f699bf 100644
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -763,9 +763,9 @@ __SYSCALL(__NR_sendmmsg, compat_sys_sendmmsg)
 #define __NR_setns 375
 __SYSCALL(__NR_setns, sys_setns)
 #define __NR_process_vm_readv 376
-__SYSCALL(__NR_process_vm_readv, compat_sys_process_vm_readv)
+__SYSCALL(__NR_process_vm_readv, sys_process_vm_readv)
 #define __NR_process_vm_writev 377
-__SYSCALL(__NR_process_vm_writev, compat_sys_process_vm_writev)
+__SYSCALL(__NR_process_vm_writev, sys_process_vm_writev)
 #define __NR_kcmp 378
 __SYSCALL(__NR_kcmp, sys_kcmp)
 #define __NR_finit_module 379
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index 5a39d4de0ac85b..0bc2e0fcf1ee56 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -317,8 +317,8 @@
 306	n32	syncfs				sys_syncfs
 307	n32	sendmmsg			compat_sys_sendmmsg
 308	n32	setns				sys_setns
-309	n32	process_vm_readv		compat_sys_process_vm_readv
-310	n32	process_vm_writev		compat_sys_process_vm_writev
+309	n32	process_vm_readv		sys_process_vm_readv
+310	n32	process_vm_writev		sys_process_vm_writev
 311	n32	kcmp				sys_kcmp
 312	n32	finit_module			sys_finit_module
 313	n32	sched_setattr			sys_sched_setattr
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index 136efc6b8c5444..b408c13b934296 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -356,8 +356,8 @@
 342	o32	syncfs				sys_syncfs
 343	o32	sendmmsg			sys_sendmmsg			compat_sys_sendmmsg
 344	o32	setns				sys_setns
-345	o32	process_vm_readv		sys_process_vm_readv		compat_sys_process_vm_readv
-346	o32	process_vm_writev		sys_process_vm_writev		compat_sys_process_vm_writev
+345	o32	process_vm_readv		sys_process_vm_readv
+346	o32	process_vm_writev		sys_process_vm_writev
 347	o32	kcmp				sys_kcmp
 348	o32	finit_module			sys_finit_module
 349	o32	sched_setattr			sys_sched_setattr
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index a9e184192caedd..2015a5124b78ad 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -372,8 +372,8 @@
 327	common	syncfs			sys_syncfs
 328	common	setns			sys_setns
 329	common	sendmmsg		sys_sendmmsg			compat_sys_sendmmsg
-330	common	process_vm_readv	sys_process_vm_readv		compat_sys_process_vm_readv
-331	common	process_vm_writev	sys_process_vm_writev		compat_sys_process_vm_writev
+330	common	process_vm_readv	sys_process_vm_readv
+331	common	process_vm_writev	sys_process_vm_writev
 332	common	kcmp			sys_kcmp
 333	common	finit_module		sys_finit_module
 334	common	sched_setattr		sys_sched_setattr
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index 0d4985919ca34d..66a472aa635d3f 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -449,8 +449,8 @@
 348	common	syncfs				sys_syncfs
 349	common	sendmmsg			sys_sendmmsg			compat_sys_sendmmsg
 350	common	setns				sys_setns
-351	nospu	process_vm_readv		sys_process_vm_readv		compat_sys_process_vm_readv
-352	nospu	process_vm_writev		sys_process_vm_writev		compat_sys_process_vm_writev
+351	nospu	process_vm_readv		sys_process_vm_readv
+352	nospu	process_vm_writev		sys_process_vm_writev
 353	nospu	finit_module			sys_finit_module
 354	nospu	kcmp				sys_kcmp
 355	common	sched_setattr			sys_sched_setattr
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index b5495a42814bd1..7485867a490bb2 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -347,8 +347,8 @@
 337  common	clock_adjtime		sys_clock_adjtime		sys_clock_adjtime32
 338  common	syncfs			sys_syncfs			sys_syncfs
 339  common	setns			sys_setns			sys_setns
-340  common	process_vm_readv	sys_process_vm_readv		compat_sys_process_vm_readv
-341  common	process_vm_writev	sys_process_vm_writev		compat_sys_process_vm_writev
+340  common	process_vm_readv	sys_process_vm_readv		sys_process_vm_readv
+341  common	process_vm_writev	sys_process_vm_writev		sys_process_vm_writev
 342  common	s390_runtime_instr	sys_s390_runtime_instr		sys_s390_runtime_instr
 343  common	kcmp			sys_kcmp			sys_kcmp
 344  common	finit_module		sys_finit_module		sys_finit_module
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index f1810c1a35caa5..4a9365b2e340b2 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -406,8 +406,8 @@
 335	common	syncfs			sys_syncfs
 336	common	sendmmsg		sys_sendmmsg			compat_sys_sendmmsg
 337	common	setns			sys_setns
-338	common	process_vm_readv	sys_process_vm_readv		compat_sys_process_vm_readv
-339	common	process_vm_writev	sys_process_vm_writev		compat_sys_process_vm_writev
+338	common	process_vm_readv	sys_process_vm_readv
+339	common	process_vm_writev	sys_process_vm_writev
 340	32	kern_features		sys_ni_syscall			sys_kern_features
 340	64	kern_features		sys_kern_features
 341	common	kcmp			sys_kcmp
diff --git a/arch/x86/entry/syscall_x32.c b/arch/x86/entry/syscall_x32.c
index a4840b9d50ad14..f2fe0a33bcfdd5 100644
--- a/arch/x86/entry/syscall_x32.c
+++ b/arch/x86/entry/syscall_x32.c
@@ -17,6 +17,8 @@
 #define __x32_sys_getsockopt	__x64_sys_getsockopt
 #define __x32_sys_setsockopt	__x64_sys_setsockopt
 #define __x32_sys_vmsplice	__x64_sys_vmsplice
+#define __x32_sys_process_vm_readv	__x64_sys_process_vm_readv
+#define __x32_sys_process_vm_writev	__x64_sys_process_vm_writev
 
 #define __SYSCALL_64(nr, sym)
 
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 0fb2f172581e51..5fbe10ad8a23fc 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -358,8 +358,8 @@
 344	i386	syncfs			sys_syncfs
 345	i386	sendmmsg		sys_sendmmsg			compat_sys_sendmmsg
 346	i386	setns			sys_setns
-347	i386	process_vm_readv	sys_process_vm_readv		compat_sys_process_vm_readv
-348	i386	process_vm_writev	sys_process_vm_writev		compat_sys_process_vm_writev
+347	i386	process_vm_readv	sys_process_vm_readv
+348	i386	process_vm_writev	sys_process_vm_writev
 349	i386	kcmp			sys_kcmp
 350	i386	finit_module		sys_finit_module
 351	i386	sched_setattr		sys_sched_setattr
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 642af919183de4..347809649ba28f 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -395,8 +395,8 @@
 536	x32	rt_tgsigqueueinfo	compat_sys_rt_tgsigqueueinfo
 537	x32	recvmmsg		compat_sys_recvmmsg_time64
 538	x32	sendmmsg		compat_sys_sendmmsg
-539	x32	process_vm_readv	compat_sys_process_vm_readv
-540	x32	process_vm_writev	compat_sys_process_vm_writev
+539	x32	process_vm_readv	sys_process_vm_readv
+540	x32	process_vm_writev	sys_process_vm_writev
 541	x32	setsockopt		sys_setsockopt
 542	x32	getsockopt		sys_getsockopt
 543	x32	io_setup		compat_sys_io_setup
diff --git a/include/linux/compat.h b/include/linux/compat.h
index a7af6ed06cb000..bbb065e09b058a 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -780,14 +780,6 @@ asmlinkage long compat_sys_open_by_handle_at(int mountdirfd,
 					     int flags);
 asmlinkage long compat_sys_sendmmsg(int fd, struct compat_mmsghdr __user *mmsg,
 				    unsigned vlen, unsigned int flags);
-asmlinkage ssize_t compat_sys_process_vm_readv(compat_pid_t pid,
-		const struct compat_iovec __user *lvec,
-		compat_ulong_t liovcnt, const struct compat_iovec __user *rvec,
-		compat_ulong_t riovcnt, compat_ulong_t flags);
-asmlinkage ssize_t compat_sys_process_vm_writev(compat_pid_t pid,
-		const struct compat_iovec __user *lvec,
-		compat_ulong_t liovcnt, const struct compat_iovec __user *rvec,
-		compat_ulong_t riovcnt, compat_ulong_t flags);
 asmlinkage long compat_sys_execveat(int dfd, const char __user *filename,
 		     const compat_uptr_t __user *argv,
 		     const compat_uptr_t __user *envp, int flags);
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index f2dcb0d5703014..c1dfe99c9c3f70 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -727,11 +727,9 @@ __SYSCALL(__NR_setns, sys_setns)
 #define __NR_sendmmsg 269
 __SC_COMP(__NR_sendmmsg, sys_sendmmsg, compat_sys_sendmmsg)
 #define __NR_process_vm_readv 270
-__SC_COMP(__NR_process_vm_readv, sys_process_vm_readv, \
-          compat_sys_process_vm_readv)
+__SYSCALL(__NR_process_vm_readv, sys_process_vm_readv)
 #define __NR_process_vm_writev 271
-__SC_COMP(__NR_process_vm_writev, sys_process_vm_writev, \
-          compat_sys_process_vm_writev)
+__SYSCALL(__NR_process_vm_writev, sys_process_vm_writev)
 #define __NR_kcmp 272
 __SYSCALL(__NR_kcmp, sys_kcmp)
 #define __NR_finit_module 273
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index f21feebbd48f39..752bb724f10efa 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -14,10 +14,6 @@
 #include <linux/slab.h>
 #include <linux/syscalls.h>
 
-#ifdef CONFIG_COMPAT
-#include <linux/compat.h>
-#endif
-
 /**
  * process_vm_rw_pages - read/write pages from task specified
  * @pages: array of pointers to pages we want to copy
@@ -307,69 +303,3 @@ SYSCALL_DEFINE6(process_vm_writev, pid_t, pid,
 {
 	return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1);
 }
-
-#ifdef CONFIG_COMPAT
-
-static ssize_t
-compat_process_vm_rw(compat_pid_t pid,
-		     const struct compat_iovec __user *lvec,
-		     unsigned long liovcnt,
-		     const struct compat_iovec __user *rvec,
-		     unsigned long riovcnt,
-		     unsigned long flags, int vm_write)
-{
-	struct iovec iovstack_l[UIO_FASTIOV];
-	struct iovec iovstack_r[UIO_FASTIOV];
-	struct iovec *iov_l = iovstack_l;
-	struct iovec *iov_r = iovstack_r;
-	struct iov_iter iter;
-	ssize_t rc = -EFAULT;
-	int dir = vm_write ? WRITE : READ;
-
-	if (flags != 0)
-		return -EINVAL;
-
-	rc = import_iovec(dir, (const struct iovec __user *)lvec, liovcnt,
-			  UIO_FASTIOV, &iov_l, &iter);
-	if (rc < 0)
-		return rc;
-	if (!iov_iter_count(&iter))
-		goto free_iovecs;
-	rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY,
-				   (const struct iovec __user *)rvec, riovcnt,
-				   UIO_FASTIOV, iovstack_r, &iov_r);
-	if (rc <= 0)
-		goto free_iovecs;
-
-	rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
-
-free_iovecs:
-	if (iov_r != iovstack_r)
-		kfree(iov_r);
-	kfree(iov_l);
-	return rc;
-}
-
-COMPAT_SYSCALL_DEFINE6(process_vm_readv, compat_pid_t, pid,
-		       const struct compat_iovec __user *, lvec,
-		       compat_ulong_t, liovcnt,
-		       const struct compat_iovec __user *, rvec,
-		       compat_ulong_t, riovcnt,
-		       compat_ulong_t, flags)
-{
-	return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
-				    riovcnt, flags, 0);
-}
-
-COMPAT_SYSCALL_DEFINE6(process_vm_writev, compat_pid_t, pid,
-		       const struct compat_iovec __user *, lvec,
-		       compat_ulong_t, liovcnt,
-		       const struct compat_iovec __user *, rvec,
-		       compat_ulong_t, riovcnt,
-		       compat_ulong_t, flags)
-{
-	return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
-				    riovcnt, flags, 1);
-}
-
-#endif
diff --git a/tools/include/uapi/asm-generic/unistd.h b/tools/include/uapi/asm-generic/unistd.h
index f2dcb0d5703014..c1dfe99c9c3f70 100644
--- a/tools/include/uapi/asm-generic/unistd.h
+++ b/tools/include/uapi/asm-generic/unistd.h
@@ -727,11 +727,9 @@ __SYSCALL(__NR_setns, sys_setns)
 #define __NR_sendmmsg 269
 __SC_COMP(__NR_sendmmsg, sys_sendmmsg, compat_sys_sendmmsg)
 #define __NR_process_vm_readv 270
-__SC_COMP(__NR_process_vm_readv, sys_process_vm_readv, \
-          compat_sys_process_vm_readv)
+__SYSCALL(__NR_process_vm_readv, sys_process_vm_readv)
 #define __NR_process_vm_writev 271
-__SC_COMP(__NR_process_vm_writev, sys_process_vm_writev, \
-          compat_sys_process_vm_writev)
+__SYSCALL(__NR_process_vm_writev, sys_process_vm_writev)
 #define __NR_kcmp 272
 __SYSCALL(__NR_kcmp, sys_kcmp)
 #define __NR_finit_module 273
diff --git a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
index 26f0347c15118b..a188f053cbf90a 100644
--- a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
+++ b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
@@ -443,8 +443,8 @@
 348	common	syncfs				sys_syncfs
 349	common	sendmmsg			sys_sendmmsg			compat_sys_sendmmsg
 350	common	setns				sys_setns
-351	nospu	process_vm_readv		sys_process_vm_readv		compat_sys_process_vm_readv
-352	nospu	process_vm_writev		sys_process_vm_writev		compat_sys_process_vm_writev
+351	nospu	process_vm_readv		sys_process_vm_readv
+352	nospu	process_vm_writev		sys_process_vm_writev
 353	nospu	finit_module			sys_finit_module
 354	nospu	kcmp				sys_kcmp
 355	common	sched_setattr			sys_sched_setattr
diff --git a/tools/perf/arch/s390/entry/syscalls/syscall.tbl b/tools/perf/arch/s390/entry/syscalls/syscall.tbl
index 02ad81f69bb7e3..c44c83032c3a04 100644
--- a/tools/perf/arch/s390/entry/syscalls/syscall.tbl
+++ b/tools/perf/arch/s390/entry/syscalls/syscall.tbl
@@ -347,8 +347,8 @@
 337  common	clock_adjtime		sys_clock_adjtime		compat_sys_clock_adjtime
 338  common	syncfs			sys_syncfs			sys_syncfs
 339  common	setns			sys_setns			sys_setns
-340  common	process_vm_readv	sys_process_vm_readv		compat_sys_process_vm_readv
-341  common	process_vm_writev	sys_process_vm_writev		compat_sys_process_vm_writev
+340  common	process_vm_readv	sys_process_vm_readv		sys_process_vm_readv
+341  common	process_vm_writev	sys_process_vm_writev		sys_process_vm_writev
 342  common	s390_runtime_instr	sys_s390_runtime_instr		sys_s390_runtime_instr
 343  common	kcmp			sys_kcmp			compat_sys_kcmp
 344  common	finit_module		sys_finit_module		compat_sys_finit_module
diff --git a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
index 642af919183de4..347809649ba28f 100644
--- a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
@@ -395,8 +395,8 @@
 536	x32	rt_tgsigqueueinfo	compat_sys_rt_tgsigqueueinfo
 537	x32	recvmmsg		compat_sys_recvmmsg_time64
 538	x32	sendmmsg		compat_sys_sendmmsg
-539	x32	process_vm_readv	compat_sys_process_vm_readv
-540	x32	process_vm_writev	compat_sys_process_vm_writev
+539	x32	process_vm_readv	sys_process_vm_readv
+540	x32	process_vm_writev	sys_process_vm_writev
 541	x32	setsockopt		sys_setsockopt
 542	x32	getsockopt		sys_getsockopt
 543	x32	io_setup		compat_sys_io_setup
-- 
2.28.0


^ permalink raw reply	[flat|nested] 67+ messages in thread

* [PATCH 9/9] security/keys: remove compat_keyctl_instantiate_key_iov
  2020-09-18 12:45 let import_iovec deal with compat_iovecs as well Christoph Hellwig
                   ` (7 preceding siblings ...)
  2020-09-18 12:45 ` [PATCH 8/9] mm: remove compat_process_vm_{readv,writev} Christoph Hellwig
@ 2020-09-18 12:45 ` Christoph Hellwig
  2020-09-19 14:24 ` let import_iovec deal with compat_iovecs as well David Laight
  9 siblings, 0 replies; 67+ messages in thread
From: Christoph Hellwig @ 2020-09-18 12:45 UTC (permalink / raw)
  To: Alexander Viro
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

Now that import_iovec handles compat iovecs, the native version of
keyctl_instantiate_key_iov can be used for the compat case as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 security/keys/compat.c   | 36 ++----------------------------------
 security/keys/internal.h |  5 -----
 security/keys/keyctl.c   |  2 +-
 3 files changed, 3 insertions(+), 40 deletions(-)

diff --git a/security/keys/compat.c b/security/keys/compat.c
index 7ae531db031cf8..1545efdca56227 100644
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -11,38 +11,6 @@
 #include <linux/slab.h>
 #include "internal.h"
 
-/*
- * Instantiate a key with the specified compatibility multipart payload and
- * link the key into the destination keyring if one is given.
- *
- * The caller must have the appropriate instantiation permit set for this to
- * work (see keyctl_assume_authority).  No other permissions are required.
- *
- * If successful, 0 will be returned.
- */
-static long compat_keyctl_instantiate_key_iov(
-	key_serial_t id,
-	const struct compat_iovec __user *_payload_iov,
-	unsigned ioc,
-	key_serial_t ringid)
-{
-	struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
-	struct iov_iter from;
-	long ret;
-
-	if (!_payload_iov)
-		ioc = 0;
-
-	ret = import_iovec(WRITE, (const struct iovec __user *)_payload_iov,
-			   ioc, ARRAY_SIZE(iovstack), &iov, &from);
-	if (ret < 0)
-		return ret;
-
-	ret = keyctl_instantiate_key_common(id, &from, ringid);
-	kfree(iov);
-	return ret;
-}
-
 /*
  * The key control system call, 32-bit compatibility version for 64-bit archs
  */
@@ -113,8 +81,8 @@ COMPAT_SYSCALL_DEFINE5(keyctl, u32, option,
 		return keyctl_reject_key(arg2, arg3, arg4, arg5);
 
 	case KEYCTL_INSTANTIATE_IOV:
-		return compat_keyctl_instantiate_key_iov(
-			arg2, compat_ptr(arg3), arg4, arg5);
+		return keyctl_instantiate_key_iov(arg2, compat_ptr(arg3), arg4,
+						  arg5);
 
 	case KEYCTL_INVALIDATE:
 		return keyctl_invalidate_key(arg2);
diff --git a/security/keys/internal.h b/security/keys/internal.h
index 338a526cbfa516..9b9cf3b6fcbb4d 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -262,11 +262,6 @@ extern long keyctl_instantiate_key_iov(key_serial_t,
 				       const struct iovec __user *,
 				       unsigned, key_serial_t);
 extern long keyctl_invalidate_key(key_serial_t);
-
-struct iov_iter;
-extern long keyctl_instantiate_key_common(key_serial_t,
-					  struct iov_iter *,
-					  key_serial_t);
 extern long keyctl_restrict_keyring(key_serial_t id,
 				    const char __user *_type,
 				    const char __user *_restriction);
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 9febd37a168fd0..e26bbccda7ccee 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1164,7 +1164,7 @@ static int keyctl_change_reqkey_auth(struct key *key)
  *
  * If successful, 0 will be returned.
  */
-long keyctl_instantiate_key_common(key_serial_t id,
+static long keyctl_instantiate_key_common(key_serial_t id,
 				   struct iov_iter *from,
 				   key_serial_t ringid)
 {
-- 
2.28.0


^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 3/9] fs: explicitly check for CHECK_IOVEC_ONLY in rw_copy_check_uvector
  2020-09-18 12:45 ` [PATCH 3/9] fs: explicitly check for CHECK_IOVEC_ONLY in rw_copy_check_uvector Christoph Hellwig
@ 2020-09-18 12:56   ` Matthew Wilcox
  2020-09-18 13:39   ` Johannes Thumshirn
  1 sibling, 0 replies; 67+ messages in thread
From: Matthew Wilcox @ 2020-09-18 12:56 UTC (permalink / raw)
  To: Christoph Hellwig
  Cc: Alexander Viro, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

On Fri, Sep 18, 2020 at 02:45:27PM +0200, Christoph Hellwig wrote:
>  		}
> -		if (type >= 0
> -		    && unlikely(!access_ok(buf, len))) {
> +		if (type != CHECK_IOVEC_ONLY && unlikely(!access_ok(buf, len))) {

drop the unlikely() at the same time?  if it's really advantageous,
that should be embedded in the access_ok macro.


^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 2/9] compat.h: fix a spelling error in <linux/compat.h>
  2020-09-18 12:45 ` [PATCH 2/9] compat.h: fix a spelling error in <linux/compat.h> Christoph Hellwig
@ 2020-09-18 13:37   ` Johannes Thumshirn
  0 siblings, 0 replies; 67+ messages in thread
From: Johannes Thumshirn @ 2020-09-18 13:37 UTC (permalink / raw)
  To: Christoph Hellwig, Alexander Viro
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

On 18/09/2020 14:48, Christoph Hellwig wrote:
> We only have not compat_sys_readv64v2 syscall, only a
We have no?

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 3/9] fs: explicitly check for CHECK_IOVEC_ONLY in rw_copy_check_uvector
  2020-09-18 12:45 ` [PATCH 3/9] fs: explicitly check for CHECK_IOVEC_ONLY in rw_copy_check_uvector Christoph Hellwig
  2020-09-18 12:56   ` Matthew Wilcox
@ 2020-09-18 13:39   ` Johannes Thumshirn
  1 sibling, 0 replies; 67+ messages in thread
From: Johannes Thumshirn @ 2020-09-18 13:39 UTC (permalink / raw)
  To: Christoph Hellwig, Alexander Viro
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

Looks good,
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-18 12:45 ` [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag Christoph Hellwig
@ 2020-09-18 13:40   ` Al Viro
  2020-09-18 13:44     ` Christoph Hellwig
  2020-09-20 15:15   ` Matthew Wilcox
  1 sibling, 1 reply; 67+ messages in thread
From: Al Viro @ 2020-09-18 13:40 UTC (permalink / raw)
  To: Christoph Hellwig
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

On Fri, Sep 18, 2020 at 02:45:25PM +0200, Christoph Hellwig wrote:
> Add a flag to force processing a syscall as a compat syscall.  This is
> required so that in_compat_syscall() works for I/O submitted by io_uring
> helper threads on behalf of compat syscalls.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  arch/sparc/include/asm/compat.h | 3 ++-
>  arch/x86/include/asm/compat.h   | 2 +-
>  fs/io_uring.c                   | 9 +++++++++
>  include/linux/compat.h          | 5 ++++-
>  include/linux/sched.h           | 1 +
>  5 files changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/sparc/include/asm/compat.h b/arch/sparc/include/asm/compat.h
> index 40a267b3bd5208..fee6c51d36e869 100644
> --- a/arch/sparc/include/asm/compat.h
> +++ b/arch/sparc/include/asm/compat.h
> @@ -211,7 +211,8 @@ static inline int is_compat_task(void)
>  static inline bool in_compat_syscall(void)
>  {
>  	/* Vector 0x110 is LINUX_32BIT_SYSCALL_TRAP */
> -	return pt_regs_trap_type(current_pt_regs()) == 0x110;
> +	return pt_regs_trap_type(current_pt_regs()) == 0x110 ||
> +		(current->flags & PF_FORCE_COMPAT);

Can't say I like that approach ;-/  Reasoning about the behaviour is much
harder when it's controlled like that - witness set_fs() shite...

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-18 13:40   ` Al Viro
@ 2020-09-18 13:44     ` Christoph Hellwig
  2020-09-18 13:58       ` Al Viro
  2020-09-18 13:59       ` Arnd Bergmann
  0 siblings, 2 replies; 67+ messages in thread
From: Christoph Hellwig @ 2020-09-18 13:44 UTC (permalink / raw)
  To: Al Viro
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

On Fri, Sep 18, 2020 at 02:40:12PM +0100, Al Viro wrote:
> >  	/* Vector 0x110 is LINUX_32BIT_SYSCALL_TRAP */
> > -	return pt_regs_trap_type(current_pt_regs()) == 0x110;
> > +	return pt_regs_trap_type(current_pt_regs()) == 0x110 ||
> > +		(current->flags & PF_FORCE_COMPAT);
> 
> Can't say I like that approach ;-/  Reasoning about the behaviour is much
> harder when it's controlled like that - witness set_fs() shite...

I don't particularly like it either.  But do you have a better idea
how to deal with io_uring vs compat tasks?

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 8/9] mm: remove compat_process_vm_{readv,writev}
  2020-09-18 12:45 ` [PATCH 8/9] mm: remove compat_process_vm_{readv,writev} Christoph Hellwig
@ 2020-09-18 13:48   ` Arnd Bergmann
  0 siblings, 0 replies; 67+ messages in thread
From: Arnd Bergmann @ 2020-09-18 13:48 UTC (permalink / raw)
  To: Christoph Hellwig
  Cc: Alexander Viro, Andrew Morton, Jens Axboe, David Howells,
	Linux ARM, the arch/x86 maintainers, linux-kernel,
	open list:BROADCOM NVRAM DRIVER, Parisc List, linuxppc-dev,
	linux-s390, sparclinux, linux-block, linux-scsi,
	Linux FS-devel Mailing List, linux-aio, io-uring, linux-arch,
	Linux-MM, Networking, keyrings, LSM List

On Fri, Sep 18, 2020 at 2:45 PM Christoph Hellwig <hch@lst.de> wrote:
>
> Now that import_iovec handles compat iovecs, the native syscalls
> can be used for the compat case as well.
>
> diff --git a/arch/x86/entry/syscall_x32.c b/arch/x86/entry/syscall_x32.c
> index a4840b9d50ad14..f2fe0a33bcfdd5 100644
> --- a/arch/x86/entry/syscall_x32.c
> +++ b/arch/x86/entry/syscall_x32.c
> @@ -17,6 +17,8 @@
>  #define __x32_sys_getsockopt   __x64_sys_getsockopt
>  #define __x32_sys_setsockopt   __x64_sys_setsockopt
>  #define __x32_sys_vmsplice     __x64_sys_vmsplice
> +#define __x32_sys_process_vm_readv     __x64_sys_process_vm_readv
> +#define __x32_sys_process_vm_writev    __x64_sys_process_vm_writev
>
>  #define __SYSCALL_64(nr, sym)
>

I forgot this hack existed, and just sent a patch with subject "x86: add
__X32_COND_SYSCALL() macro" instead.

If I understand this right, the macros above should no longer be needed
once my patch gets merged.

        Arnd

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-18 13:44     ` Christoph Hellwig
@ 2020-09-18 13:58       ` Al Viro
  2020-09-18 15:16         ` Christoph Hellwig
  2020-09-19 14:53         ` David Laight
  2020-09-18 13:59       ` Arnd Bergmann
  1 sibling, 2 replies; 67+ messages in thread
From: Al Viro @ 2020-09-18 13:58 UTC (permalink / raw)
  To: Christoph Hellwig
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

On Fri, Sep 18, 2020 at 03:44:06PM +0200, Christoph Hellwig wrote:
> On Fri, Sep 18, 2020 at 02:40:12PM +0100, Al Viro wrote:
> > >  	/* Vector 0x110 is LINUX_32BIT_SYSCALL_TRAP */
> > > -	return pt_regs_trap_type(current_pt_regs()) == 0x110;
> > > +	return pt_regs_trap_type(current_pt_regs()) == 0x110 ||
> > > +		(current->flags & PF_FORCE_COMPAT);
> > 
> > Can't say I like that approach ;-/  Reasoning about the behaviour is much
> > harder when it's controlled like that - witness set_fs() shite...
> 
> I don't particularly like it either.  But do you have a better idea
> how to deal with io_uring vs compat tasks?

<wry> git rm fs/io_uring.c would make a good starting point </wry>
Yes, I know it's not going to happen, but one can dream...

Said that, why not provide a variant that would take an explicit
"is it compat" argument and use it there?  And have the normal
one pass in_compat_syscall() to that...

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-18 13:44     ` Christoph Hellwig
  2020-09-18 13:58       ` Al Viro
@ 2020-09-18 13:59       ` Arnd Bergmann
  1 sibling, 0 replies; 67+ messages in thread
From: Arnd Bergmann @ 2020-09-18 13:59 UTC (permalink / raw)
  To: Christoph Hellwig
  Cc: Al Viro, Andrew Morton, Jens Axboe, David Howells, Linux ARM,
	the arch/x86 maintainers, linux-kernel,
	open list:BROADCOM NVRAM DRIVER, Parisc List, linuxppc-dev,
	linux-s390, sparclinux, linux-block, linux-scsi,
	Linux FS-devel Mailing List, linux-aio, io-uring, linux-arch,
	Linux-MM, Networking, keyrings, LSM List

On Fri, Sep 18, 2020 at 3:44 PM Christoph Hellwig <hch@lst.de> wrote:
>
> On Fri, Sep 18, 2020 at 02:40:12PM +0100, Al Viro wrote:
> > >     /* Vector 0x110 is LINUX_32BIT_SYSCALL_TRAP */
> > > -   return pt_regs_trap_type(current_pt_regs()) == 0x110;
> > > +   return pt_regs_trap_type(current_pt_regs()) == 0x110 ||
> > > +           (current->flags & PF_FORCE_COMPAT);
> >
> > Can't say I like that approach ;-/  Reasoning about the behaviour is much
> > harder when it's controlled like that - witness set_fs() shite...
>
> I don't particularly like it either.  But do you have a better idea
> how to deal with io_uring vs compat tasks?

Do we need to worry about something other than the compat_iovec
struct for now? Regarding the code in io_import_iovec(), it would
seem that can easily be handled by exposing an internal helper.
Instead of

#ifdef CONFIG_COMPAT
     if (req->ctx->compat)
            return compat_import_iovec(rw, buf, sqe_len, UIO_FASTIOV,
iovec, iter);
#endif
        return import_iovec(rw, buf, sqe_len, UIO_FASTIOV, iovec, iter);

This could do

    __import_iovec(rw, buf, sqe_len, UIO_FASTIOV, iovec,
                     iter, req->ctx->compat);

With the normal import_iovec() becoming a trivial wrapper around
the same thing:

ssize_t import_iovec(int type, const struct iovec __user * uvector,
                 unsigned nr_segs, unsigned fast_segs,
                 struct iovec **iov, struct iov_iter *i)
{
     return __import_iovec(type, uvector, nr_segs, fast_segs, iov,
              i, in_compat_syscall());
}


         Arnd

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-18 13:58       ` Al Viro
@ 2020-09-18 15:16         ` Christoph Hellwig
  2020-09-19 16:21           ` Andy Lutomirski
  2020-09-19 22:09           ` Al Viro
  2020-09-19 14:53         ` David Laight
  1 sibling, 2 replies; 67+ messages in thread
From: Christoph Hellwig @ 2020-09-18 15:16 UTC (permalink / raw)
  To: Al Viro
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
> Said that, why not provide a variant that would take an explicit
> "is it compat" argument and use it there?  And have the normal
> one pass in_compat_syscall() to that...

That would help to not introduce a regression with this series yes.
But it wouldn't fix existing bugs when io_uring is used to access
read or write methods that use in_compat_syscall().  One example that
I recently ran into is drivers/scsi/sg.c.

^ permalink raw reply	[flat|nested] 67+ messages in thread

* RE: let import_iovec deal with compat_iovecs as well
  2020-09-18 12:45 let import_iovec deal with compat_iovecs as well Christoph Hellwig
                   ` (8 preceding siblings ...)
  2020-09-18 12:45 ` [PATCH 9/9] security/keys: remove compat_keyctl_instantiate_key_iov Christoph Hellwig
@ 2020-09-19 14:24 ` David Laight
  2020-09-21  4:41   ` 'Christoph Hellwig'
  9 siblings, 1 reply; 67+ messages in thread
From: David Laight @ 2020-09-19 14:24 UTC (permalink / raw)
  To: 'Christoph Hellwig', Alexander Viro
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

From: Christoph Hellwig
> Sent: 18 September 2020 13:45
> 
> this series changes import_iovec to transparently deal with comat iovec
> structures, and then cleanups up a lot of code dupliation.  But to get
> there it first has to fix the pre-existing bug that io_uring compat
> contexts don't trigger the in_compat_syscall() check.  This has so far
> been relatively harmless as very little code callable from io_uring used
> the check, and even that code that could be called usually wasn't.

I thought about that change while writing my import_iovec() => iovec_import()
patch - and thought that the io_uring code would (as usual) cause grief.

Christoph - did you see those patches?
	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)


^ permalink raw reply	[flat|nested] 67+ messages in thread

* RE: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-18 13:58       ` Al Viro
  2020-09-18 15:16         ` Christoph Hellwig
@ 2020-09-19 14:53         ` David Laight
  1 sibling, 0 replies; 67+ messages in thread
From: David Laight @ 2020-09-19 14:53 UTC (permalink / raw)
  To: 'Al Viro', Christoph Hellwig
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

From: Al Viro
> Sent: 18 September 2020 14:58
> 
> On Fri, Sep 18, 2020 at 03:44:06PM +0200, Christoph Hellwig wrote:
> > On Fri, Sep 18, 2020 at 02:40:12PM +0100, Al Viro wrote:
> > > >  	/* Vector 0x110 is LINUX_32BIT_SYSCALL_TRAP */
> > > > -	return pt_regs_trap_type(current_pt_regs()) == 0x110;
> > > > +	return pt_regs_trap_type(current_pt_regs()) == 0x110 ||
> > > > +		(current->flags & PF_FORCE_COMPAT);
> > >
> > > Can't say I like that approach ;-/  Reasoning about the behaviour is much
> > > harder when it's controlled like that - witness set_fs() shite...
> >
> > I don't particularly like it either.  But do you have a better idea
> > how to deal with io_uring vs compat tasks?
> 
> <wry> git rm fs/io_uring.c would make a good starting point </wry>
> Yes, I know it's not going to happen, but one can dream...

Maybe the io_uring code needs some changes to make it vaguely safe.
- No support for 32-bit compat mixed working (or at all?).
  Plausibly a special worker could do 32bit work.
- ring structure (I'm assuming mapped by mmap()) never mapped
  in more than one process (not cloned by fork()).
- No implicit handover of files to another process.
  Would need an munmap, handover, mmap sequence.

In any case the io_ring rather abuses the import_iovec() interface.

The canonical sequence is (types from memory):
	struct iovec cache[8], *iov = cache;
	struct iter iter;
	...
	rval = import_iovec(..., &iov, 8, &iter);
	// Do read/write user using 'iter'
	free(iov);

I don't think there is any strict requirement that iter.iov
is set to either 'cache' or 'iov' (it probably must point
into one of them.)
But the io_uring code will make that assumption because the
actual copies can be done much later and it doesn't save 'iter'.
It gets itself in a right mess because it doesn't separate
the 'address I need to free' from 'the iov[] for any transfers'.

io_uring is also the only code that relies on import_iovec()
returning the iter.count on success.
It would be much better to have:
	iov = import_iovec(..., &cache, ...);
	free(iov);
and use ERR_PTR() et al for error detectoion.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)


^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-18 15:16         ` Christoph Hellwig
@ 2020-09-19 16:21           ` Andy Lutomirski
  2020-09-19 21:16             ` Arnd Bergmann
  2020-09-19 22:09           ` Al Viro
  1 sibling, 1 reply; 67+ messages in thread
From: Andy Lutomirski @ 2020-09-19 16:21 UTC (permalink / raw)
  To: Christoph Hellwig
  Cc: Al Viro, Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, X86 ML, LKML, open list:MIPS, Parisc List,
	linuxppc-dev, linux-s390, sparclinux, linux-block,
	Linux SCSI List, Linux FS Devel, linux-aio, io-uring, linux-arch,
	Linux-MM, Network Development, keyrings, LSM List

On Fri, Sep 18, 2020 at 8:16 AM Christoph Hellwig <hch@lst.de> wrote:
>
> On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
> > Said that, why not provide a variant that would take an explicit
> > "is it compat" argument and use it there?  And have the normal
> > one pass in_compat_syscall() to that...
>
> That would help to not introduce a regression with this series yes.
> But it wouldn't fix existing bugs when io_uring is used to access
> read or write methods that use in_compat_syscall().  One example that
> I recently ran into is drivers/scsi/sg.c.

Aside from the potentially nasty use of per-task variables, one thing
I don't like about PF_FORCE_COMPAT is that it's one-way.  If we're
going to have a generic mechanism for this, shouldn't we allow a full
override of the syscall arch instead of just allowing forcing compat
so that a compat syscall can do a non-compat operation?

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-19 16:21           ` Andy Lutomirski
@ 2020-09-19 21:16             ` Arnd Bergmann
  2020-09-19 21:52               ` Finn Thain
  2020-09-19 22:22               ` Andy Lutomirski
  0 siblings, 2 replies; 67+ messages in thread
From: Arnd Bergmann @ 2020-09-19 21:16 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: Christoph Hellwig, Al Viro, Andrew Morton, Jens Axboe,
	David Howells, linux-arm-kernel, X86 ML, LKML, open list:MIPS,
	Parisc List, linuxppc-dev, linux-s390, sparclinux, linux-block,
	Linux SCSI List, Linux FS Devel, linux-aio, io-uring, linux-arch,
	Linux-MM, Network Development, keyrings, LSM List

On Sat, Sep 19, 2020 at 6:21 PM Andy Lutomirski <luto@kernel.org> wrote:
> On Fri, Sep 18, 2020 at 8:16 AM Christoph Hellwig <hch@lst.de> wrote:
> > On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
> > > Said that, why not provide a variant that would take an explicit
> > > "is it compat" argument and use it there?  And have the normal
> > > one pass in_compat_syscall() to that...
> >
> > That would help to not introduce a regression with this series yes.
> > But it wouldn't fix existing bugs when io_uring is used to access
> > read or write methods that use in_compat_syscall().  One example that
> > I recently ran into is drivers/scsi/sg.c.

Ah, so reading /dev/input/event* would suffer from the same issue,
and that one would in fact be broken by your patch in the hypothetical
case that someone tried to use io_uring to read /dev/input/event on x32...

For reference, I checked the socket timestamp handling that has a
number of corner cases with time32/time64 formats in compat mode,
but none of those appear to be affected by the problem.

> Aside from the potentially nasty use of per-task variables, one thing
> I don't like about PF_FORCE_COMPAT is that it's one-way.  If we're
> going to have a generic mechanism for this, shouldn't we allow a full
> override of the syscall arch instead of just allowing forcing compat
> so that a compat syscall can do a non-compat operation?

The only reason it's needed here is that the caller is in a kernel
thread rather than a system call. Are there any possible scenarios
where one would actually need the opposite?

       Arnd

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-19 21:16             ` Arnd Bergmann
@ 2020-09-19 21:52               ` Finn Thain
  2020-09-19 22:22               ` Andy Lutomirski
  1 sibling, 0 replies; 67+ messages in thread
From: Finn Thain @ 2020-09-19 21:52 UTC (permalink / raw)
  To: Arnd Bergmann
  Cc: Peter Maydell, Andy Lutomirski, Christoph Hellwig, Al Viro,
	Andrew Morton, Jens Axboe, David Howells, linux-arm-kernel,
	X86 ML, LKML, open list:MIPS, Parisc List, linuxppc-dev,
	linux-s390, sparclinux, linux-block, Linux SCSI List,
	Linux FS Devel, linux-aio, io-uring, linux-arch, Linux-MM,
	Network Development, keyrings, LSM List

On Sat, 19 Sep 2020, Arnd Bergmann wrote:

> On Sat, Sep 19, 2020 at 6:21 PM Andy Lutomirski <luto@kernel.org> wrote:
> > On Fri, Sep 18, 2020 at 8:16 AM Christoph Hellwig <hch@lst.de> wrote:
> > > On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
> > > > Said that, why not provide a variant that would take an explicit 
> > > > "is it compat" argument and use it there?  And have the normal one 
> > > > pass in_compat_syscall() to that...
> > >
> > > That would help to not introduce a regression with this series yes. 
> > > But it wouldn't fix existing bugs when io_uring is used to access 
> > > read or write methods that use in_compat_syscall().  One example 
> > > that I recently ran into is drivers/scsi/sg.c.
> 
> Ah, so reading /dev/input/event* would suffer from the same issue, and 
> that one would in fact be broken by your patch in the hypothetical case 
> that someone tried to use io_uring to read /dev/input/event on x32...
> 
> For reference, I checked the socket timestamp handling that has a number 
> of corner cases with time32/time64 formats in compat mode, but none of 
> those appear to be affected by the problem.
> 
> > Aside from the potentially nasty use of per-task variables, one thing 
> > I don't like about PF_FORCE_COMPAT is that it's one-way.  If we're 
> > going to have a generic mechanism for this, shouldn't we allow a full 
> > override of the syscall arch instead of just allowing forcing compat 
> > so that a compat syscall can do a non-compat operation?
> 
> The only reason it's needed here is that the caller is in a kernel 
> thread rather than a system call. Are there any possible scenarios where 
> one would actually need the opposite?
> 

Quite possibly. The ext4 vs. compat getdents bug is still unresolved. 
Please see,
https://lore.kernel.org/lkml/CAFEAcA9W+JK7_TrtTnL1P2ES1knNPJX9wcUvhfLwxLq9augq1w@mail.gmail.com/

>        Arnd
> 

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-18 15:16         ` Christoph Hellwig
  2020-09-19 16:21           ` Andy Lutomirski
@ 2020-09-19 22:09           ` Al Viro
  2020-09-19 22:23             ` Andy Lutomirski
  2020-09-20 13:55             ` Arnd Bergmann
  1 sibling, 2 replies; 67+ messages in thread
From: Al Viro @ 2020-09-19 22:09 UTC (permalink / raw)
  To: Christoph Hellwig
  Cc: Andrew Morton, Jens Axboe, Arnd Bergmann, David Howells,
	linux-arm-kernel, x86, linux-kernel, linux-mips, linux-parisc,
	linuxppc-dev, linux-s390, sparclinux, linux-block, linux-scsi,
	linux-fsdevel, linux-aio, io-uring, linux-arch, linux-mm, netdev,
	keyrings, linux-security-module

On Fri, Sep 18, 2020 at 05:16:15PM +0200, Christoph Hellwig wrote:
> On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
> > Said that, why not provide a variant that would take an explicit
> > "is it compat" argument and use it there?  And have the normal
> > one pass in_compat_syscall() to that...
> 
> That would help to not introduce a regression with this series yes.
> But it wouldn't fix existing bugs when io_uring is used to access
> read or write methods that use in_compat_syscall().  One example that
> I recently ran into is drivers/scsi/sg.c.

So screw such read/write methods - don't use them with io_uring.
That, BTW, is one of the reasons I'm sceptical about burying the
decisions deep into the callchain - we don't _want_ different
data layouts on read/write depending upon the 32bit vs. 64bit
caller, let alone the pointer-chasing garbage that is /dev/sg.

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-19 21:16             ` Arnd Bergmann
  2020-09-19 21:52               ` Finn Thain
@ 2020-09-19 22:22               ` Andy Lutomirski
  2020-09-21 16:10                 ` Pavel Begunkov
  1 sibling, 1 reply; 67+ messages in thread
From: Andy Lutomirski @ 2020-09-19 22:22 UTC (permalink / raw)
  To: Arnd Bergmann
  Cc: Andy Lutomirski, Christoph Hellwig, Al Viro, Andrew Morton,
	Jens Axboe, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List


> On Sep 19, 2020, at 2:16 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> 
> On Sat, Sep 19, 2020 at 6:21 PM Andy Lutomirski <luto@kernel.org> wrote:
>>> On Fri, Sep 18, 2020 at 8:16 AM Christoph Hellwig <hch@lst.de> wrote:
>>> On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
>>>> Said that, why not provide a variant that would take an explicit
>>>> "is it compat" argument and use it there?  And have the normal
>>>> one pass in_compat_syscall() to that...
>>> 
>>> That would help to not introduce a regression with this series yes.
>>> But it wouldn't fix existing bugs when io_uring is used to access
>>> read or write methods that use in_compat_syscall().  One example that
>>> I recently ran into is drivers/scsi/sg.c.
> 
> Ah, so reading /dev/input/event* would suffer from the same issue,
> and that one would in fact be broken by your patch in the hypothetical
> case that someone tried to use io_uring to read /dev/input/event on x32...
> 
> For reference, I checked the socket timestamp handling that has a
> number of corner cases with time32/time64 formats in compat mode,
> but none of those appear to be affected by the problem.
> 
>> Aside from the potentially nasty use of per-task variables, one thing
>> I don't like about PF_FORCE_COMPAT is that it's one-way.  If we're
>> going to have a generic mechanism for this, shouldn't we allow a full
>> override of the syscall arch instead of just allowing forcing compat
>> so that a compat syscall can do a non-compat operation?
> 
> The only reason it's needed here is that the caller is in a kernel
> thread rather than a system call. Are there any possible scenarios
> where one would actually need the opposite?
> 

I can certainly imagine needing to force x32 mode from a kernel thread.

As for the other direction: what exactly are the desired bitness/arch semantics of io_uring?  Is the operation bitness chosen by the io_uring creation or by the io_uring_enter() bitness?

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-19 22:09           ` Al Viro
@ 2020-09-19 22:23             ` Andy Lutomirski
  2020-09-19 22:41               ` Al Viro
  2020-09-20 13:55             ` Arnd Bergmann
  1 sibling, 1 reply; 67+ messages in thread
From: Andy Lutomirski @ 2020-09-19 22:23 UTC (permalink / raw)
  To: Al Viro
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module


> On Sep 19, 2020, at 3:09 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> 
> On Fri, Sep 18, 2020 at 05:16:15PM +0200, Christoph Hellwig wrote:
>>> On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
>>> Said that, why not provide a variant that would take an explicit
>>> "is it compat" argument and use it there?  And have the normal
>>> one pass in_compat_syscall() to that...
>> 
>> That would help to not introduce a regression with this series yes.
>> But it wouldn't fix existing bugs when io_uring is used to access
>> read or write methods that use in_compat_syscall().  One example that
>> I recently ran into is drivers/scsi/sg.c.
> 
> So screw such read/write methods - don't use them with io_uring.
> That, BTW, is one of the reasons I'm sceptical about burying the
> decisions deep into the callchain - we don't _want_ different
> data layouts on read/write depending upon the 32bit vs. 64bit
> caller, let alone the pointer-chasing garbage that is /dev/sg.

Well, we could remove in_compat_syscall(), etc and instead have an implicit parameter in DEFINE_SYSCALL.  Then everything would have to be explicit.  This would probably be a win, although it could be quite a bit of work.

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-19 22:23             ` Andy Lutomirski
@ 2020-09-19 22:41               ` Al Viro
  2020-09-19 22:53                 ` Andy Lutomirski
  0 siblings, 1 reply; 67+ messages in thread
From: Al Viro @ 2020-09-19 22:41 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

On Sat, Sep 19, 2020 at 03:23:54PM -0700, Andy Lutomirski wrote:
> 
> > On Sep 19, 2020, at 3:09 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> > 
> > On Fri, Sep 18, 2020 at 05:16:15PM +0200, Christoph Hellwig wrote:
> >>> On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
> >>> Said that, why not provide a variant that would take an explicit
> >>> "is it compat" argument and use it there?  And have the normal
> >>> one pass in_compat_syscall() to that...
> >> 
> >> That would help to not introduce a regression with this series yes.
> >> But it wouldn't fix existing bugs when io_uring is used to access
> >> read or write methods that use in_compat_syscall().  One example that
> >> I recently ran into is drivers/scsi/sg.c.
> > 
> > So screw such read/write methods - don't use them with io_uring.
> > That, BTW, is one of the reasons I'm sceptical about burying the
> > decisions deep into the callchain - we don't _want_ different
> > data layouts on read/write depending upon the 32bit vs. 64bit
> > caller, let alone the pointer-chasing garbage that is /dev/sg.
> 
> Well, we could remove in_compat_syscall(), etc and instead have an implicit parameter in DEFINE_SYSCALL.  Then everything would have to be explicit.  This would probably be a win, although it could be quite a bit of work.

It would not be a win - most of the syscalls don't give a damn
about 32bit vs. 64bit...

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-19 22:41               ` Al Viro
@ 2020-09-19 22:53                 ` Andy Lutomirski
  2020-09-19 23:24                   ` Al Viro
  0 siblings, 1 reply; 67+ messages in thread
From: Andy Lutomirski @ 2020-09-19 22:53 UTC (permalink / raw)
  To: Al Viro
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module



> On Sep 19, 2020, at 3:41 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> 
> On Sat, Sep 19, 2020 at 03:23:54PM -0700, Andy Lutomirski wrote:
>> 
>>>> On Sep 19, 2020, at 3:09 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
>>> 
>>> On Fri, Sep 18, 2020 at 05:16:15PM +0200, Christoph Hellwig wrote:
>>>>> On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
>>>>> Said that, why not provide a variant that would take an explicit
>>>>> "is it compat" argument and use it there?  And have the normal
>>>>> one pass in_compat_syscall() to that...
>>>> 
>>>> That would help to not introduce a regression with this series yes.
>>>> But it wouldn't fix existing bugs when io_uring is used to access
>>>> read or write methods that use in_compat_syscall().  One example that
>>>> I recently ran into is drivers/scsi/sg.c.
>>> 
>>> So screw such read/write methods - don't use them with io_uring.
>>> That, BTW, is one of the reasons I'm sceptical about burying the
>>> decisions deep into the callchain - we don't _want_ different
>>> data layouts on read/write depending upon the 32bit vs. 64bit
>>> caller, let alone the pointer-chasing garbage that is /dev/sg.
>> 
>> Well, we could remove in_compat_syscall(), etc and instead have an implicit parameter in DEFINE_SYSCALL.  Then everything would have to be explicit.  This would probably be a win, although it could be quite a bit of work.
> 
> It would not be a win - most of the syscalls don't give a damn
> about 32bit vs. 64bit...

Any reasonable implementation would optimize it out for syscalls that don’t care.  Or it could be explicit:

DEFINE_MULTIARCH_SYSCALL(...)

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-19 22:53                 ` Andy Lutomirski
@ 2020-09-19 23:24                   ` Al Viro
  2020-09-20  0:14                     ` Andy Lutomirski
  0 siblings, 1 reply; 67+ messages in thread
From: Al Viro @ 2020-09-19 23:24 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

On Sat, Sep 19, 2020 at 03:53:40PM -0700, Andy Lutomirski wrote:

> > It would not be a win - most of the syscalls don't give a damn
> > about 32bit vs. 64bit...
> 
> Any reasonable implementation would optimize it out for syscalls that don’t care.  Or it could be explicit:
> 
> DEFINE_MULTIARCH_SYSCALL(...)

1) what would that look like?
2) have you counted the syscalls that do and do not need that?
3) how many of those realistically *can* be unified with their
compat counterparts?  [hint: ioctl(2) cannot]

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-19 23:24                   ` Al Viro
@ 2020-09-20  0:14                     ` Andy Lutomirski
  2020-09-20  2:57                       ` Al Viro
  0 siblings, 1 reply; 67+ messages in thread
From: Andy Lutomirski @ 2020-09-20  0:14 UTC (permalink / raw)
  To: Al Viro
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, X86 ML, LKML, open list:MIPS,
	Parisc List, linuxppc-dev, linux-s390, sparclinux, linux-block,
	Linux SCSI List, Linux FS Devel, linux-aio, io-uring, linux-arch,
	Linux-MM, Network Development, keyrings, LSM List

On Sat, Sep 19, 2020 at 4:24 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Sat, Sep 19, 2020 at 03:53:40PM -0700, Andy Lutomirski wrote:
>
> > > It would not be a win - most of the syscalls don't give a damn
> > > about 32bit vs. 64bit...
> >
> > Any reasonable implementation would optimize it out for syscalls that don’t care.  Or it could be explicit:
> >
> > DEFINE_MULTIARCH_SYSCALL(...)
>
> 1) what would that look like?

In effect, it would work like this:

/* Arch-specific, but there's a generic case for sane architectures. */
enum syscall_arch {
  SYSCALL_NATIVE,
  SYSCALL_COMPAT,
  SYSCALL_X32,
};

DEFINE_MULTIARCH_SYSCALLn(args, arch)
{
  args are the args here, and arch is the arch.
}

> 2) have you counted the syscalls that do and do not need that?

No.

> 3) how many of those realistically *can* be unified with their
> compat counterparts?  [hint: ioctl(2) cannot]

There would be no requirement to unify anything.  The idea is that
we'd get rid of all the global state flags.

For ioctl, we'd have a new file_operation:

long ioctl(struct file *, unsigned int, unsigned long, enum syscall_arch);

I'm not saying this is easy, but I think it's possible and the result
would be more obviously correct than what we have now.

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20  0:14                     ` Andy Lutomirski
@ 2020-09-20  2:57                       ` Al Viro
  2020-09-20 16:59                         ` Andy Lutomirski
  0 siblings, 1 reply; 67+ messages in thread
From: Al Viro @ 2020-09-20  2:57 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, X86 ML, LKML, open list:MIPS,
	Parisc List, linuxppc-dev, linux-s390, sparclinux, linux-block,
	Linux SCSI List, Linux FS Devel, linux-aio, io-uring, linux-arch,
	Linux-MM, Network Development, keyrings, LSM List

On Sat, Sep 19, 2020 at 05:14:41PM -0700, Andy Lutomirski wrote:

> > 2) have you counted the syscalls that do and do not need that?
> 
> No.

Might be illuminating...

> > 3) how many of those realistically *can* be unified with their
> > compat counterparts?  [hint: ioctl(2) cannot]
> 
> There would be no requirement to unify anything.  The idea is that
> we'd get rid of all the global state flags.

_What_ global state flags?  When you have separate SYSCALL_DEFINE3(ioctl...)
and COMPAT_SYSCALL_DEFINE3(ioctl...), there's no flags at all, global or
local.  They only come into the play when you try to share the same function
for both, right on the top level.

> For ioctl, we'd have a new file_operation:
> 
> long ioctl(struct file *, unsigned int, unsigned long, enum syscall_arch);
> 
> I'm not saying this is easy, but I think it's possible and the result
> would be more obviously correct than what we have now.

No, it would not.  Seriously, from time to time a bit of RTFS before grand
proposals turns out to be useful.

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-19 22:09           ` Al Viro
  2020-09-19 22:23             ` Andy Lutomirski
@ 2020-09-20 13:55             ` Arnd Bergmann
  2020-09-20 15:02               ` Al Viro
  1 sibling, 1 reply; 67+ messages in thread
From: Arnd Bergmann @ 2020-09-20 13:55 UTC (permalink / raw)
  To: Al Viro
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, David Howells,
	Linux ARM, the arch/x86 maintainers, linux-kernel,
	open list:BROADCOM NVRAM DRIVER, Parisc List, linuxppc-dev,
	linux-s390, sparclinux, linux-block, linux-scsi,
	Linux FS-devel Mailing List, linux-aio, io-uring, linux-arch,
	Linux-MM, Networking, keyrings, LSM List

On Sun, Sep 20, 2020 at 12:09 AM Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Fri, Sep 18, 2020 at 05:16:15PM +0200, Christoph Hellwig wrote:
> > On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
> > > Said that, why not provide a variant that would take an explicit
> > > "is it compat" argument and use it there?  And have the normal
> > > one pass in_compat_syscall() to that...
> >
> > That would help to not introduce a regression with this series yes.
> > But it wouldn't fix existing bugs when io_uring is used to access
> > read or write methods that use in_compat_syscall().  One example that
> > I recently ran into is drivers/scsi/sg.c.
>
> So screw such read/write methods - don't use them with io_uring.
> That, BTW, is one of the reasons I'm sceptical about burying the
> decisions deep into the callchain - we don't _want_ different
> data layouts on read/write depending upon the 32bit vs. 64bit
> caller, let alone the pointer-chasing garbage that is /dev/sg.

Would it be too late to limit what kind of file descriptors we allow
io_uring to read/write on?

If io_uring can get changed to return -EINVAL on trying to
read/write something other than S_IFREG file descriptors,
that particular problem space gets a lot simpler, but this
is of course only possible if nobody actually relies on it yet.

      Arnd

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 13:55             ` Arnd Bergmann
@ 2020-09-20 15:02               ` Al Viro
  0 siblings, 0 replies; 67+ messages in thread
From: Al Viro @ 2020-09-20 15:02 UTC (permalink / raw)
  To: Arnd Bergmann
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, David Howells,
	Linux ARM, the arch/x86 maintainers, linux-kernel,
	open list:BROADCOM NVRAM DRIVER, Parisc List, linuxppc-dev,
	linux-s390, sparclinux, linux-block, linux-scsi,
	Linux FS-devel Mailing List, linux-aio, io-uring, linux-arch,
	Linux-MM, Networking, keyrings, LSM List

On Sun, Sep 20, 2020 at 03:55:47PM +0200, Arnd Bergmann wrote:
> On Sun, Sep 20, 2020 at 12:09 AM Al Viro <viro@zeniv.linux.org.uk> wrote:
> > On Fri, Sep 18, 2020 at 05:16:15PM +0200, Christoph Hellwig wrote:
> > > On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
> > > > Said that, why not provide a variant that would take an explicit
> > > > "is it compat" argument and use it there?  And have the normal
> > > > one pass in_compat_syscall() to that...
> > >
> > > That would help to not introduce a regression with this series yes.
> > > But it wouldn't fix existing bugs when io_uring is used to access
> > > read or write methods that use in_compat_syscall().  One example that
> > > I recently ran into is drivers/scsi/sg.c.
> >
> > So screw such read/write methods - don't use them with io_uring.
> > That, BTW, is one of the reasons I'm sceptical about burying the
> > decisions deep into the callchain - we don't _want_ different
> > data layouts on read/write depending upon the 32bit vs. 64bit
> > caller, let alone the pointer-chasing garbage that is /dev/sg.
> 
> Would it be too late to limit what kind of file descriptors we allow
> io_uring to read/write on?
> 
> If io_uring can get changed to return -EINVAL on trying to
> read/write something other than S_IFREG file descriptors,
> that particular problem space gets a lot simpler, but this
> is of course only possible if nobody actually relies on it yet.

S_IFREG is almost certainly too heavy as a restriction.  Looking through
the stuff sensitive to 32bit/64bit, we seem to have
	* /dev/sg - pointer-chasing horror
	* sysfs files for efivar - different layouts for compat and native,
shitty userland ABI design (
struct efi_variable {
        efi_char16_t  VariableName[EFI_VAR_NAME_LEN/sizeof(efi_char16_t)];
        efi_guid_t    VendorGuid;
        unsigned long DataSize;
        __u8          Data[1024];
        efi_status_t  Status;
        __u32         Attributes;
} __attribute__((packed));
) is the piece of crap in question; 'DataSize' is where the headache comes
from.  Regular files, BTW...
	* uhid - character device, milder pointer-chasing horror.  Trouble
comes from this:
/* Obsolete! Use UHID_CREATE2. */
struct uhid_create_req {
        __u8 name[128];
        __u8 phys[64];
        __u8 uniq[64];
        __u8 __user *rd_data;
        __u16 rd_size;

        __u16 bus;
        __u32 vendor;
        __u32 product;
        __u32 version;
        __u32 country;
} __attribute__((__packed__));
and suggested replacement doesn't do any pointer-chasing (rd_data is an
embedded array in the end of struct uhid_create2_req).
	* evdev, uinput - bitness-sensitive layout, due to timestamps
	* /proc/bus/input/devices - weird crap with printing bitmap, different
_text_ layouts seen by 32bit and 64bit readers.  Binary structures are PITA,
but with sufficient effort you can screw the text just as hard...  Oh, and it's
a regular file.
	* similar in sysfs analogue

And AFAICS, that's it for read/write-related method instances.

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-18 12:45 ` [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag Christoph Hellwig
  2020-09-18 13:40   ` Al Viro
@ 2020-09-20 15:15   ` Matthew Wilcox
  2020-09-20 15:55     ` William Kucharski
                       ` (2 more replies)
  1 sibling, 3 replies; 67+ messages in thread
From: Matthew Wilcox @ 2020-09-20 15:15 UTC (permalink / raw)
  To: Christoph Hellwig
  Cc: Alexander Viro, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

On Fri, Sep 18, 2020 at 02:45:25PM +0200, Christoph Hellwig wrote:
> Add a flag to force processing a syscall as a compat syscall.  This is
> required so that in_compat_syscall() works for I/O submitted by io_uring
> helper threads on behalf of compat syscalls.

Al doesn't like this much, but my suggestion is to introduce two new
opcodes -- IORING_OP_READV32 and IORING_OP_WRITEV32.  The compat code
can translate IORING_OP_READV to IORING_OP_READV32 and then the core
code can know what that user pointer is pointing to.


^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 15:15   ` Matthew Wilcox
@ 2020-09-20 15:55     ` William Kucharski
  2020-09-21 16:20       ` Pavel Begunkov
  2020-09-20 16:00     ` Arnd Bergmann
  2020-09-20 18:07     ` Al Viro
  2 siblings, 1 reply; 67+ messages in thread
From: William Kucharski @ 2020-09-20 15:55 UTC (permalink / raw)
  To: Matthew Wilcox
  Cc: Christoph Hellwig, Alexander Viro, Andrew Morton, Jens Axboe,
	Arnd Bergmann, David Howells, linux-arm-kernel, x86,
	linux-kernel, linux-mips, linux-parisc, linuxppc-dev, linux-s390,
	sparclinux, linux-block, linux-scsi, linux-fsdevel, linux-aio,
	io-uring, linux-arch, linux-mm, netdev, keyrings,
	linux-security-module

I really like that as it’s self-documenting and anyone debugging it can see what is actually being used at a glance.

> On Sep 20, 2020, at 09:15, Matthew Wilcox <willy@infradead.org> wrote:
> 
> On Fri, Sep 18, 2020 at 02:45:25PM +0200, Christoph Hellwig wrote:
>> Add a flag to force processing a syscall as a compat syscall.  This is
>> required so that in_compat_syscall() works for I/O submitted by io_uring
>> helper threads on behalf of compat syscalls.
> 
> Al doesn't like this much, but my suggestion is to introduce two new
> opcodes -- IORING_OP_READV32 and IORING_OP_WRITEV32.  The compat code
> can translate IORING_OP_READV to IORING_OP_READV32 and then the core
> code can know what that user pointer is pointing to.

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 15:15   ` Matthew Wilcox
  2020-09-20 15:55     ` William Kucharski
@ 2020-09-20 16:00     ` Arnd Bergmann
  2020-09-20 18:07     ` Al Viro
  2 siblings, 0 replies; 67+ messages in thread
From: Arnd Bergmann @ 2020-09-20 16:00 UTC (permalink / raw)
  To: Matthew Wilcox
  Cc: Christoph Hellwig, Alexander Viro, Andrew Morton, Jens Axboe,
	David Howells, Linux ARM, the arch/x86 maintainers, linux-kernel,
	open list:BROADCOM NVRAM DRIVER, Parisc List, linuxppc-dev,
	linux-s390, sparclinux, linux-block, linux-scsi,
	Linux FS-devel Mailing List, linux-aio, io-uring, linux-arch,
	Linux-MM, Networking, keyrings, LSM List

On Sun, Sep 20, 2020 at 5:15 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Fri, Sep 18, 2020 at 02:45:25PM +0200, Christoph Hellwig wrote:
> > Add a flag to force processing a syscall as a compat syscall.  This is
> > required so that in_compat_syscall() works for I/O submitted by io_uring
> > helper threads on behalf of compat syscalls.
>
> Al doesn't like this much, but my suggestion is to introduce two new
> opcodes -- IORING_OP_READV32 and IORING_OP_WRITEV32.  The compat code
> can translate IORING_OP_READV to IORING_OP_READV32 and then the core
> code can know what that user pointer is pointing to.

How is that different from the current approach of storing the ABI as
a flag in ctx->compat?

     Arnd

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20  2:57                       ` Al Viro
@ 2020-09-20 16:59                         ` Andy Lutomirski
  2020-09-20 18:12                           ` Al Viro
  0 siblings, 1 reply; 67+ messages in thread
From: Andy Lutomirski @ 2020-09-20 16:59 UTC (permalink / raw)
  To: Al Viro
  Cc: Andy Lutomirski, Christoph Hellwig, Andrew Morton, Jens Axboe,
	Arnd Bergmann, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List

On Sat, Sep 19, 2020 at 7:57 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Sat, Sep 19, 2020 at 05:14:41PM -0700, Andy Lutomirski wrote:
>
> > > 2) have you counted the syscalls that do and do not need that?
> >
> > No.
>
> Might be illuminating...
>
> > > 3) how many of those realistically *can* be unified with their
> > > compat counterparts?  [hint: ioctl(2) cannot]
> >
> > There would be no requirement to unify anything.  The idea is that
> > we'd get rid of all the global state flags.
>
> _What_ global state flags?  When you have separate SYSCALL_DEFINE3(ioctl...)
> and COMPAT_SYSCALL_DEFINE3(ioctl...), there's no flags at all, global or
> local.  They only come into the play when you try to share the same function
> for both, right on the top level.

...

>
> > For ioctl, we'd have a new file_operation:
> >
> > long ioctl(struct file *, unsigned int, unsigned long, enum syscall_arch);
> >
> > I'm not saying this is easy, but I think it's possible and the result
> > would be more obviously correct than what we have now.
>
> No, it would not.  Seriously, from time to time a bit of RTFS before grand
> proposals turns out to be useful.

As one example, look at __sys_setsockopt().  It's called for the
native and compat versions, and it contains an in_compat_syscall()
check.  (This particularly check looks dubious to me, but that's
another story.)  If this were to be done with equivalent semantics
without a separate COMPAT_DEFINE_SYSCALL and without
in_compat_syscall(), there would need to be some indication as to
whether this is compat or native setsockopt.  There are other
setsockopt implementations in the net stack with more
legitimate-seeming uses of in_compat_syscall() that would need some
other mechanism if in_compat_syscall() were to go away.

setsockopt is (I hope!) out of scope for io_uring, but the situation
isn't fundamentally different from read and write.

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 15:15   ` Matthew Wilcox
  2020-09-20 15:55     ` William Kucharski
  2020-09-20 16:00     ` Arnd Bergmann
@ 2020-09-20 18:07     ` Al Viro
  2020-09-20 18:41       ` Al Viro
                         ` (2 more replies)
  2 siblings, 3 replies; 67+ messages in thread
From: Al Viro @ 2020-09-20 18:07 UTC (permalink / raw)
  To: Matthew Wilcox
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

On Sun, Sep 20, 2020 at 04:15:10PM +0100, Matthew Wilcox wrote:
> On Fri, Sep 18, 2020 at 02:45:25PM +0200, Christoph Hellwig wrote:
> > Add a flag to force processing a syscall as a compat syscall.  This is
> > required so that in_compat_syscall() works for I/O submitted by io_uring
> > helper threads on behalf of compat syscalls.
> 
> Al doesn't like this much, but my suggestion is to introduce two new
> opcodes -- IORING_OP_READV32 and IORING_OP_WRITEV32.  The compat code
> can translate IORING_OP_READV to IORING_OP_READV32 and then the core
> code can know what that user pointer is pointing to.

Let's separate two issues:
	1) compat syscalls want 32bit iovecs.  Nothing to do with the
drivers, dealt with just fine.
	2) a few drivers are really fucked in head.  They use different
*DATA* layouts for reads/writes, depending upon the calling process.
IOW, if you fork/exec a 32bit binary and your stdin is one of those,
reads from stdin in parent and child will yield different data layouts.
On the same struct file.
	That's what Christoph worries about (/dev/sg he'd mentioned is
one of those).

	IMO we should simply have that dozen or so of pathological files
marked with FMODE_SHITTY_ABI; it's not about how they'd been opened -
it describes the userland ABI provided by those.  And it's cast in stone.

	Any in_compat_syscall() in ->read()/->write() instances is an ABI
bug, plain and simple.  Some are unfixable for compatibility reasons, but
any new caller like that should be a big red flag.

	How we import iovec array is none of the drivers' concern; we do
not need to mess with in_compat_syscall() reporting the matching value,
etc. for that.  It's about the instances that want in_compat_syscall() to
decide between the 32bit and 64bit data layouts.  And I believe that
we should simply have them marked as such and rejected by io_uring.  With
any new occurences getting slapped down hard.

	Current list of those turds:
/dev/sg (pointer-chasing, generally insane)
/sys/firmware/efi/vars/*/raw_var (fucked binary structure)
/sys/firmware/efi/vars/new_var (fucked binary structure)
/sys/firmware/efi/vars/del_var (fucked binary structure)
/dev/uhid	(pointer-chasing for one obsolete command)
/dev/input/event* (timestamps)
/dev/uinput (timestamps)
/proc/bus/input/devices (fucked bitmap-to-text representation)
/sys/class/input/*/capabilities/* (fucked bitmap-to-text representation)

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 16:59                         ` Andy Lutomirski
@ 2020-09-20 18:12                           ` Al Viro
  0 siblings, 0 replies; 67+ messages in thread
From: Al Viro @ 2020-09-20 18:12 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, X86 ML, LKML, open list:MIPS,
	Parisc List, linuxppc-dev, linux-s390, sparclinux, linux-block,
	Linux SCSI List, Linux FS Devel, linux-aio, io-uring, linux-arch,
	Linux-MM, Network Development, keyrings, LSM List

On Sun, Sep 20, 2020 at 09:59:36AM -0700, Andy Lutomirski wrote:

> As one example, look at __sys_setsockopt().  It's called for the
> native and compat versions, and it contains an in_compat_syscall()
> check.  (This particularly check looks dubious to me, but that's
> another story.)  If this were to be done with equivalent semantics
> without a separate COMPAT_DEFINE_SYSCALL and without
> in_compat_syscall(), there would need to be some indication as to
> whether this is compat or native setsockopt.  There are other
> setsockopt implementations in the net stack with more
> legitimate-seeming uses of in_compat_syscall() that would need some
> other mechanism if in_compat_syscall() were to go away.
> 
> setsockopt is (I hope!) out of scope for io_uring, but the situation
> isn't fundamentally different from read and write.

	Except that setsockopt() had that crap very widespread; for read()
and write() those are very rare exceptions.

	Andy, please RTFS.  Or dig through archives.  The situation
with setsockopt() is *NOT* a good thing - it's (probably) the least
of the evils.  The last thing we need is making that the norm.

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 18:07     ` Al Viro
@ 2020-09-20 18:41       ` Al Viro
  2020-09-20 19:01       ` Matthew Wilcox
  2020-09-20 19:14       ` Andy Lutomirski
  2 siblings, 0 replies; 67+ messages in thread
From: Al Viro @ 2020-09-20 18:41 UTC (permalink / raw)
  To: Matthew Wilcox
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

On Sun, Sep 20, 2020 at 07:07:42PM +0100, Al Viro wrote:

> /proc/bus/input/devices (fucked bitmap-to-text representation)

To illustrate the, er, beauty of that stuff:

; cat32 /proc/bus/input/devices >/tmp/a
; cat /proc/bus/input/devices >/tmp/b
; diff -u /tmp/a /tmp/b|grep '^[-+]'
--- /tmp/a      2020-09-20 14:28:43.442560691 -0400
+++ /tmp/b      2020-09-20 14:28:49.018543230 -0400
-B: KEY=1100f 2902000 8380307c f910f001 feffffdf ffefffff ffffffff fffffffe
+B: KEY=1100f02902000 8380307cf910f001 feffffdfffefffff fffffffffffffffe
-B: KEY=70000 0 0 0 0 0 0 0 0
+B: KEY=70000 0 0 0 0
-B: KEY=420 0 70000 0 0 0 0 0 0 0 0
+B: KEY=420 70000 0 0 0 0
-B: KEY=100000 0 0 0
+B: KEY=10000000000000 0
-B: KEY=4000 0 0 0 0
+B: KEY=4000 0 0
-B: KEY=8000 0 0 0 0 0 1100b 800 2 200000 0 0 0 0
+B: KEY=800000000000 0 0 1100b00000800 200200000 0 0
-B: KEY=3e000b 0 0 0 0 0 0 0
+B: KEY=3e000b00000000 0 0 0
-B: KEY=ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff fffffffe
+B: KEY=ffffffffffffffff ffffffffffffffff ffffffffffffffff fffffffffffffffe
; 
(cat32 being a 32bit binary of cat)
All the differences are due to homegrown bitmap-to-text conversion.

Note that feeding that into a pipe leaves the recepient with a lovely problem -
you can't go by the width of words (they are not zero-padded) and you can't
go by the number of words either - it varies from device to device.

And there's nothing we can do with that - it's a userland ABI, can't be
changed without breaking stuff.  I would prefer to avoid additional examples
like that, TYVM...

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 18:07     ` Al Viro
  2020-09-20 18:41       ` Al Viro
@ 2020-09-20 19:01       ` Matthew Wilcox
  2020-09-20 19:10         ` Al Viro
  2020-09-20 19:14       ` Andy Lutomirski
  2 siblings, 1 reply; 67+ messages in thread
From: Matthew Wilcox @ 2020-09-20 19:01 UTC (permalink / raw)
  To: Al Viro
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

On Sun, Sep 20, 2020 at 07:07:42PM +0100, Al Viro wrote:
> 	2) a few drivers are really fucked in head.  They use different
> *DATA* layouts for reads/writes, depending upon the calling process.
> IOW, if you fork/exec a 32bit binary and your stdin is one of those,
> reads from stdin in parent and child will yield different data layouts.
> On the same struct file.
> 	That's what Christoph worries about (/dev/sg he'd mentioned is
> one of those).
> 
> 	IMO we should simply have that dozen or so of pathological files
> marked with FMODE_SHITTY_ABI; it's not about how they'd been opened -
> it describes the userland ABI provided by those.  And it's cast in stone.
> 
> 	Any in_compat_syscall() in ->read()/->write() instances is an ABI
> bug, plain and simple.  Some are unfixable for compatibility reasons, but
> any new caller like that should be a big red flag.

So an IOCB_COMPAT flag would let us know whether the caller is expecting
a 32-bit or 64-bit layout?  And io_uring could set it based on the
ctx->compat flag.

> 	Current list of those turds:
> /dev/sg (pointer-chasing, generally insane)
> /sys/firmware/efi/vars/*/raw_var (fucked binary structure)
> /sys/firmware/efi/vars/new_var (fucked binary structure)
> /sys/firmware/efi/vars/del_var (fucked binary structure)
> /dev/uhid	(pointer-chasing for one obsolete command)
> /dev/input/event* (timestamps)
> /dev/uinput (timestamps)
> /proc/bus/input/devices (fucked bitmap-to-text representation)
> /sys/class/input/*/capabilities/* (fucked bitmap-to-text representation)

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 19:01       ` Matthew Wilcox
@ 2020-09-20 19:10         ` Al Viro
  2020-09-20 19:22           ` Matthew Wilcox
  0 siblings, 1 reply; 67+ messages in thread
From: Al Viro @ 2020-09-20 19:10 UTC (permalink / raw)
  To: Matthew Wilcox
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

On Sun, Sep 20, 2020 at 08:01:59PM +0100, Matthew Wilcox wrote:
> On Sun, Sep 20, 2020 at 07:07:42PM +0100, Al Viro wrote:
> > 	2) a few drivers are really fucked in head.  They use different
> > *DATA* layouts for reads/writes, depending upon the calling process.
> > IOW, if you fork/exec a 32bit binary and your stdin is one of those,
> > reads from stdin in parent and child will yield different data layouts.
> > On the same struct file.
> > 	That's what Christoph worries about (/dev/sg he'd mentioned is
> > one of those).
> > 
> > 	IMO we should simply have that dozen or so of pathological files
> > marked with FMODE_SHITTY_ABI; it's not about how they'd been opened -
> > it describes the userland ABI provided by those.  And it's cast in stone.
> > 
> > 	Any in_compat_syscall() in ->read()/->write() instances is an ABI
> > bug, plain and simple.  Some are unfixable for compatibility reasons, but
> > any new caller like that should be a big red flag.
> 
> So an IOCB_COMPAT flag would let us know whether the caller is expecting
> a 32-bit or 64-bit layout?  And io_uring could set it based on the
> ctx->compat flag.

So you want to convert all that crap to a form that would see iocb
(IOW, ->read_iter()/->write_iter())?  And, since quite a few are sysfs
attributes, propagate that through sysfs, changing the method signatures
to match that and either modifying fuckloads of instances or introducing
new special methods for the ones that are sensitive to that crap?

IMO it's much saner to mark those and refuse to touch them from io_uring...

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 18:07     ` Al Viro
  2020-09-20 18:41       ` Al Viro
  2020-09-20 19:01       ` Matthew Wilcox
@ 2020-09-20 19:14       ` Andy Lutomirski
  2020-09-21  4:28         ` Christoph Hellwig
  2 siblings, 1 reply; 67+ messages in thread
From: Andy Lutomirski @ 2020-09-20 19:14 UTC (permalink / raw)
  To: Al Viro
  Cc: Matthew Wilcox, Christoph Hellwig, Andrew Morton, Jens Axboe,
	Arnd Bergmann, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List

On Sun, Sep 20, 2020 at 11:07 AM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Sun, Sep 20, 2020 at 04:15:10PM +0100, Matthew Wilcox wrote:
> > On Fri, Sep 18, 2020 at 02:45:25PM +0200, Christoph Hellwig wrote:
> > > Add a flag to force processing a syscall as a compat syscall.  This is
> > > required so that in_compat_syscall() works for I/O submitted by io_uring
> > > helper threads on behalf of compat syscalls.
> >
> > Al doesn't like this much, but my suggestion is to introduce two new
> > opcodes -- IORING_OP_READV32 and IORING_OP_WRITEV32.  The compat code
> > can translate IORING_OP_READV to IORING_OP_READV32 and then the core
> > code can know what that user pointer is pointing to.
>
> Let's separate two issues:
>         1) compat syscalls want 32bit iovecs.  Nothing to do with the
> drivers, dealt with just fine.
>         2) a few drivers are really fucked in head.  They use different
> *DATA* layouts for reads/writes, depending upon the calling process.
> IOW, if you fork/exec a 32bit binary and your stdin is one of those,
> reads from stdin in parent and child will yield different data layouts.
> On the same struct file.
>         That's what Christoph worries about (/dev/sg he'd mentioned is
> one of those).
>
>         IMO we should simply have that dozen or so of pathological files
> marked with FMODE_SHITTY_ABI; it's not about how they'd been opened -
> it describes the userland ABI provided by those.  And it's cast in stone.
>

I wonder if this is really quite cast in stone.  We could also have
FMODE_SHITTY_COMPAT and set that when a file like this is *opened* in
compat mode.  Then that particular struct file would be read and
written using the compat data format.  The change would be
user-visible, but the user that would see it would be very strange
indeed.

I don't have a strong opinion as to whether that is better or worse
than denying io_uring access to these things, but at least it moves
the special case out of io_uring.

--Andy

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 19:10         ` Al Viro
@ 2020-09-20 19:22           ` Matthew Wilcox
  2020-09-20 19:28             ` Andy Lutomirski
                               ` (2 more replies)
  0 siblings, 3 replies; 67+ messages in thread
From: Matthew Wilcox @ 2020-09-20 19:22 UTC (permalink / raw)
  To: Al Viro
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

On Sun, Sep 20, 2020 at 08:10:31PM +0100, Al Viro wrote:
> IMO it's much saner to mark those and refuse to touch them from io_uring...

Simpler solution is to remove io_uring from the 32-bit syscall list.
If you're a 32-bit process, you don't get to use io_uring.  Would
any real users actually care about that?

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 19:22           ` Matthew Wilcox
@ 2020-09-20 19:28             ` Andy Lutomirski
  2020-09-20 20:49               ` Arnd Bergmann
  2020-09-20 21:42             ` Al Viro
  2020-09-21 16:26             ` Pavel Begunkov
  2 siblings, 1 reply; 67+ messages in thread
From: Andy Lutomirski @ 2020-09-20 19:28 UTC (permalink / raw)
  To: Matthew Wilcox
  Cc: Al Viro, Christoph Hellwig, Andrew Morton, Jens Axboe,
	Arnd Bergmann, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List

On Sun, Sep 20, 2020 at 12:23 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Sun, Sep 20, 2020 at 08:10:31PM +0100, Al Viro wrote:
> > IMO it's much saner to mark those and refuse to touch them from io_uring...
>
> Simpler solution is to remove io_uring from the 32-bit syscall list.
> If you're a 32-bit process, you don't get to use io_uring.  Would
> any real users actually care about that?

We could go one step farther and declare that we're done adding *any*
new compat syscalls :)



-- 
Andy Lutomirski
AMA Capital Management, LLC

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 19:28             ` Andy Lutomirski
@ 2020-09-20 20:49               ` Arnd Bergmann
  2020-09-20 21:13                 ` David Laight
  0 siblings, 1 reply; 67+ messages in thread
From: Arnd Bergmann @ 2020-09-20 20:49 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: Matthew Wilcox, Al Viro, Christoph Hellwig, Andrew Morton,
	Jens Axboe, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List

On Sun, Sep 20, 2020 at 9:28 PM Andy Lutomirski <luto@kernel.org> wrote:
> On Sun, Sep 20, 2020 at 12:23 PM Matthew Wilcox <willy@infradead.org> wrote:
> >
> > On Sun, Sep 20, 2020 at 08:10:31PM +0100, Al Viro wrote:
> > > IMO it's much saner to mark those and refuse to touch them from io_uring...
> >
> > Simpler solution is to remove io_uring from the 32-bit syscall list.
> > If you're a 32-bit process, you don't get to use io_uring.  Would
> > any real users actually care about that?
>
> We could go one step farther and declare that we're done adding *any*
> new compat syscalls :)

Would you also stop adding system calls to native 32-bit systems then?

On memory constrained systems (less than 2GB a.t.m.), there is still a
strong demand for running 32-bit user space, but all of the recent Arm
cores (after Cortex-A55) dropped the ability to run 32-bit kernels, so
that compat mode may eventually become the primary way to run
Linux on cheap embedded systems.

I don't think there is any chance we can realistically take away io_uring
from the 32-bit ABI any more now.

      Arnd

^ permalink raw reply	[flat|nested] 67+ messages in thread

* RE: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 20:49               ` Arnd Bergmann
@ 2020-09-20 21:13                 ` David Laight
  2020-09-21 16:31                   ` Pavel Begunkov
  0 siblings, 1 reply; 67+ messages in thread
From: David Laight @ 2020-09-20 21:13 UTC (permalink / raw)
  To: 'Arnd Bergmann', Andy Lutomirski
  Cc: Matthew Wilcox, Al Viro, Christoph Hellwig, Andrew Morton,
	Jens Axboe, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List

From: Arnd Bergmann
> Sent: 20 September 2020 21:49
> 
> On Sun, Sep 20, 2020 at 9:28 PM Andy Lutomirski <luto@kernel.org> wrote:
> > On Sun, Sep 20, 2020 at 12:23 PM Matthew Wilcox <willy@infradead.org> wrote:
> > >
> > > On Sun, Sep 20, 2020 at 08:10:31PM +0100, Al Viro wrote:
> > > > IMO it's much saner to mark those and refuse to touch them from io_uring...
> > >
> > > Simpler solution is to remove io_uring from the 32-bit syscall list.
> > > If you're a 32-bit process, you don't get to use io_uring.  Would
> > > any real users actually care about that?
> >
> > We could go one step farther and declare that we're done adding *any*
> > new compat syscalls :)
> 
> Would you also stop adding system calls to native 32-bit systems then?
> 
> On memory constrained systems (less than 2GB a.t.m.), there is still a
> strong demand for running 32-bit user space, but all of the recent Arm
> cores (after Cortex-A55) dropped the ability to run 32-bit kernels, so
> that compat mode may eventually become the primary way to run
> Linux on cheap embedded systems.
> 
> I don't think there is any chance we can realistically take away io_uring
> from the 32-bit ABI any more now.

Can't it just run requests from 32bit apps in a kernel thread that has
the 'in_compat_syscall' flag set?
Not that i recall seeing the code where it saves the 'compat' nature
of any requests.

It is already completely f*cked if you try to pass the command ring
to a child process - it uses the wrong 'mm'.
I suspect there are some really horrid security holes in that area.

	David.

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 19:22           ` Matthew Wilcox
  2020-09-20 19:28             ` Andy Lutomirski
@ 2020-09-20 21:42             ` Al Viro
  2020-09-21 16:26             ` Pavel Begunkov
  2 siblings, 0 replies; 67+ messages in thread
From: Al Viro @ 2020-09-20 21:42 UTC (permalink / raw)
  To: Matthew Wilcox
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

On Sun, Sep 20, 2020 at 08:22:59PM +0100, Matthew Wilcox wrote:
> On Sun, Sep 20, 2020 at 08:10:31PM +0100, Al Viro wrote:
> > IMO it's much saner to mark those and refuse to touch them from io_uring...
> 
> Simpler solution is to remove io_uring from the 32-bit syscall list.
> If you're a 32-bit process, you don't get to use io_uring.  Would
> any real users actually care about that?

What for?  I mean, is there any reason to try and keep those bugs as
first-class citizens?  IDGI...  Yes, we have several special files
(out of thousands) that have read()/write() user-visible semantics
broken wrt 32bit/64bit.  And we have to keep them working that way
for existing syscalls.  Why would we want to pretend that their
behaviour is normal and isn't an ABI bug, not to be repeated for
anything new?

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 19:14       ` Andy Lutomirski
@ 2020-09-21  4:28         ` Christoph Hellwig
  0 siblings, 0 replies; 67+ messages in thread
From: Christoph Hellwig @ 2020-09-21  4:28 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: Al Viro, Matthew Wilcox, Christoph Hellwig, Andrew Morton,
	Jens Axboe, Arnd Bergmann, David Howells, linux-arm-kernel,
	X86 ML, LKML, open list:MIPS, Parisc List, linuxppc-dev,
	linux-s390, sparclinux, linux-block, Linux SCSI List,
	Linux FS Devel, linux-aio, io-uring, linux-arch, Linux-MM,
	Network Development, keyrings, LSM List

On Sun, Sep 20, 2020 at 12:14:49PM -0700, Andy Lutomirski wrote:
> I wonder if this is really quite cast in stone.  We could also have
> FMODE_SHITTY_COMPAT and set that when a file like this is *opened* in
> compat mode.  Then that particular struct file would be read and
> written using the compat data format.  The change would be
> user-visible, but the user that would see it would be very strange
> indeed.
> 
> I don't have a strong opinion as to whether that is better or worse
> than denying io_uring access to these things, but at least it moves
> the special case out of io_uring.

open could have happened through an io_uring thread a well, so I don't
see how this would do anything but move the problem to a different
place.

> 
> --Andy
---end quoted text---

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: let import_iovec deal with compat_iovecs as well
  2020-09-19 14:24 ` let import_iovec deal with compat_iovecs as well David Laight
@ 2020-09-21  4:41   ` 'Christoph Hellwig'
  2020-09-21 11:11     ` David Laight
  0 siblings, 1 reply; 67+ messages in thread
From: 'Christoph Hellwig' @ 2020-09-21  4:41 UTC (permalink / raw)
  To: David Laight
  Cc: 'Christoph Hellwig',
	Alexander Viro, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

On Sat, Sep 19, 2020 at 02:24:10PM +0000, David Laight wrote:
> I thought about that change while writing my import_iovec() => iovec_import()
> patch - and thought that the io_uring code would (as usual) cause grief.
> 
> Christoph - did you see those patches?

No.

^ permalink raw reply	[flat|nested] 67+ messages in thread

* RE: let import_iovec deal with compat_iovecs as well
  2020-09-21  4:41   ` 'Christoph Hellwig'
@ 2020-09-21 11:11     ` David Laight
  0 siblings, 0 replies; 67+ messages in thread
From: David Laight @ 2020-09-21 11:11 UTC (permalink / raw)
  To: 'Christoph Hellwig'
  Cc: Alexander Viro, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

> On Sat, Sep 19, 2020 at 02:24:10PM +0000, David Laight wrote:
> > I thought about that change while writing my import_iovec() => iovec_import()
> > patch - and thought that the io_uring code would (as usual) cause grief.
> >
> > Christoph - did you see those patches?

Link to cover email.

https://lkml.org/lkml/2020/9/15/661

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)


^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-19 22:22               ` Andy Lutomirski
@ 2020-09-21 16:10                 ` Pavel Begunkov
  2020-09-21 16:13                   ` Pavel Begunkov
  0 siblings, 1 reply; 67+ messages in thread
From: Pavel Begunkov @ 2020-09-21 16:10 UTC (permalink / raw)
  To: Andy Lutomirski, Arnd Bergmann
  Cc: Andy Lutomirski, Christoph Hellwig, Al Viro, Andrew Morton,
	Jens Axboe, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List

On 20/09/2020 01:22, Andy Lutomirski wrote:
> 
>> On Sep 19, 2020, at 2:16 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>>
>> On Sat, Sep 19, 2020 at 6:21 PM Andy Lutomirski <luto@kernel.org> wrote:
>>>> On Fri, Sep 18, 2020 at 8:16 AM Christoph Hellwig <hch@lst.de> wrote:
>>>> On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
>>>>> Said that, why not provide a variant that would take an explicit
>>>>> "is it compat" argument and use it there?  And have the normal
>>>>> one pass in_compat_syscall() to that...
>>>>
>>>> That would help to not introduce a regression with this series yes.
>>>> But it wouldn't fix existing bugs when io_uring is used to access
>>>> read or write methods that use in_compat_syscall().  One example that
>>>> I recently ran into is drivers/scsi/sg.c.
>>
>> Ah, so reading /dev/input/event* would suffer from the same issue,
>> and that one would in fact be broken by your patch in the hypothetical
>> case that someone tried to use io_uring to read /dev/input/event on x32...
>>
>> For reference, I checked the socket timestamp handling that has a
>> number of corner cases with time32/time64 formats in compat mode,
>> but none of those appear to be affected by the problem.
>>
>>> Aside from the potentially nasty use of per-task variables, one thing
>>> I don't like about PF_FORCE_COMPAT is that it's one-way.  If we're
>>> going to have a generic mechanism for this, shouldn't we allow a full
>>> override of the syscall arch instead of just allowing forcing compat
>>> so that a compat syscall can do a non-compat operation?
>>
>> The only reason it's needed here is that the caller is in a kernel
>> thread rather than a system call. Are there any possible scenarios
>> where one would actually need the opposite?
>>
> 
> I can certainly imagine needing to force x32 mode from a kernel thread.
> 
> As for the other direction: what exactly are the desired bitness/arch semantics of io_uring?  Is the operation bitness chosen by the io_uring creation or by the io_uring_enter() bitness?

It's rather the second one. Even though AFAIR it wasn't discussed
specifically, that how it works now (_partially_).

-- 
Pavel Begunkov

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-21 16:10                 ` Pavel Begunkov
@ 2020-09-21 16:13                   ` Pavel Begunkov
  2020-09-21 23:51                     ` Andy Lutomirski
  0 siblings, 1 reply; 67+ messages in thread
From: Pavel Begunkov @ 2020-09-21 16:13 UTC (permalink / raw)
  To: Andy Lutomirski, Arnd Bergmann
  Cc: Andy Lutomirski, Christoph Hellwig, Al Viro, Andrew Morton,
	Jens Axboe, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List

On 21/09/2020 19:10, Pavel Begunkov wrote:
> On 20/09/2020 01:22, Andy Lutomirski wrote:
>>
>>> On Sep 19, 2020, at 2:16 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>>>
>>> On Sat, Sep 19, 2020 at 6:21 PM Andy Lutomirski <luto@kernel.org> wrote:
>>>>> On Fri, Sep 18, 2020 at 8:16 AM Christoph Hellwig <hch@lst.de> wrote:
>>>>> On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
>>>>>> Said that, why not provide a variant that would take an explicit
>>>>>> "is it compat" argument and use it there?  And have the normal
>>>>>> one pass in_compat_syscall() to that...
>>>>>
>>>>> That would help to not introduce a regression with this series yes.
>>>>> But it wouldn't fix existing bugs when io_uring is used to access
>>>>> read or write methods that use in_compat_syscall().  One example that
>>>>> I recently ran into is drivers/scsi/sg.c.
>>>
>>> Ah, so reading /dev/input/event* would suffer from the same issue,
>>> and that one would in fact be broken by your patch in the hypothetical
>>> case that someone tried to use io_uring to read /dev/input/event on x32...
>>>
>>> For reference, I checked the socket timestamp handling that has a
>>> number of corner cases with time32/time64 formats in compat mode,
>>> but none of those appear to be affected by the problem.
>>>
>>>> Aside from the potentially nasty use of per-task variables, one thing
>>>> I don't like about PF_FORCE_COMPAT is that it's one-way.  If we're
>>>> going to have a generic mechanism for this, shouldn't we allow a full
>>>> override of the syscall arch instead of just allowing forcing compat
>>>> so that a compat syscall can do a non-compat operation?
>>>
>>> The only reason it's needed here is that the caller is in a kernel
>>> thread rather than a system call. Are there any possible scenarios
>>> where one would actually need the opposite?
>>>
>>
>> I can certainly imagine needing to force x32 mode from a kernel thread.
>>
>> As for the other direction: what exactly are the desired bitness/arch semantics of io_uring?  Is the operation bitness chosen by the io_uring creation or by the io_uring_enter() bitness?
> 
> It's rather the second one. Even though AFAIR it wasn't discussed
> specifically, that how it works now (_partially_).

Double checked -- I'm wrong, that's the former one. Most of it is based
on a flag that was set an creation.

-- 
Pavel Begunkov

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 15:55     ` William Kucharski
@ 2020-09-21 16:20       ` Pavel Begunkov
  0 siblings, 0 replies; 67+ messages in thread
From: Pavel Begunkov @ 2020-09-21 16:20 UTC (permalink / raw)
  To: William Kucharski, Matthew Wilcox
  Cc: Christoph Hellwig, Alexander Viro, Andrew Morton, Jens Axboe,
	Arnd Bergmann, David Howells, linux-arm-kernel, x86,
	linux-kernel, linux-mips, linux-parisc, linuxppc-dev, linux-s390,
	sparclinux, linux-block, linux-scsi, linux-fsdevel, linux-aio,
	io-uring, linux-arch, linux-mm, netdev, keyrings,
	linux-security-module

On 20/09/2020 18:55, William Kucharski wrote:
> I really like that as it’s self-documenting and anyone debugging it can see what is actually being used at a glance.

Also creates special cases for things that few people care about,
and makes it a pain for cross-platform (cross-bitness) development.

> 
>> On Sep 20, 2020, at 09:15, Matthew Wilcox <willy@infradead.org> wrote:
>>
>> On Fri, Sep 18, 2020 at 02:45:25PM +0200, Christoph Hellwig wrote:
>>> Add a flag to force processing a syscall as a compat syscall.  This is
>>> required so that in_compat_syscall() works for I/O submitted by io_uring
>>> helper threads on behalf of compat syscalls.
>>
>> Al doesn't like this much, but my suggestion is to introduce two new
>> opcodes -- IORING_OP_READV32 and IORING_OP_WRITEV32.  The compat code
>> can translate IORING_OP_READV to IORING_OP_READV32 and then the core
>> code can know what that user pointer is pointing to.

-- 
Pavel Begunkov

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 19:22           ` Matthew Wilcox
  2020-09-20 19:28             ` Andy Lutomirski
  2020-09-20 21:42             ` Al Viro
@ 2020-09-21 16:26             ` Pavel Begunkov
  2 siblings, 0 replies; 67+ messages in thread
From: Pavel Begunkov @ 2020-09-21 16:26 UTC (permalink / raw)
  To: Matthew Wilcox, Al Viro
  Cc: Christoph Hellwig, Andrew Morton, Jens Axboe, Arnd Bergmann,
	David Howells, linux-arm-kernel, x86, linux-kernel, linux-mips,
	linux-parisc, linuxppc-dev, linux-s390, sparclinux, linux-block,
	linux-scsi, linux-fsdevel, linux-aio, io-uring, linux-arch,
	linux-mm, netdev, keyrings, linux-security-module

On 20/09/2020 22:22, Matthew Wilcox wrote:
> On Sun, Sep 20, 2020 at 08:10:31PM +0100, Al Viro wrote:
>> IMO it's much saner to mark those and refuse to touch them from io_uring...
> 
> Simpler solution is to remove io_uring from the 32-bit syscall list.
> If you're a 32-bit process, you don't get to use io_uring.  Would
> any real users actually care about that?

There were .net and\or wine (which AFAIK often works in compat) guys
experimenting with io_uring, they might want it.

-- 
Pavel Begunkov

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-20 21:13                 ` David Laight
@ 2020-09-21 16:31                   ` Pavel Begunkov
  0 siblings, 0 replies; 67+ messages in thread
From: Pavel Begunkov @ 2020-09-21 16:31 UTC (permalink / raw)
  To: David Laight, 'Arnd Bergmann', Andy Lutomirski
  Cc: Matthew Wilcox, Al Viro, Christoph Hellwig, Andrew Morton,
	Jens Axboe, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List

On 21/09/2020 00:13, David Laight wrote:
> From: Arnd Bergmann
>> Sent: 20 September 2020 21:49
>>
>> On Sun, Sep 20, 2020 at 9:28 PM Andy Lutomirski <luto@kernel.org> wrote:
>>> On Sun, Sep 20, 2020 at 12:23 PM Matthew Wilcox <willy@infradead.org> wrote:
>>>>
>>>> On Sun, Sep 20, 2020 at 08:10:31PM +0100, Al Viro wrote:
>>>>> IMO it's much saner to mark those and refuse to touch them from io_uring...
>>>>
>>>> Simpler solution is to remove io_uring from the 32-bit syscall list.
>>>> If you're a 32-bit process, you don't get to use io_uring.  Would
>>>> any real users actually care about that?
>>>
>>> We could go one step farther and declare that we're done adding *any*
>>> new compat syscalls :)
>>
>> Would you also stop adding system calls to native 32-bit systems then?
>>
>> On memory constrained systems (less than 2GB a.t.m.), there is still a
>> strong demand for running 32-bit user space, but all of the recent Arm
>> cores (after Cortex-A55) dropped the ability to run 32-bit kernels, so
>> that compat mode may eventually become the primary way to run
>> Linux on cheap embedded systems.
>>
>> I don't think there is any chance we can realistically take away io_uring
>> from the 32-bit ABI any more now.
> 
> Can't it just run requests from 32bit apps in a kernel thread that has
> the 'in_compat_syscall' flag set?
> Not that i recall seeing the code where it saves the 'compat' nature
> of any requests.
> 
> It is already completely f*cked if you try to pass the command ring
> to a child process - it uses the wrong 'mm'.

And how so? io_uring uses mm of a submitter. The exception is SQPOLL
mode, but it requires CAP_SYS_ADMIN or CAP_SYS_NICE anyway.

> I suspect there are some really horrid security holes in that area.
> 
> 	David.
> 
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
> 

-- 
Pavel Begunkov

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-21 16:13                   ` Pavel Begunkov
@ 2020-09-21 23:51                     ` Andy Lutomirski
  2020-09-22  0:22                       ` Pavel Begunkov
  0 siblings, 1 reply; 67+ messages in thread
From: Andy Lutomirski @ 2020-09-21 23:51 UTC (permalink / raw)
  To: Pavel Begunkov
  Cc: Arnd Bergmann, Andy Lutomirski, Christoph Hellwig, Al Viro,
	Andrew Morton, Jens Axboe, David Howells, linux-arm-kernel,
	X86 ML, LKML, open list:MIPS, Parisc List, linuxppc-dev,
	linux-s390, sparclinux, linux-block, Linux SCSI List,
	Linux FS Devel, linux-aio, io-uring, linux-arch, Linux-MM,
	Network Development, keyrings, LSM List

On Mon, Sep 21, 2020 at 9:15 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
>
> On 21/09/2020 19:10, Pavel Begunkov wrote:
> > On 20/09/2020 01:22, Andy Lutomirski wrote:
> >>
> >>> On Sep 19, 2020, at 2:16 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> >>>
> >>> On Sat, Sep 19, 2020 at 6:21 PM Andy Lutomirski <luto@kernel.org> wrote:
> >>>>> On Fri, Sep 18, 2020 at 8:16 AM Christoph Hellwig <hch@lst.de> wrote:
> >>>>> On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
> >>>>>> Said that, why not provide a variant that would take an explicit
> >>>>>> "is it compat" argument and use it there?  And have the normal
> >>>>>> one pass in_compat_syscall() to that...
> >>>>>
> >>>>> That would help to not introduce a regression with this series yes.
> >>>>> But it wouldn't fix existing bugs when io_uring is used to access
> >>>>> read or write methods that use in_compat_syscall().  One example that
> >>>>> I recently ran into is drivers/scsi/sg.c.
> >>>
> >>> Ah, so reading /dev/input/event* would suffer from the same issue,
> >>> and that one would in fact be broken by your patch in the hypothetical
> >>> case that someone tried to use io_uring to read /dev/input/event on x32...
> >>>
> >>> For reference, I checked the socket timestamp handling that has a
> >>> number of corner cases with time32/time64 formats in compat mode,
> >>> but none of those appear to be affected by the problem.
> >>>
> >>>> Aside from the potentially nasty use of per-task variables, one thing
> >>>> I don't like about PF_FORCE_COMPAT is that it's one-way.  If we're
> >>>> going to have a generic mechanism for this, shouldn't we allow a full
> >>>> override of the syscall arch instead of just allowing forcing compat
> >>>> so that a compat syscall can do a non-compat operation?
> >>>
> >>> The only reason it's needed here is that the caller is in a kernel
> >>> thread rather than a system call. Are there any possible scenarios
> >>> where one would actually need the opposite?
> >>>
> >>
> >> I can certainly imagine needing to force x32 mode from a kernel thread.
> >>
> >> As for the other direction: what exactly are the desired bitness/arch semantics of io_uring?  Is the operation bitness chosen by the io_uring creation or by the io_uring_enter() bitness?
> >
> > It's rather the second one. Even though AFAIR it wasn't discussed
> > specifically, that how it works now (_partially_).
>
> Double checked -- I'm wrong, that's the former one. Most of it is based
> on a flag that was set an creation.
>

Could we get away with making io_uring_enter() return -EINVAL (or
maybe -ENOTTY?) if you try to do it with bitness that doesn't match
the io_uring?  And disable SQPOLL in compat mode?

--Andy

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-21 23:51                     ` Andy Lutomirski
@ 2020-09-22  0:22                       ` Pavel Begunkov
  2020-09-22  0:58                         ` Andy Lutomirski
  0 siblings, 1 reply; 67+ messages in thread
From: Pavel Begunkov @ 2020-09-22  0:22 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: Arnd Bergmann, Christoph Hellwig, Al Viro, Andrew Morton,
	Jens Axboe, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List



On 22/09/2020 02:51, Andy Lutomirski wrote:
> On Mon, Sep 21, 2020 at 9:15 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>
>> On 21/09/2020 19:10, Pavel Begunkov wrote:
>>> On 20/09/2020 01:22, Andy Lutomirski wrote:
>>>>
>>>>> On Sep 19, 2020, at 2:16 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>>>>>
>>>>> On Sat, Sep 19, 2020 at 6:21 PM Andy Lutomirski <luto@kernel.org> wrote:
>>>>>>> On Fri, Sep 18, 2020 at 8:16 AM Christoph Hellwig <hch@lst.de> wrote:
>>>>>>> On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
>>>>>>>> Said that, why not provide a variant that would take an explicit
>>>>>>>> "is it compat" argument and use it there?  And have the normal
>>>>>>>> one pass in_compat_syscall() to that...
>>>>>>>
>>>>>>> That would help to not introduce a regression with this series yes.
>>>>>>> But it wouldn't fix existing bugs when io_uring is used to access
>>>>>>> read or write methods that use in_compat_syscall().  One example that
>>>>>>> I recently ran into is drivers/scsi/sg.c.
>>>>>
>>>>> Ah, so reading /dev/input/event* would suffer from the same issue,
>>>>> and that one would in fact be broken by your patch in the hypothetical
>>>>> case that someone tried to use io_uring to read /dev/input/event on x32...
>>>>>
>>>>> For reference, I checked the socket timestamp handling that has a
>>>>> number of corner cases with time32/time64 formats in compat mode,
>>>>> but none of those appear to be affected by the problem.
>>>>>
>>>>>> Aside from the potentially nasty use of per-task variables, one thing
>>>>>> I don't like about PF_FORCE_COMPAT is that it's one-way.  If we're
>>>>>> going to have a generic mechanism for this, shouldn't we allow a full
>>>>>> override of the syscall arch instead of just allowing forcing compat
>>>>>> so that a compat syscall can do a non-compat operation?
>>>>>
>>>>> The only reason it's needed here is that the caller is in a kernel
>>>>> thread rather than a system call. Are there any possible scenarios
>>>>> where one would actually need the opposite?
>>>>>
>>>>
>>>> I can certainly imagine needing to force x32 mode from a kernel thread.
>>>>
>>>> As for the other direction: what exactly are the desired bitness/arch semantics of io_uring?  Is the operation bitness chosen by the io_uring creation or by the io_uring_enter() bitness?
>>>
>>> It's rather the second one. Even though AFAIR it wasn't discussed
>>> specifically, that how it works now (_partially_).
>>
>> Double checked -- I'm wrong, that's the former one. Most of it is based
>> on a flag that was set an creation.
>>
> 
> Could we get away with making io_uring_enter() return -EINVAL (or
> maybe -ENOTTY?) if you try to do it with bitness that doesn't match
> the io_uring?  And disable SQPOLL in compat mode?

Something like below. If PF_FORCE_COMPAT or any other solution
doesn't lend by the time, I'll take a look whether other io_uring's
syscalls need similar checks, etc.


diff --git a/fs/io_uring.c b/fs/io_uring.c
index 0458f02d4ca8..aab20785fa9a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8671,6 +8671,10 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
 	if (ctx->flags & IORING_SETUP_R_DISABLED)
 		goto out;
 
+	ret = -EINVAl;
+	if (ctx->compat != in_compat_syscall())
+		goto out;
+
 	/*
 	 * For SQ polling, the thread will do all submissions and completions.
 	 * Just return the requested submit count, and wake the thread if
@@ -9006,6 +9010,10 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p,
 	if (ret)
 		goto err;
 
+	ret = -EINVAL;
+	if (ctx->compat)
+		goto err;
+
 	/* Only gets the ring fd, doesn't install it in the file table */
 	fd = io_uring_get_fd(ctx, &file);
 	if (fd < 0) {
-- 
Pavel Begunkov

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-22  0:22                       ` Pavel Begunkov
@ 2020-09-22  0:58                         ` Andy Lutomirski
  2020-09-22  6:30                           ` Pavel Begunkov
  0 siblings, 1 reply; 67+ messages in thread
From: Andy Lutomirski @ 2020-09-22  0:58 UTC (permalink / raw)
  To: Pavel Begunkov
  Cc: Andy Lutomirski, Arnd Bergmann, Christoph Hellwig, Al Viro,
	Andrew Morton, Jens Axboe, David Howells, linux-arm-kernel,
	X86 ML, LKML, open list:MIPS, Parisc List, linuxppc-dev,
	linux-s390, sparclinux, linux-block, Linux SCSI List,
	Linux FS Devel, linux-aio, io-uring, linux-arch, Linux-MM,
	Network Development, keyrings, LSM List

On Mon, Sep 21, 2020 at 5:24 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>
>
>
> On 22/09/2020 02:51, Andy Lutomirski wrote:
> > On Mon, Sep 21, 2020 at 9:15 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
> >>
> >> On 21/09/2020 19:10, Pavel Begunkov wrote:
> >>> On 20/09/2020 01:22, Andy Lutomirski wrote:
> >>>>
> >>>>> On Sep 19, 2020, at 2:16 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> >>>>>
> >>>>> On Sat, Sep 19, 2020 at 6:21 PM Andy Lutomirski <luto@kernel.org> wrote:
> >>>>>>> On Fri, Sep 18, 2020 at 8:16 AM Christoph Hellwig <hch@lst.de> wrote:
> >>>>>>> On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
> >>>>>>>> Said that, why not provide a variant that would take an explicit
> >>>>>>>> "is it compat" argument and use it there?  And have the normal
> >>>>>>>> one pass in_compat_syscall() to that...
> >>>>>>>
> >>>>>>> That would help to not introduce a regression with this series yes.
> >>>>>>> But it wouldn't fix existing bugs when io_uring is used to access
> >>>>>>> read or write methods that use in_compat_syscall().  One example that
> >>>>>>> I recently ran into is drivers/scsi/sg.c.
> >>>>>
> >>>>> Ah, so reading /dev/input/event* would suffer from the same issue,
> >>>>> and that one would in fact be broken by your patch in the hypothetical
> >>>>> case that someone tried to use io_uring to read /dev/input/event on x32...
> >>>>>
> >>>>> For reference, I checked the socket timestamp handling that has a
> >>>>> number of corner cases with time32/time64 formats in compat mode,
> >>>>> but none of those appear to be affected by the problem.
> >>>>>
> >>>>>> Aside from the potentially nasty use of per-task variables, one thing
> >>>>>> I don't like about PF_FORCE_COMPAT is that it's one-way.  If we're
> >>>>>> going to have a generic mechanism for this, shouldn't we allow a full
> >>>>>> override of the syscall arch instead of just allowing forcing compat
> >>>>>> so that a compat syscall can do a non-compat operation?
> >>>>>
> >>>>> The only reason it's needed here is that the caller is in a kernel
> >>>>> thread rather than a system call. Are there any possible scenarios
> >>>>> where one would actually need the opposite?
> >>>>>
> >>>>
> >>>> I can certainly imagine needing to force x32 mode from a kernel thread.
> >>>>
> >>>> As for the other direction: what exactly are the desired bitness/arch semantics of io_uring?  Is the operation bitness chosen by the io_uring creation or by the io_uring_enter() bitness?
> >>>
> >>> It's rather the second one. Even though AFAIR it wasn't discussed
> >>> specifically, that how it works now (_partially_).
> >>
> >> Double checked -- I'm wrong, that's the former one. Most of it is based
> >> on a flag that was set an creation.
> >>
> >
> > Could we get away with making io_uring_enter() return -EINVAL (or
> > maybe -ENOTTY?) if you try to do it with bitness that doesn't match
> > the io_uring?  And disable SQPOLL in compat mode?
>
> Something like below. If PF_FORCE_COMPAT or any other solution
> doesn't lend by the time, I'll take a look whether other io_uring's
> syscalls need similar checks, etc.
>
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 0458f02d4ca8..aab20785fa9a 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -8671,6 +8671,10 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
>         if (ctx->flags & IORING_SETUP_R_DISABLED)
>                 goto out;
>
> +       ret = -EINVAl;
> +       if (ctx->compat != in_compat_syscall())
> +               goto out;
> +

This seems entirely reasonable to me.  Sharing an io_uring ring
between programs with different ABIs seems a bit nutty.

>         /*
>          * For SQ polling, the thread will do all submissions and completions.
>          * Just return the requested submit count, and wake the thread if
> @@ -9006,6 +9010,10 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p,
>         if (ret)
>                 goto err;
>
> +       ret = -EINVAL;
> +       if (ctx->compat)
> +               goto err;
> +

I may be looking at a different kernel than you, but aren't you
preventing creating an io_uring regardless of whether SQPOLL is
requested?

>         /* Only gets the ring fd, doesn't install it in the file table */
>         fd = io_uring_get_fd(ctx, &file);
>         if (fd < 0) {
> --
> Pavel Begunkov

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-22  0:58                         ` Andy Lutomirski
@ 2020-09-22  6:30                           ` Pavel Begunkov
  2020-09-22  7:23                             ` Arnd Bergmann
  0 siblings, 1 reply; 67+ messages in thread
From: Pavel Begunkov @ 2020-09-22  6:30 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: Arnd Bergmann, Christoph Hellwig, Al Viro, Andrew Morton,
	Jens Axboe, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List

On 22/09/2020 03:58, Andy Lutomirski wrote:
> On Mon, Sep 21, 2020 at 5:24 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>>>>>> Ah, so reading /dev/input/event* would suffer from the same issue,
>>>>>>> and that one would in fact be broken by your patch in the hypothetical
>>>>>>> case that someone tried to use io_uring to read /dev/input/event on x32...
>>>>>>>
>>>>>>> For reference, I checked the socket timestamp handling that has a
>>>>>>> number of corner cases with time32/time64 formats in compat mode,
>>>>>>> but none of those appear to be affected by the problem.
>>>>>>>
>>>>>>>> Aside from the potentially nasty use of per-task variables, one thing
>>>>>>>> I don't like about PF_FORCE_COMPAT is that it's one-way.  If we're
>>>>>>>> going to have a generic mechanism for this, shouldn't we allow a full
>>>>>>>> override of the syscall arch instead of just allowing forcing compat
>>>>>>>> so that a compat syscall can do a non-compat operation?
>>>>>>>
>>>>>>> The only reason it's needed here is that the caller is in a kernel
>>>>>>> thread rather than a system call. Are there any possible scenarios
>>>>>>> where one would actually need the opposite?
>>>>>>>
>>>>>>
>>>>>> I can certainly imagine needing to force x32 mode from a kernel thread.
>>>>>>
>>>>>> As for the other direction: what exactly are the desired bitness/arch semantics of io_uring?  Is the operation bitness chosen by the io_uring creation or by the io_uring_enter() bitness?
>>>>>
>>>>> It's rather the second one. Even though AFAIR it wasn't discussed
>>>>> specifically, that how it works now (_partially_).
>>>>
>>>> Double checked -- I'm wrong, that's the former one. Most of it is based
>>>> on a flag that was set an creation.
>>>>
>>>
>>> Could we get away with making io_uring_enter() return -EINVAL (or
>>> maybe -ENOTTY?) if you try to do it with bitness that doesn't match
>>> the io_uring?  And disable SQPOLL in compat mode?
>>
>> Something like below. If PF_FORCE_COMPAT or any other solution
>> doesn't lend by the time, I'll take a look whether other io_uring's
>> syscalls need similar checks, etc.
>>
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index 0458f02d4ca8..aab20785fa9a 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -8671,6 +8671,10 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
>>         if (ctx->flags & IORING_SETUP_R_DISABLED)
>>                 goto out;
>>
>> +       ret = -EINVAl;
>> +       if (ctx->compat != in_compat_syscall())
>> +               goto out;
>> +
> 
> This seems entirely reasonable to me.  Sharing an io_uring ring
> between programs with different ABIs seems a bit nutty.
> 
>>         /*
>>          * For SQ polling, the thread will do all submissions and completions.
>>          * Just return the requested submit count, and wake the thread if
>> @@ -9006,6 +9010,10 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p,
>>         if (ret)
>>                 goto err;
>>
>> +       ret = -EINVAL;
>> +       if (ctx->compat)
>> +               goto err;
>> +
> 
> I may be looking at a different kernel than you, but aren't you
> preventing creating an io_uring regardless of whether SQPOLL is
> requested?

I diffed a not-saved file on a sleepy head, thanks for noticing.
As you said, there should be an SQPOLL check.

...
if (ctx->compat && (p->flags & IORING_SETUP_SQPOLL))
	goto err;

-- 
Pavel Begunkov

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-22  6:30                           ` Pavel Begunkov
@ 2020-09-22  7:23                             ` Arnd Bergmann
  2020-09-22  7:57                               ` Pavel Begunkov
  0 siblings, 1 reply; 67+ messages in thread
From: Arnd Bergmann @ 2020-09-22  7:23 UTC (permalink / raw)
  To: Pavel Begunkov
  Cc: Andy Lutomirski, Christoph Hellwig, Al Viro, Andrew Morton,
	Jens Axboe, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List

On Tue, Sep 22, 2020 at 8:32 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
> On 22/09/2020 03:58, Andy Lutomirski wrote:
> > On Mon, Sep 21, 2020 at 5:24 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
> > I may be looking at a different kernel than you, but aren't you
> > preventing creating an io_uring regardless of whether SQPOLL is
> > requested?
>
> I diffed a not-saved file on a sleepy head, thanks for noticing.
> As you said, there should be an SQPOLL check.
>
> ...
> if (ctx->compat && (p->flags & IORING_SETUP_SQPOLL))
>         goto err;

Wouldn't that mean that now 32-bit containers behave differently
between compat and native execution?

I think if you want to prevent 32-bit applications from using SQPOLL,
it needs to be done the same way on both to be consistent:

   if ((!IS_ENABLED(CONFIG_64BIT) || ctx->compat) &&
        (p->flags & IORING_SETUP_SQPOLL))
            goto err;

I don't really see how taking away SQPOLL from 32-bit tasks is
any better than just preventing access to the known-broken files
as Al suggested, or adding the hack to make it work as in
Christoph's original patch.

Can we expect all existing and future user space to have a sane
fallback when IORING_SETUP_SQPOLL fails?

      Arnd

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-22  7:23                             ` Arnd Bergmann
@ 2020-09-22  7:57                               ` Pavel Begunkov
  2020-09-22  9:01                                 ` Arnd Bergmann
  0 siblings, 1 reply; 67+ messages in thread
From: Pavel Begunkov @ 2020-09-22  7:57 UTC (permalink / raw)
  To: Arnd Bergmann
  Cc: Andy Lutomirski, Christoph Hellwig, Al Viro, Andrew Morton,
	Jens Axboe, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List

On 22/09/2020 10:23, Arnd Bergmann wrote:
> On Tue, Sep 22, 2020 at 8:32 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
>> On 22/09/2020 03:58, Andy Lutomirski wrote:
>>> On Mon, Sep 21, 2020 at 5:24 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>> I may be looking at a different kernel than you, but aren't you
>>> preventing creating an io_uring regardless of whether SQPOLL is
>>> requested?
>>
>> I diffed a not-saved file on a sleepy head, thanks for noticing.
>> As you said, there should be an SQPOLL check.
>>
>> ...
>> if (ctx->compat && (p->flags & IORING_SETUP_SQPOLL))
>>         goto err;
> 
> Wouldn't that mean that now 32-bit containers behave differently
> between compat and native execution?
> 
> I think if you want to prevent 32-bit applications from using SQPOLL,
> it needs to be done the same way on both to be consistent:

The intention was to disable only compat not native 32-bit.

> 
>    if ((!IS_ENABLED(CONFIG_64BIT) || ctx->compat) &&
>         (p->flags & IORING_SETUP_SQPOLL))
>             goto err;
> 
> I don't really see how taking away SQPOLL from 32-bit tasks is
> any better than just preventing access to the known-broken files
> as Al suggested, or adding the hack to make it work as in
> Christoph's original patch.

That's why I'm hoping that Christoph's work and the discussion will
reach consensus, but the bug should be patched in the end. IMHO,
it's a good and easy enough fallback option (temporal?).

> 
> Can we expect all existing and future user space to have a sane
> fallback when IORING_SETUP_SQPOLL fails?

SQPOLL has a few differences with non-SQPOLL modes, but it's easy
to convert between them. Anyway, SQPOLL is a privileged special
case that's here for performance/latency reasons, I don't think
there will be any non-accidental users of it.
-- 
Pavel Begunkov

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-22  7:57                               ` Pavel Begunkov
@ 2020-09-22  9:01                                 ` Arnd Bergmann
  2020-09-22 16:20                                   ` Andy Lutomirski
  2020-09-23  8:01                                   ` Pavel Begunkov
  0 siblings, 2 replies; 67+ messages in thread
From: Arnd Bergmann @ 2020-09-22  9:01 UTC (permalink / raw)
  To: Pavel Begunkov
  Cc: Andy Lutomirski, Christoph Hellwig, Al Viro, Andrew Morton,
	Jens Axboe, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List

On Tue, Sep 22, 2020 at 9:59 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
> On 22/09/2020 10:23, Arnd Bergmann wrote:
> > On Tue, Sep 22, 2020 at 8:32 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
> >> On 22/09/2020 03:58, Andy Lutomirski wrote:
> >>> On Mon, Sep 21, 2020 at 5:24 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
> >>> I may be looking at a different kernel than you, but aren't you
> >>> preventing creating an io_uring regardless of whether SQPOLL is
> >>> requested?
> >>
> >> I diffed a not-saved file on a sleepy head, thanks for noticing.
> >> As you said, there should be an SQPOLL check.
> >>
> >> ...
> >> if (ctx->compat && (p->flags & IORING_SETUP_SQPOLL))
> >>         goto err;
> >
> > Wouldn't that mean that now 32-bit containers behave differently
> > between compat and native execution?
> >
> > I think if you want to prevent 32-bit applications from using SQPOLL,
> > it needs to be done the same way on both to be consistent:
>
> The intention was to disable only compat not native 32-bit.

I'm not following why that would be considered a valid option,
as that clearly breaks existing users that update from a 32-bit
kernel to a 64-bit one.

Taking away the features from users that are still on 32-bit kernels
already seems questionable to me, but being inconsistent
about it seems much worse, in particular when the regression
is on the upgrade path.

> > Can we expect all existing and future user space to have a sane
> > fallback when IORING_SETUP_SQPOLL fails?
>
> SQPOLL has a few differences with non-SQPOLL modes, but it's easy
> to convert between them. Anyway, SQPOLL is a privileged special
> case that's here for performance/latency reasons, I don't think
> there will be any non-accidental users of it.

Ok, so the behavior of 32-bit tasks would be the same as running
the same application as unprivileged 64-bit tasks, with applications
already having to implement that fallback, right?

      Arnd

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-22  9:01                                 ` Arnd Bergmann
@ 2020-09-22 16:20                                   ` Andy Lutomirski
  2020-09-23  8:01                                   ` Pavel Begunkov
  1 sibling, 0 replies; 67+ messages in thread
From: Andy Lutomirski @ 2020-09-22 16:20 UTC (permalink / raw)
  To: Arnd Bergmann
  Cc: Pavel Begunkov, Andy Lutomirski, Christoph Hellwig, Al Viro,
	Andrew Morton, Jens Axboe, David Howells, linux-arm-kernel,
	X86 ML, LKML, open list:MIPS, Parisc List, linuxppc-dev,
	linux-s390, sparclinux, linux-block, Linux SCSI List,
	Linux FS Devel, linux-aio, io-uring, linux-arch, Linux-MM,
	Network Development, keyrings, LSM List



> On Sep 22, 2020, at 2:01 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> 
> On Tue, Sep 22, 2020 at 9:59 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>> On 22/09/2020 10:23, Arnd Bergmann wrote:
>>> On Tue, Sep 22, 2020 at 8:32 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>>> On 22/09/2020 03:58, Andy Lutomirski wrote:
>>>>> On Mon, Sep 21, 2020 at 5:24 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>>>> I may be looking at a different kernel than you, but aren't you
>>>>> preventing creating an io_uring regardless of whether SQPOLL is
>>>>> requested?
>>>> 
>>>> I diffed a not-saved file on a sleepy head, thanks for noticing.
>>>> As you said, there should be an SQPOLL check.
>>>> 
>>>> ...
>>>> if (ctx->compat && (p->flags & IORING_SETUP_SQPOLL))
>>>>        goto err;
>>> 
>>> Wouldn't that mean that now 32-bit containers behave differently
>>> between compat and native execution?
>>> 
>>> I think if you want to prevent 32-bit applications from using SQPOLL,
>>> it needs to be done the same way on both to be consistent:
>> 
>> The intention was to disable only compat not native 32-bit.
> 
> I'm not following why that would be considered a valid option,
> as that clearly breaks existing users that update from a 32-bit
> kernel to a 64-bit one.
> 
> Taking away the features from users that are still on 32-bit kernels
> already seems questionable to me, but being inconsistent
> about it seems much worse, in particular when the regression
> is on the upgrade path.
> 
>>> Can we expect all existing and future user space to have a sane
>>> fallback when IORING_SETUP_SQPOLL fails?
>> 
>> SQPOLL has a few differences with non-SQPOLL modes, but it's easy
>> to convert between them. Anyway, SQPOLL is a privileged special
>> case that's here for performance/latency reasons, I don't think
>> there will be any non-accidental users of it.
> 
> Ok, so the behavior of 32-bit tasks would be the same as running
> the same application as unprivileged 64-bit tasks, with applications
> already having to implement that fallback, right?
> 
> 

I don’t have any real preference wrt SQPOLL, and it may be that we have a problem even without SQPOLL when IO gets punted without one of the fixes discussed.

But banning the mismatched io_uring and io_uring_enter seems like it may be worthwhile regardless.

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-22  9:01                                 ` Arnd Bergmann
  2020-09-22 16:20                                   ` Andy Lutomirski
@ 2020-09-23  8:01                                   ` Pavel Begunkov
  2020-09-23 13:22                                     ` Al Viro
  1 sibling, 1 reply; 67+ messages in thread
From: Pavel Begunkov @ 2020-09-23  8:01 UTC (permalink / raw)
  To: Arnd Bergmann
  Cc: Andy Lutomirski, Christoph Hellwig, Al Viro, Andrew Morton,
	Jens Axboe, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List

On 22/09/2020 12:01, Arnd Bergmann wrote:
> On Tue, Sep 22, 2020 at 9:59 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
>> On 22/09/2020 10:23, Arnd Bergmann wrote:
>>> On Tue, Sep 22, 2020 at 8:32 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>>> On 22/09/2020 03:58, Andy Lutomirski wrote:
>>>>> On Mon, Sep 21, 2020 at 5:24 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>>>> I may be looking at a different kernel than you, but aren't you
>>>>> preventing creating an io_uring regardless of whether SQPOLL is
>>>>> requested?
>>>>
>>>> I diffed a not-saved file on a sleepy head, thanks for noticing.
>>>> As you said, there should be an SQPOLL check.
>>>>
>>>> ...
>>>> if (ctx->compat && (p->flags & IORING_SETUP_SQPOLL))
>>>>         goto err;
>>>
>>> Wouldn't that mean that now 32-bit containers behave differently
>>> between compat and native execution?
>>>
>>> I think if you want to prevent 32-bit applications from using SQPOLL,
>>> it needs to be done the same way on both to be consistent:
>>
>> The intention was to disable only compat not native 32-bit.
> 
> I'm not following why that would be considered a valid option,
> as that clearly breaks existing users that update from a 32-bit
> kernel to a 64-bit one.

Do you mean users who move 32-bit binaries (without recompiling) to a
new x64 kernel? Does the kernel guarantees that to work? I'd personally
care more native-bitness apps.

> 
> Taking away the features from users that are still on 32-bit kernels
> already seems questionable to me, but being inconsistent
> about it seems much worse, in particular when the regression
> is on the upgrade path.

TBH, this won't fix that entirely (e.g. passing non-compat io_uring
to a compat process should yield the same problem). So, let's put
it aside for now until this bikeshedding would be relevant.

> 
>>> Can we expect all existing and future user space to have a sane
>>> fallback when IORING_SETUP_SQPOLL fails?
>>
>> SQPOLL has a few differences with non-SQPOLL modes, but it's easy
>> to convert between them. Anyway, SQPOLL is a privileged special
>> case that's here for performance/latency reasons, I don't think
>> there will be any non-accidental users of it.
> 
> Ok, so the behavior of 32-bit tasks would be the same as running
> the same application as unprivileged 64-bit tasks, with applications

Yes, something like that, but that's not automatic and in some
(hopefully rare) cases there may be pitfalls. That's in short,
I can expand the idea a bit if anyone would be interested.

> already having to implement that fallback, right?

Well, not everyone _have_ to implement such a fallback, e.g.
applications working only whilst privileged may use SQPOLL only.

-- 
Pavel Begunkov

^ permalink raw reply	[flat|nested] 67+ messages in thread

* Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
  2020-09-23  8:01                                   ` Pavel Begunkov
@ 2020-09-23 13:22                                     ` Al Viro
  0 siblings, 0 replies; 67+ messages in thread
From: Al Viro @ 2020-09-23 13:22 UTC (permalink / raw)
  To: Pavel Begunkov
  Cc: Arnd Bergmann, Andy Lutomirski, Christoph Hellwig, Andrew Morton,
	Jens Axboe, David Howells, linux-arm-kernel, X86 ML, LKML,
	open list:MIPS, Parisc List, linuxppc-dev, linux-s390,
	sparclinux, linux-block, Linux SCSI List, Linux FS Devel,
	linux-aio, io-uring, linux-arch, Linux-MM, Network Development,
	keyrings, LSM List

On Wed, Sep 23, 2020 at 11:01:34AM +0300, Pavel Begunkov wrote:

> > I'm not following why that would be considered a valid option,
> > as that clearly breaks existing users that update from a 32-bit
> > kernel to a 64-bit one.
> 
> Do you mean users who move 32-bit binaries (without recompiling) to a
> new x64 kernel? Does the kernel guarantees that to work?

Yes.

No further (printable) comments for now...

^ permalink raw reply	[flat|nested] 67+ messages in thread

end of thread, back to index

Thread overview: 67+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-09-18 12:45 let import_iovec deal with compat_iovecs as well Christoph Hellwig
2020-09-18 12:45 ` [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag Christoph Hellwig
2020-09-18 13:40   ` Al Viro
2020-09-18 13:44     ` Christoph Hellwig
2020-09-18 13:58       ` Al Viro
2020-09-18 15:16         ` Christoph Hellwig
2020-09-19 16:21           ` Andy Lutomirski
2020-09-19 21:16             ` Arnd Bergmann
2020-09-19 21:52               ` Finn Thain
2020-09-19 22:22               ` Andy Lutomirski
2020-09-21 16:10                 ` Pavel Begunkov
2020-09-21 16:13                   ` Pavel Begunkov
2020-09-21 23:51                     ` Andy Lutomirski
2020-09-22  0:22                       ` Pavel Begunkov
2020-09-22  0:58                         ` Andy Lutomirski
2020-09-22  6:30                           ` Pavel Begunkov
2020-09-22  7:23                             ` Arnd Bergmann
2020-09-22  7:57                               ` Pavel Begunkov
2020-09-22  9:01                                 ` Arnd Bergmann
2020-09-22 16:20                                   ` Andy Lutomirski
2020-09-23  8:01                                   ` Pavel Begunkov
2020-09-23 13:22                                     ` Al Viro
2020-09-19 22:09           ` Al Viro
2020-09-19 22:23             ` Andy Lutomirski
2020-09-19 22:41               ` Al Viro
2020-09-19 22:53                 ` Andy Lutomirski
2020-09-19 23:24                   ` Al Viro
2020-09-20  0:14                     ` Andy Lutomirski
2020-09-20  2:57                       ` Al Viro
2020-09-20 16:59                         ` Andy Lutomirski
2020-09-20 18:12                           ` Al Viro
2020-09-20 13:55             ` Arnd Bergmann
2020-09-20 15:02               ` Al Viro
2020-09-19 14:53         ` David Laight
2020-09-18 13:59       ` Arnd Bergmann
2020-09-20 15:15   ` Matthew Wilcox
2020-09-20 15:55     ` William Kucharski
2020-09-21 16:20       ` Pavel Begunkov
2020-09-20 16:00     ` Arnd Bergmann
2020-09-20 18:07     ` Al Viro
2020-09-20 18:41       ` Al Viro
2020-09-20 19:01       ` Matthew Wilcox
2020-09-20 19:10         ` Al Viro
2020-09-20 19:22           ` Matthew Wilcox
2020-09-20 19:28             ` Andy Lutomirski
2020-09-20 20:49               ` Arnd Bergmann
2020-09-20 21:13                 ` David Laight
2020-09-21 16:31                   ` Pavel Begunkov
2020-09-20 21:42             ` Al Viro
2020-09-21 16:26             ` Pavel Begunkov
2020-09-20 19:14       ` Andy Lutomirski
2020-09-21  4:28         ` Christoph Hellwig
2020-09-18 12:45 ` [PATCH 2/9] compat.h: fix a spelling error in <linux/compat.h> Christoph Hellwig
2020-09-18 13:37   ` Johannes Thumshirn
2020-09-18 12:45 ` [PATCH 3/9] fs: explicitly check for CHECK_IOVEC_ONLY in rw_copy_check_uvector Christoph Hellwig
2020-09-18 12:56   ` Matthew Wilcox
2020-09-18 13:39   ` Johannes Thumshirn
2020-09-18 12:45 ` [PATCH 4/9] fs: handle the compat case in import_iovec Christoph Hellwig
2020-09-18 12:45 ` [PATCH 5/9] fs: remove various compat readv/writev helpers Christoph Hellwig
2020-09-18 12:45 ` [PATCH 6/9] fs: remove the compat readv/writev syscalls Christoph Hellwig
2020-09-18 12:45 ` [PATCH 7/9] fs: remove compat_sys_vmsplice Christoph Hellwig
2020-09-18 12:45 ` [PATCH 8/9] mm: remove compat_process_vm_{readv,writev} Christoph Hellwig
2020-09-18 13:48   ` Arnd Bergmann
2020-09-18 12:45 ` [PATCH 9/9] security/keys: remove compat_keyctl_instantiate_key_iov Christoph Hellwig
2020-09-19 14:24 ` let import_iovec deal with compat_iovecs as well David Laight
2020-09-21  4:41   ` 'Christoph Hellwig'
2020-09-21 11:11     ` David Laight

Linux-Fsdevel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-fsdevel/0 linux-fsdevel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-fsdevel linux-fsdevel/ https://lore.kernel.org/linux-fsdevel \
		linux-fsdevel@vger.kernel.org
	public-inbox-index linux-fsdevel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-fsdevel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git