improve compat handling for the i386 u64 alignment quirk v2

improve compat handling for the i386 u64 alignment quirk v2

[Christoph Hellwig]

Hi all,

the i386 ABI is a little special in that it uses less than natural
alignment for 64-bit integer types (u64 and s64), and a significant
amount of our compat handlers deals with just that.  Unfortunately
there is no good way to check for this specific quirk at runtime,
similar how in_compat_syscall() checks for a compat syscall.  This
series adds such a check, and then uses the quota code as an example
of how this improves the compat handling.  I have a few other places
in mind where this will also be useful going forward.

Changes since v1:
 - use asm-generic/compat.h instead of linux/compat.h for
   compat_u64 and compat_s64
 - fix a typo

Diffstat:
 b/arch/arm64/include/asm/compat.h        |    2 
 b/arch/mips/include/asm/compat.h         |    2 
 b/arch/parisc/include/asm/compat.h       |    2 
 b/arch/powerpc/include/asm/compat.h      |    2 
 b/arch/s390/include/asm/compat.h         |    2 
 b/arch/sparc/include/asm/compat.h        |    3 
 b/arch/x86/entry/syscalls/syscall_32.tbl |    2 
 b/arch/x86/include/asm/compat.h          |    3 
 b/fs/quota/Kconfig                       |    5 -
 b/fs/quota/Makefile                      |    1 
 b/fs/quota/compat.h                      |   34 ++++++++
 b/fs/quota/quota.c                       |   73 +++++++++++++++---
 b/include/asm-generic/compat.h           |    8 ++
 b/include/linux/compat.h                 |    9 ++
 b/include/linux/quotaops.h               |    3 
 b/kernel/sys_ni.c                        |    1 
 fs/quota/compat.c                        |  120 -------------------------------
 17 files changed, 113 insertions(+), 159 deletions(-)

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[PATCH 1/3] compat: lift compat_s64 and compat_u64 to <asm-generic/compat.h>

[Christoph Hellwig]

lift the compat_s64 and compat_u64 definitions into common code using the
COMPAT_FOR_U64_ALIGNMENT symbol for the x86 special case.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/arm64/include/asm/compat.h   | 2 --
 arch/mips/include/asm/compat.h    | 2 --
 arch/parisc/include/asm/compat.h  | 2 --
 arch/powerpc/include/asm/compat.h | 2 --
 arch/s390/include/asm/compat.h    | 2 --
 arch/sparc/include/asm/compat.h   | 3 +--
 arch/x86/include/asm/compat.h     | 2 --
 include/asm-generic/compat.h      | 8 ++++++++
 8 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/arch/arm64/include/asm/compat.h b/arch/arm64/include/asm/compat.h
index 935d2aa231bf06..23a9fb73c04ff8 100644
--- a/arch/arm64/include/asm/compat.h
+++ b/arch/arm64/include/asm/compat.h
@@ -35,8 +35,6 @@ typedef s32		compat_nlink_t;
 typedef u16		compat_ipc_pid_t;
 typedef u32		compat_caddr_t;
 typedef __kernel_fsid_t	compat_fsid_t;
-typedef s64		compat_s64;
-typedef u64		compat_u64;
 
 struct compat_stat {
 #ifdef __AARCH64EB__
diff --git a/arch/mips/include/asm/compat.h b/arch/mips/include/asm/compat.h
index 255afcdd79c94b..65975712a22dcf 100644
--- a/arch/mips/include/asm/compat.h
+++ b/arch/mips/include/asm/compat.h
@@ -26,8 +26,6 @@ typedef s32		compat_caddr_t;
 typedef struct {
 	s32	val[2];
 } compat_fsid_t;
-typedef s64		compat_s64;
-typedef u64		compat_u64;
 
 struct compat_stat {
 	compat_dev_t	st_dev;
diff --git a/arch/parisc/include/asm/compat.h b/arch/parisc/include/asm/compat.h
index 2f4f66a3bac079..8f33085ff1bd88 100644
--- a/arch/parisc/include/asm/compat.h
+++ b/arch/parisc/include/asm/compat.h
@@ -22,8 +22,6 @@ typedef u32	compat_dev_t;
 typedef u16	compat_nlink_t;
 typedef u16	compat_ipc_pid_t;
 typedef u32	compat_caddr_t;
-typedef s64	compat_s64;
-typedef u64	compat_u64;
 
 struct compat_stat {
 	compat_dev_t		st_dev;	/* dev_t is 32 bits on parisc */
diff --git a/arch/powerpc/include/asm/compat.h b/arch/powerpc/include/asm/compat.h
index 3e3cdfaa76c6a5..9191fc29e6ed11 100644
--- a/arch/powerpc/include/asm/compat.h
+++ b/arch/powerpc/include/asm/compat.h
@@ -27,8 +27,6 @@ typedef s16		compat_nlink_t;
 typedef u16		compat_ipc_pid_t;
 typedef u32		compat_caddr_t;
 typedef __kernel_fsid_t	compat_fsid_t;
-typedef s64		compat_s64;
-typedef u64		compat_u64;
 
 struct compat_stat {
 	compat_dev_t	st_dev;
diff --git a/arch/s390/include/asm/compat.h b/arch/s390/include/asm/compat.h
index 9547cd5d6cdc21..ea5b9c34b7be5b 100644
--- a/arch/s390/include/asm/compat.h
+++ b/arch/s390/include/asm/compat.h
@@ -63,8 +63,6 @@ typedef u16		compat_nlink_t;
 typedef u16		compat_ipc_pid_t;
 typedef u32		compat_caddr_t;
 typedef __kernel_fsid_t	compat_fsid_t;
-typedef s64		compat_s64;
-typedef u64		compat_u64;
 
 typedef struct {
 	u32 mask;
diff --git a/arch/sparc/include/asm/compat.h b/arch/sparc/include/asm/compat.h
index 40a267b3bd5208..b85842cda99fe0 100644
--- a/arch/sparc/include/asm/compat.h
+++ b/arch/sparc/include/asm/compat.h
@@ -21,8 +21,7 @@ typedef s16		compat_nlink_t;
 typedef u16		compat_ipc_pid_t;
 typedef u32		compat_caddr_t;
 typedef __kernel_fsid_t	compat_fsid_t;
-typedef s64		compat_s64;
-typedef u64		compat_u64;
+
 struct compat_stat {
 	compat_dev_t	st_dev;
 	compat_ino_t	st_ino;
diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h
index d4edf281fff49d..bf547701f41f87 100644
--- a/arch/x86/include/asm/compat.h
+++ b/arch/x86/include/asm/compat.h
@@ -27,8 +27,6 @@ typedef u16		compat_nlink_t;
 typedef u16		compat_ipc_pid_t;
 typedef u32		compat_caddr_t;
 typedef __kernel_fsid_t	compat_fsid_t;
-typedef s64 __attribute__((aligned(4))) compat_s64;
-typedef u64 __attribute__((aligned(4))) compat_u64;
 
 struct compat_stat {
 	compat_dev_t	st_dev;
diff --git a/include/asm-generic/compat.h b/include/asm-generic/compat.h
index a86f65bffab8d0..30f7b18a36f939 100644
--- a/include/asm-generic/compat.h
+++ b/include/asm-generic/compat.h
@@ -22,4 +22,12 @@ typedef u32 compat_ulong_t;
 typedef u32 compat_uptr_t;
 typedef u32 compat_aio_context_t;
 
+#ifdef CONFIG_COMPAT_FOR_U64_ALIGNMENT
+typedef s64 __attribute__((aligned(4))) compat_s64;
+typedef u64 __attribute__((aligned(4))) compat_u64;
+#else
+typedef s64 compat_s64;
+typedef u64 compat_u64;
+#endif
+
 #endif
-- 
2.27.0


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[PATCH 2/3] compat: add a compat_need_64bit_alignment_fixup() helper

[Christoph Hellwig]

Add a helper to check if the calling syscall needs a fixup for
non-natural 64-bit type alignment in the compat ABI.  This will only
return true for i386 syscalls on x86_64.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/x86/include/asm/compat.h | 1 +
 include/linux/compat.h        | 9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h
index bf547701f41f87..0e327a01f50fbb 100644
--- a/arch/x86/include/asm/compat.h
+++ b/arch/x86/include/asm/compat.h
@@ -209,6 +209,7 @@ static inline bool in_compat_syscall(void)
 	return in_32bit_syscall();
 }
 #define in_compat_syscall in_compat_syscall	/* override the generic impl */
+#define compat_need_64bit_alignment_fixup in_ia32_syscall
 #endif
 
 struct compat_siginfo;
diff --git a/include/linux/compat.h b/include/linux/compat.h
index e90100c0de72e4..a195f90f156cf6 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -937,6 +937,15 @@ static inline bool in_compat_syscall(void) { return false; }
 
 #endif /* CONFIG_COMPAT */
 
+/*
+ * Some legacy ABIs like the i386 one use less than natural alignment for 64-bit
+ * types, and will need special compat treatment for that.  Most architectures
+ * don't need that special handling even for compat syscalls.
+ */
+#ifndef compat_need_64bit_alignment_fixup
+#define compat_need_64bit_alignment_fixup()		false
+#endif
+
 /*
  * A pointer passed in from user mode. This should not
  * be used for syscall parameters, just declare them
-- 
2.27.0


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[PATCH 3/3] quota: simplify the quotactl compat handling

[Christoph Hellwig]

Fold the misaligned u64 workarounds into the main quotactl flow instead
of implementing a separate compat syscall handler.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jan Kara <jack@suse.cz>
---
 arch/x86/entry/syscalls/syscall_32.tbl |   2 +-
 fs/quota/Kconfig                       |   5 --
 fs/quota/Makefile                      |   1 -
 fs/quota/compat.c                      | 120 -------------------------
 fs/quota/compat.h                      |  34 +++++++
 fs/quota/quota.c                       |  73 ++++++++++++---
 include/linux/quotaops.h               |   3 -
 kernel/sys_ni.c                        |   1 -
 8 files changed, 94 insertions(+), 145 deletions(-)
 delete mode 100644 fs/quota/compat.c
 create mode 100644 fs/quota/compat.h

diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index d8f8a1a69ed11f..41d442d7c2db67 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -142,7 +142,7 @@
 128	i386	init_module		sys_init_module
 129	i386	delete_module		sys_delete_module
 130	i386	get_kernel_syms
-131	i386	quotactl		sys_quotactl			compat_sys_quotactl32
+131	i386	quotactl		sys_quotactl
 132	i386	getpgid			sys_getpgid
 133	i386	fchdir			sys_fchdir
 134	i386	bdflush			sys_bdflush
diff --git a/fs/quota/Kconfig b/fs/quota/Kconfig
index 7218314ca13f00..4f5bb85099a904 100644
--- a/fs/quota/Kconfig
+++ b/fs/quota/Kconfig
@@ -70,8 +70,3 @@ config QFMT_V2
 config QUOTACTL
 	bool
 	default n
-
-config QUOTACTL_COMPAT
-	bool
-	depends on QUOTACTL && COMPAT_FOR_U64_ALIGNMENT
-	default y
diff --git a/fs/quota/Makefile b/fs/quota/Makefile
index f2b49d0f0287c9..9160639daffa75 100644
--- a/fs/quota/Makefile
+++ b/fs/quota/Makefile
@@ -4,5 +4,4 @@ obj-$(CONFIG_QFMT_V1)		+= quota_v1.o
 obj-$(CONFIG_QFMT_V2)		+= quota_v2.o
 obj-$(CONFIG_QUOTA_TREE)	+= quota_tree.o
 obj-$(CONFIG_QUOTACTL)		+= quota.o kqid.o
-obj-$(CONFIG_QUOTACTL_COMPAT)	+= compat.o
 obj-$(CONFIG_QUOTA_NETLINK_INTERFACE)	+= netlink.o
diff --git a/fs/quota/compat.c b/fs/quota/compat.c
deleted file mode 100644
index c305728576193d..00000000000000
--- a/fs/quota/compat.c
+++ /dev/null
@@ -1,120 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-
-#include <linux/syscalls.h>
-#include <linux/compat.h>
-#include <linux/quotaops.h>
-
-/*
- * This code works only for 32 bit quota tools over 64 bit OS (x86_64, ia64)
- * and is necessary due to alignment problems.
- */
-struct compat_if_dqblk {
-	compat_u64 dqb_bhardlimit;
-	compat_u64 dqb_bsoftlimit;
-	compat_u64 dqb_curspace;
-	compat_u64 dqb_ihardlimit;
-	compat_u64 dqb_isoftlimit;
-	compat_u64 dqb_curinodes;
-	compat_u64 dqb_btime;
-	compat_u64 dqb_itime;
-	compat_uint_t dqb_valid;
-};
-
-/* XFS structures */
-struct compat_fs_qfilestat {
-	compat_u64 dqb_bhardlimit;
-	compat_u64 qfs_nblks;
-	compat_uint_t qfs_nextents;
-};
-
-struct compat_fs_quota_stat {
-	__s8		qs_version;
-	__u16		qs_flags;
-	__s8		qs_pad;
-	struct compat_fs_qfilestat	qs_uquota;
-	struct compat_fs_qfilestat	qs_gquota;
-	compat_uint_t	qs_incoredqs;
-	compat_int_t	qs_btimelimit;
-	compat_int_t	qs_itimelimit;
-	compat_int_t	qs_rtbtimelimit;
-	__u16		qs_bwarnlimit;
-	__u16		qs_iwarnlimit;
-};
-
-COMPAT_SYSCALL_DEFINE4(quotactl32, unsigned int, cmd,
-		       const char __user *, special, qid_t, id,
-		       void __user *, addr)
-{
-	unsigned int cmds;
-	struct if_dqblk __user *dqblk;
-	struct compat_if_dqblk __user *compat_dqblk;
-	struct fs_quota_stat __user *fsqstat;
-	struct compat_fs_quota_stat __user *compat_fsqstat;
-	compat_uint_t data;
-	u16 xdata;
-	long ret;
-
-	cmds = cmd >> SUBCMDSHIFT;
-
-	switch (cmds) {
-	case Q_GETQUOTA:
-		dqblk = compat_alloc_user_space(sizeof(struct if_dqblk));
-		compat_dqblk = addr;
-		ret = kernel_quotactl(cmd, special, id, dqblk);
-		if (ret)
-			break;
-		if (copy_in_user(compat_dqblk, dqblk, sizeof(*compat_dqblk)) ||
-			get_user(data, &dqblk->dqb_valid) ||
-			put_user(data, &compat_dqblk->dqb_valid))
-			ret = -EFAULT;
-		break;
-	case Q_SETQUOTA:
-		dqblk = compat_alloc_user_space(sizeof(struct if_dqblk));
-		compat_dqblk = addr;
-		ret = -EFAULT;
-		if (copy_in_user(dqblk, compat_dqblk, sizeof(*compat_dqblk)) ||
-			get_user(data, &compat_dqblk->dqb_valid) ||
-			put_user(data, &dqblk->dqb_valid))
-			break;
-		ret = kernel_quotactl(cmd, special, id, dqblk);
-		break;
-	case Q_XGETQSTAT:
-		fsqstat = compat_alloc_user_space(sizeof(struct fs_quota_stat));
-		compat_fsqstat = addr;
-		ret = kernel_quotactl(cmd, special, id, fsqstat);
-		if (ret)
-			break;
-		ret = -EFAULT;
-		/* Copying qs_version, qs_flags, qs_pad */
-		if (copy_in_user(compat_fsqstat, fsqstat,
-			offsetof(struct compat_fs_quota_stat, qs_uquota)))
-			break;
-		/* Copying qs_uquota */
-		if (copy_in_user(&compat_fsqstat->qs_uquota,
-			&fsqstat->qs_uquota,
-			sizeof(compat_fsqstat->qs_uquota)) ||
-			get_user(data, &fsqstat->qs_uquota.qfs_nextents) ||
-			put_user(data, &compat_fsqstat->qs_uquota.qfs_nextents))
-			break;
-		/* Copying qs_gquota */
-		if (copy_in_user(&compat_fsqstat->qs_gquota,
-			&fsqstat->qs_gquota,
-			sizeof(compat_fsqstat->qs_gquota)) ||
-			get_user(data, &fsqstat->qs_gquota.qfs_nextents) ||
-			put_user(data, &compat_fsqstat->qs_gquota.qfs_nextents))
-			break;
-		/* Copying the rest */
-		if (copy_in_user(&compat_fsqstat->qs_incoredqs,
-			&fsqstat->qs_incoredqs,
-			sizeof(struct compat_fs_quota_stat) -
-			offsetof(struct compat_fs_quota_stat, qs_incoredqs)) ||
-			get_user(xdata, &fsqstat->qs_iwarnlimit) ||
-			put_user(xdata, &compat_fsqstat->qs_iwarnlimit))
-			break;
-		ret = 0;
-		break;
-	default:
-		ret = kernel_quotactl(cmd, special, id, addr);
-	}
-	return ret;
-}
diff --git a/fs/quota/compat.h b/fs/quota/compat.h
new file mode 100644
index 00000000000000..ef7d1e12d650b3
--- /dev/null
+++ b/fs/quota/compat.h
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/compat.h>
+
+struct compat_if_dqblk {
+	compat_u64			dqb_bhardlimit;
+	compat_u64			dqb_bsoftlimit;
+	compat_u64			dqb_curspace;
+	compat_u64			dqb_ihardlimit;
+	compat_u64			dqb_isoftlimit;
+	compat_u64			dqb_curinodes;
+	compat_u64			dqb_btime;
+	compat_u64			dqb_itime;
+	compat_uint_t			dqb_valid;
+};
+
+struct compat_fs_qfilestat {
+	compat_u64			dqb_bhardlimit;
+	compat_u64			qfs_nblks;
+	compat_uint_t			qfs_nextents;
+};
+
+struct compat_fs_quota_stat {
+	__s8				qs_version;
+	__u16				qs_flags;
+	__s8				qs_pad;
+	struct compat_fs_qfilestat	qs_uquota;
+	struct compat_fs_qfilestat	qs_gquota;
+	compat_uint_t			qs_incoredqs;
+	compat_int_t			qs_btimelimit;
+	compat_int_t			qs_itimelimit;
+	compat_int_t			qs_rtbtimelimit;
+	__u16				qs_bwarnlimit;
+	__u16				qs_iwarnlimit;
+};
diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 5444d3c4d93f37..e1e9d05a14c3e4 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -19,6 +19,7 @@
 #include <linux/types.h>
 #include <linux/writeback.h>
 #include <linux/nospec.h>
+#include "compat.h"
 
 static int check_quotactl_permission(struct super_block *sb, int type, int cmd,
 				     qid_t id)
@@ -211,8 +212,18 @@ static int quota_getquota(struct super_block *sb, int type, qid_t id,
 	if (ret)
 		return ret;
 	copy_to_if_dqblk(&idq, &fdq);
-	if (copy_to_user(addr, &idq, sizeof(idq)))
-		return -EFAULT;
+
+	if (compat_need_64bit_alignment_fixup()) {
+		struct compat_if_dqblk __user *compat_dqblk = addr;
+
+		if (copy_to_user(compat_dqblk, &idq, sizeof(*compat_dqblk)))
+			return -EFAULT;
+		if (put_user(idq.dqb_valid, &compat_dqblk->dqb_valid))
+			return -EFAULT;
+	} else {
+		if (copy_to_user(addr, &idq, sizeof(idq)))
+			return -EFAULT;
+	}
 	return 0;
 }
 
@@ -277,8 +288,16 @@ static int quota_setquota(struct super_block *sb, int type, qid_t id,
 	struct if_dqblk idq;
 	struct kqid qid;
 
-	if (copy_from_user(&idq, addr, sizeof(idq)))
-		return -EFAULT;
+	if (compat_need_64bit_alignment_fixup()) {
+		struct compat_if_dqblk __user *compat_dqblk = addr;
+
+		if (copy_from_user(&idq, compat_dqblk, sizeof(*compat_dqblk)) ||
+		    get_user(idq.dqb_valid, &compat_dqblk->dqb_valid))
+			return -EFAULT;
+	} else {
+		if (copy_from_user(&idq, addr, sizeof(idq)))
+			return -EFAULT;
+	}
 	if (!sb->s_qcop->set_dqblk)
 		return -ENOSYS;
 	qid = make_kqid(current_user_ns(), type, id);
@@ -382,6 +401,33 @@ static int quota_getstate(struct super_block *sb, int type,
 	return 0;
 }
 
+static int compat_copy_fs_qfilestat(struct compat_fs_qfilestat __user *to,
+		struct fs_qfilestat *from)
+{
+	if (copy_to_user(to, from, sizeof(*to)) ||
+	    put_user(from->qfs_nextents, &to->qfs_nextents))
+		return -EFAULT;
+	return 0;
+}
+
+static int compat_copy_fs_quota_stat(struct compat_fs_quota_stat __user *to,
+		struct fs_quota_stat *from)
+{
+	if (put_user(from->qs_version, &to->qs_version) ||
+	    put_user(from->qs_flags, &to->qs_flags) ||
+	    put_user(from->qs_pad, &to->qs_pad) ||
+	    compat_copy_fs_qfilestat(&to->qs_uquota, &from->qs_uquota) ||
+	    compat_copy_fs_qfilestat(&to->qs_gquota, &from->qs_gquota) ||
+	    put_user(from->qs_incoredqs, &to->qs_incoredqs) ||
+	    put_user(from->qs_btimelimit, &to->qs_btimelimit) ||
+	    put_user(from->qs_itimelimit, &to->qs_itimelimit) ||
+	    put_user(from->qs_rtbtimelimit, &to->qs_rtbtimelimit) ||
+	    put_user(from->qs_bwarnlimit, &to->qs_bwarnlimit) ||
+	    put_user(from->qs_iwarnlimit, &to->qs_iwarnlimit))
+		return -EFAULT;
+	return 0;
+}
+
 static int quota_getxstate(struct super_block *sb, int type, void __user *addr)
 {
 	struct fs_quota_stat fqs;
@@ -390,9 +436,14 @@ static int quota_getxstate(struct super_block *sb, int type, void __user *addr)
 	if (!sb->s_qcop->get_state)
 		return -ENOSYS;
 	ret = quota_getstate(sb, type, &fqs);
-	if (!ret && copy_to_user(addr, &fqs, sizeof(fqs)))
+	if (ret)
+		return ret;
+
+	if (compat_need_64bit_alignment_fixup())
+		return compat_copy_fs_quota_stat(addr, &fqs);
+	if (copy_to_user(addr, &fqs, sizeof(fqs)))
 		return -EFAULT;
-	return ret;
+	return 0;
 }
 
 static int quota_getstatev(struct super_block *sb, int type,
@@ -816,8 +867,8 @@ static struct super_block *quotactl_block(const char __user *special, int cmd)
  * calls. Maybe we need to add the process quotas etc. in the future,
  * but we probably should use rlimits for that.
  */
-int kernel_quotactl(unsigned int cmd, const char __user *special,
-		    qid_t id, void __user *addr)
+SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char __user *, special,
+		qid_t, id, void __user *, addr)
 {
 	uint cmds, type;
 	struct super_block *sb = NULL;
@@ -871,9 +922,3 @@ int kernel_quotactl(unsigned int cmd, const char __user *special,
 		path_put(pathp);
 	return ret;
 }
-
-SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char __user *, special,
-		qid_t, id, void __user *, addr)
-{
-	return kernel_quotactl(cmd, special, id, addr);
-}
diff --git a/include/linux/quotaops.h b/include/linux/quotaops.h
index 9cf0cd3dc88c68..a0f6668924d3ef 100644
--- a/include/linux/quotaops.h
+++ b/include/linux/quotaops.h
@@ -27,9 +27,6 @@ static inline bool is_quota_modification(struct inode *inode, struct iattr *ia)
 		(ia->ia_valid & ATTR_GID && !gid_eq(ia->ia_gid, inode->i_gid));
 }
 
-int kernel_quotactl(unsigned int cmd, const char __user *special,
-		    qid_t id, void __user *addr);
-
 #if defined(CONFIG_QUOTA)
 
 #define quota_error(sb, fmt, args...) \
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 3b69a560a7ac56..f01b91cc57fa00 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -370,7 +370,6 @@ COND_SYSCALL_COMPAT(fanotify_mark);
 /* x86 */
 COND_SYSCALL(vm86old);
 COND_SYSCALL(modify_ldt);
-COND_SYSCALL_COMPAT(quotactl32);
 COND_SYSCALL(vm86);
 COND_SYSCALL(kexec_file_load);
 
-- 
2.27.0


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Re: improve compat handling for the i386 u64 alignment quirk v2

[Ingo Molnar]

* Christoph Hellwig <hch@lst.de> wrote:

> Hi all,
> 
> the i386 ABI is a little special in that it uses less than natural
> alignment for 64-bit integer types (u64 and s64), and a significant
> amount of our compat handlers deals with just that.  Unfortunately
> there is no good way to check for this specific quirk at runtime,
> similar how in_compat_syscall() checks for a compat syscall.  This
> series adds such a check, and then uses the quota code as an example
> of how this improves the compat handling.  I have a few other places
> in mind where this will also be useful going forward.
> 
> Changes since v1:
>  - use asm-generic/compat.h instead of linux/compat.h for
>    compat_u64 and compat_s64
>  - fix a typo
> 
> Diffstat:
>  b/arch/arm64/include/asm/compat.h        |    2 
>  b/arch/mips/include/asm/compat.h         |    2 
>  b/arch/parisc/include/asm/compat.h       |    2 
>  b/arch/powerpc/include/asm/compat.h      |    2 
>  b/arch/s390/include/asm/compat.h         |    2 
>  b/arch/sparc/include/asm/compat.h        |    3 
>  b/arch/x86/entry/syscalls/syscall_32.tbl |    2 
>  b/arch/x86/include/asm/compat.h          |    3 
>  b/fs/quota/Kconfig                       |    5 -
>  b/fs/quota/Makefile                      |    1 
>  b/fs/quota/compat.h                      |   34 ++++++++
>  b/fs/quota/quota.c                       |   73 +++++++++++++++---
>  b/include/asm-generic/compat.h           |    8 ++
>  b/include/linux/compat.h                 |    9 ++
>  b/include/linux/quotaops.h               |    3 
>  b/kernel/sys_ni.c                        |    1 
>  fs/quota/compat.c                        |  120 -------------------------------
>  17 files changed, 113 insertions(+), 159 deletions(-)

If nobody objects to this being done at runtime, and if it's 100% ABI 
compatible, then the x86 impact looks good to me:

Acked-by: Ingo Molnar <mingo@kernel.org>

Thanks,

	Ingo

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RE: [PATCH 3/3] quota: simplify the quotactl compat handling

[David Laight]

From: Christoph Hellwig
> Sent: 31 July 2020 13:22
>
> Fold the misaligned u64 workarounds into the main quotactl flow instead
> of implementing a separate compat syscall handler.
> 
...
> diff --git a/fs/quota/compat.h b/fs/quota/compat.h
> new file mode 100644
> index 00000000000000..ef7d1e12d650b3
> --- /dev/null
> +++ b/fs/quota/compat.h
> @@ -0,0 +1,34 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/compat.h>
> +
> +struct compat_if_dqblk {
> +	compat_u64			dqb_bhardlimit;
> +	compat_u64			dqb_bsoftlimit;
> +	compat_u64			dqb_curspace;
> +	compat_u64			dqb_ihardlimit;
> +	compat_u64			dqb_isoftlimit;
> +	compat_u64			dqb_curinodes;
> +	compat_u64			dqb_btime;
> +	compat_u64			dqb_itime;
> +	compat_uint_t			dqb_valid;
> +};
> +
> +struct compat_fs_qfilestat {
> +	compat_u64			dqb_bhardlimit;
> +	compat_u64			qfs_nblks;
> +	compat_uint_t			qfs_nextents;
> +};
> +
> +struct compat_fs_quota_stat {
> +	__s8				qs_version;
> +	__u16				qs_flags;
> +	__s8				qs_pad;
> +	struct compat_fs_qfilestat	qs_uquota;
> +	struct compat_fs_qfilestat	qs_gquota;
> +	compat_uint_t			qs_incoredqs;
> +	compat_int_t			qs_btimelimit;
> +	compat_int_t			qs_itimelimit;
> +	compat_int_t			qs_rtbtimelimit;
> +	__u16				qs_bwarnlimit;
> +	__u16				qs_iwarnlimit;
> +};
> diff --git a/fs/quota/quota.c b/fs/quota/quota.c
> index 5444d3c4d93f37..e1e9d05a14c3e4 100644
> --- a/fs/quota/quota.c
> +++ b/fs/quota/quota.c
> @@ -19,6 +19,7 @@
>  #include <linux/types.h>
>  #include <linux/writeback.h>
>  #include <linux/nospec.h>
> +#include "compat.h"
> 
>  static int check_quotactl_permission(struct super_block *sb, int type, int cmd,
>  				     qid_t id)
> @@ -211,8 +212,18 @@ static int quota_getquota(struct super_block *sb, int type, qid_t id,
>  	if (ret)
>  		return ret;
>  	copy_to_if_dqblk(&idq, &fdq);
> -	if (copy_to_user(addr, &idq, sizeof(idq)))
> -		return -EFAULT;
> +
> +	if (compat_need_64bit_alignment_fixup()) {
> +		struct compat_if_dqblk __user *compat_dqblk = addr;
> +
> +		if (copy_to_user(compat_dqblk, &idq, sizeof(*compat_dqblk)))
> +			return -EFAULT;
> +		if (put_user(idq.dqb_valid, &compat_dqblk->dqb_valid))
> +			return -EFAULT;

Isn't this always copying the same value again?
I don't think Linux has any 64 bit systems with a 32bit compat
layer that have 64bit 'int'.
Since the only difference in the structures is the 'end padding'
isn't it enough to just copy the size of the 'compat' structure
in a compat system call?
It might even be that gcc will optimise the condition away
when the structure sizes match.

The same is true for a lot of the rest of this file.

	David

-
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Registration No: 1397386 (Wales)


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RE: [PATCH 3/3] quota: simplify the quotactl compat handling

[David Laight]

From: Christoph Hellwig
> Sent: 31 July 2020 13:22
> 
> Fold the misaligned u64 workarounds into the main quotactl flow instead
> of implementing a separate compat syscall handler.
> 
...
> +static int compat_copy_fs_quota_stat(struct compat_fs_quota_stat __user *to,
> +		struct fs_quota_stat *from)
> +{
> +	if (put_user(from->qs_version, &to->qs_version) ||
> +	    put_user(from->qs_flags, &to->qs_flags) ||
> +	    put_user(from->qs_pad, &to->qs_pad) ||
> +	    compat_copy_fs_qfilestat(&to->qs_uquota, &from->qs_uquota) ||
> +	    compat_copy_fs_qfilestat(&to->qs_gquota, &from->qs_gquota) ||
> +	    put_user(from->qs_incoredqs, &to->qs_incoredqs) ||
> +	    put_user(from->qs_btimelimit, &to->qs_btimelimit) ||
> +	    put_user(from->qs_itimelimit, &to->qs_itimelimit) ||
> +	    put_user(from->qs_rtbtimelimit, &to->qs_rtbtimelimit) ||
> +	    put_user(from->qs_bwarnlimit, &to->qs_bwarnlimit) ||
> +	    put_user(from->qs_iwarnlimit, &to->qs_iwarnlimit))
> +		return -EFAULT;
> +	return 0;
> +}

That might look better as a 'noinline' function that copied
all the fields into an on-stack struct compat_fs_quota_stat
and then did a single copy_to_user().

(I do 'like' qs_pad - I wonder what the person who added
it was smoking.)

	David

-
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[PATCH 3/3] quota: simplify the quotactl compat handling

[Christoph Hellwig]

Fold the misaligned u64 workarounds into the main quotactl flow instead
of implementing a separate compat syscall handler.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jan Kara <jack@suse.cz>
---
 arch/x86/entry/syscalls/syscall_32.tbl |   2 +-
 fs/quota/Kconfig                       |   5 --
 fs/quota/Makefile                      |   1 -
 fs/quota/compat.c                      | 120 -------------------------
 fs/quota/compat.h                      |  34 +++++++
 fs/quota/quota.c                       |  73 ++++++++++++---
 include/linux/quotaops.h               |   3 -
 kernel/sys_ni.c                        |   1 -
 8 files changed, 94 insertions(+), 145 deletions(-)
 delete mode 100644 fs/quota/compat.c
 create mode 100644 fs/quota/compat.h

diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 9d11028736661b..3db3d8823dc899 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -142,7 +142,7 @@
 128	i386	init_module		sys_init_module
 129	i386	delete_module		sys_delete_module
 130	i386	get_kernel_syms
-131	i386	quotactl		sys_quotactl			compat_sys_quotactl32
+131	i386	quotactl		sys_quotactl
 132	i386	getpgid			sys_getpgid
 133	i386	fchdir			sys_fchdir
 134	i386	bdflush			sys_bdflush
diff --git a/fs/quota/Kconfig b/fs/quota/Kconfig
index d1ceb76adb71e7..b59cd172b5f97c 100644
--- a/fs/quota/Kconfig
+++ b/fs/quota/Kconfig
@@ -70,8 +70,3 @@ config QFMT_V2
 config QUOTACTL
 	bool
 	default n
-
-config QUOTACTL_COMPAT
-	bool
-	depends on QUOTACTL && COMPAT_FOR_U64_ALIGNMENT
-	default y
diff --git a/fs/quota/Makefile b/fs/quota/Makefile
index f2b49d0f0287c9..9160639daffa75 100644
--- a/fs/quota/Makefile
+++ b/fs/quota/Makefile
@@ -4,5 +4,4 @@ obj-$(CONFIG_QFMT_V1)		+= quota_v1.o
 obj-$(CONFIG_QFMT_V2)		+= quota_v2.o
 obj-$(CONFIG_QUOTA_TREE)	+= quota_tree.o
 obj-$(CONFIG_QUOTACTL)		+= quota.o kqid.o
-obj-$(CONFIG_QUOTACTL_COMPAT)	+= compat.o
 obj-$(CONFIG_QUOTA_NETLINK_INTERFACE)	+= netlink.o
diff --git a/fs/quota/compat.c b/fs/quota/compat.c
deleted file mode 100644
index c305728576193d..00000000000000
--- a/fs/quota/compat.c
+++ /dev/null
@@ -1,120 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-
-#include <linux/syscalls.h>
-#include <linux/compat.h>
-#include <linux/quotaops.h>
-
-/*
- * This code works only for 32 bit quota tools over 64 bit OS (x86_64, ia64)
- * and is necessary due to alignment problems.
- */
-struct compat_if_dqblk {
-	compat_u64 dqb_bhardlimit;
-	compat_u64 dqb_bsoftlimit;
-	compat_u64 dqb_curspace;
-	compat_u64 dqb_ihardlimit;
-	compat_u64 dqb_isoftlimit;
-	compat_u64 dqb_curinodes;
-	compat_u64 dqb_btime;
-	compat_u64 dqb_itime;
-	compat_uint_t dqb_valid;
-};
-
-/* XFS structures */
-struct compat_fs_qfilestat {
-	compat_u64 dqb_bhardlimit;
-	compat_u64 qfs_nblks;
-	compat_uint_t qfs_nextents;
-};
-
-struct compat_fs_quota_stat {
-	__s8		qs_version;
-	__u16		qs_flags;
-	__s8		qs_pad;
-	struct compat_fs_qfilestat	qs_uquota;
-	struct compat_fs_qfilestat	qs_gquota;
-	compat_uint_t	qs_incoredqs;
-	compat_int_t	qs_btimelimit;
-	compat_int_t	qs_itimelimit;
-	compat_int_t	qs_rtbtimelimit;
-	__u16		qs_bwarnlimit;
-	__u16		qs_iwarnlimit;
-};
-
-COMPAT_SYSCALL_DEFINE4(quotactl32, unsigned int, cmd,
-		       const char __user *, special, qid_t, id,
-		       void __user *, addr)
-{
-	unsigned int cmds;
-	struct if_dqblk __user *dqblk;
-	struct compat_if_dqblk __user *compat_dqblk;
-	struct fs_quota_stat __user *fsqstat;
-	struct compat_fs_quota_stat __user *compat_fsqstat;
-	compat_uint_t data;
-	u16 xdata;
-	long ret;
-
-	cmds = cmd >> SUBCMDSHIFT;
-
-	switch (cmds) {
-	case Q_GETQUOTA:
-		dqblk = compat_alloc_user_space(sizeof(struct if_dqblk));
-		compat_dqblk = addr;
-		ret = kernel_quotactl(cmd, special, id, dqblk);
-		if (ret)
-			break;
-		if (copy_in_user(compat_dqblk, dqblk, sizeof(*compat_dqblk)) ||
-			get_user(data, &dqblk->dqb_valid) ||
-			put_user(data, &compat_dqblk->dqb_valid))
-			ret = -EFAULT;
-		break;
-	case Q_SETQUOTA:
-		dqblk = compat_alloc_user_space(sizeof(struct if_dqblk));
-		compat_dqblk = addr;
-		ret = -EFAULT;
-		if (copy_in_user(dqblk, compat_dqblk, sizeof(*compat_dqblk)) ||
-			get_user(data, &compat_dqblk->dqb_valid) ||
-			put_user(data, &dqblk->dqb_valid))
-			break;
-		ret = kernel_quotactl(cmd, special, id, dqblk);
-		break;
-	case Q_XGETQSTAT:
-		fsqstat = compat_alloc_user_space(sizeof(struct fs_quota_stat));
-		compat_fsqstat = addr;
-		ret = kernel_quotactl(cmd, special, id, fsqstat);
-		if (ret)
-			break;
-		ret = -EFAULT;
-		/* Copying qs_version, qs_flags, qs_pad */
-		if (copy_in_user(compat_fsqstat, fsqstat,
-			offsetof(struct compat_fs_quota_stat, qs_uquota)))
-			break;
-		/* Copying qs_uquota */
-		if (copy_in_user(&compat_fsqstat->qs_uquota,
-			&fsqstat->qs_uquota,
-			sizeof(compat_fsqstat->qs_uquota)) ||
-			get_user(data, &fsqstat->qs_uquota.qfs_nextents) ||
-			put_user(data, &compat_fsqstat->qs_uquota.qfs_nextents))
-			break;
-		/* Copying qs_gquota */
-		if (copy_in_user(&compat_fsqstat->qs_gquota,
-			&fsqstat->qs_gquota,
-			sizeof(compat_fsqstat->qs_gquota)) ||
-			get_user(data, &fsqstat->qs_gquota.qfs_nextents) ||
-			put_user(data, &compat_fsqstat->qs_gquota.qfs_nextents))
-			break;
-		/* Copying the rest */
-		if (copy_in_user(&compat_fsqstat->qs_incoredqs,
-			&fsqstat->qs_incoredqs,
-			sizeof(struct compat_fs_quota_stat) -
-			offsetof(struct compat_fs_quota_stat, qs_incoredqs)) ||
-			get_user(xdata, &fsqstat->qs_iwarnlimit) ||
-			put_user(xdata, &compat_fsqstat->qs_iwarnlimit))
-			break;
-		ret = 0;
-		break;
-	default:
-		ret = kernel_quotactl(cmd, special, id, addr);
-	}
-	return ret;
-}
diff --git a/fs/quota/compat.h b/fs/quota/compat.h
new file mode 100644
index 00000000000000..ef7d1e12d650b3
--- /dev/null
+++ b/fs/quota/compat.h
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/compat.h>
+
+struct compat_if_dqblk {
+	compat_u64			dqb_bhardlimit;
+	compat_u64			dqb_bsoftlimit;
+	compat_u64			dqb_curspace;
+	compat_u64			dqb_ihardlimit;
+	compat_u64			dqb_isoftlimit;
+	compat_u64			dqb_curinodes;
+	compat_u64			dqb_btime;
+	compat_u64			dqb_itime;
+	compat_uint_t			dqb_valid;
+};
+
+struct compat_fs_qfilestat {
+	compat_u64			dqb_bhardlimit;
+	compat_u64			qfs_nblks;
+	compat_uint_t			qfs_nextents;
+};
+
+struct compat_fs_quota_stat {
+	__s8				qs_version;
+	__u16				qs_flags;
+	__s8				qs_pad;
+	struct compat_fs_qfilestat	qs_uquota;
+	struct compat_fs_qfilestat	qs_gquota;
+	compat_uint_t			qs_incoredqs;
+	compat_int_t			qs_btimelimit;
+	compat_int_t			qs_itimelimit;
+	compat_int_t			qs_rtbtimelimit;
+	__u16				qs_bwarnlimit;
+	__u16				qs_iwarnlimit;
+};
diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 47f9e151988b3e..6b37d58f1067d4 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -19,6 +19,7 @@
 #include <linux/types.h>
 #include <linux/writeback.h>
 #include <linux/nospec.h>
+#include "compat.h"
 
 static int check_quotactl_permission(struct super_block *sb, int type, int cmd,
 				     qid_t id)
@@ -211,8 +212,18 @@ static int quota_getquota(struct super_block *sb, int type, qid_t id,
 	if (ret)
 		return ret;
 	copy_to_if_dqblk(&idq, &fdq);
-	if (copy_to_user(addr, &idq, sizeof(idq)))
-		return -EFAULT;
+
+	if (compat_need_64bit_alignment_fixup()) {
+		struct compat_if_dqblk __user *compat_dqblk = addr;
+
+		if (copy_to_user(compat_dqblk, &idq, sizeof(*compat_dqblk)))
+			return -EFAULT;
+		if (put_user(idq.dqb_valid, &compat_dqblk->dqb_valid))
+			return -EFAULT;
+	} else {
+		if (copy_to_user(addr, &idq, sizeof(idq)))
+			return -EFAULT;
+	}
 	return 0;
 }
 
@@ -277,8 +288,16 @@ static int quota_setquota(struct super_block *sb, int type, qid_t id,
 	struct if_dqblk idq;
 	struct kqid qid;
 
-	if (copy_from_user(&idq, addr, sizeof(idq)))
-		return -EFAULT;
+	if (compat_need_64bit_alignment_fixup()) {
+		struct compat_if_dqblk __user *compat_dqblk = addr;
+
+		if (copy_from_user(&idq, compat_dqblk, sizeof(*compat_dqblk)) ||
+		    get_user(idq.dqb_valid, &compat_dqblk->dqb_valid))
+			return -EFAULT;
+	} else {
+		if (copy_from_user(&idq, addr, sizeof(idq)))
+			return -EFAULT;
+	}
 	if (!sb->s_qcop->set_dqblk)
 		return -ENOSYS;
 	qid = make_kqid(current_user_ns(), type, id);
@@ -382,6 +401,33 @@ static int quota_getstate(struct super_block *sb, int type,
 	return 0;
 }
 
+static int compat_copy_fs_qfilestat(struct compat_fs_qfilestat __user *to,
+		struct fs_qfilestat *from)
+{
+	if (copy_to_user(to, from, sizeof(*to)) ||
+	    put_user(from->qfs_nextents, &to->qfs_nextents))
+		return -EFAULT;
+	return 0;
+}
+
+static int compat_copy_fs_quota_stat(struct compat_fs_quota_stat __user *to,
+		struct fs_quota_stat *from)
+{
+	if (put_user(from->qs_version, &to->qs_version) ||
+	    put_user(from->qs_flags, &to->qs_flags) ||
+	    put_user(from->qs_pad, &to->qs_pad) ||
+	    compat_copy_fs_qfilestat(&to->qs_uquota, &from->qs_uquota) ||
+	    compat_copy_fs_qfilestat(&to->qs_gquota, &from->qs_gquota) ||
+	    put_user(from->qs_incoredqs, &to->qs_incoredqs) ||
+	    put_user(from->qs_btimelimit, &to->qs_btimelimit) ||
+	    put_user(from->qs_itimelimit, &to->qs_itimelimit) ||
+	    put_user(from->qs_rtbtimelimit, &to->qs_rtbtimelimit) ||
+	    put_user(from->qs_bwarnlimit, &to->qs_bwarnlimit) ||
+	    put_user(from->qs_iwarnlimit, &to->qs_iwarnlimit))
+		return -EFAULT;
+	return 0;
+}
+
 static int quota_getxstate(struct super_block *sb, int type, void __user *addr)
 {
 	struct fs_quota_stat fqs;
@@ -390,9 +436,14 @@ static int quota_getxstate(struct super_block *sb, int type, void __user *addr)
 	if (!sb->s_qcop->get_state)
 		return -ENOSYS;
 	ret = quota_getstate(sb, type, &fqs);
-	if (!ret && copy_to_user(addr, &fqs, sizeof(fqs)))
+	if (ret)
+		return ret;
+
+	if (compat_need_64bit_alignment_fixup())
+		return compat_copy_fs_quota_stat(addr, &fqs);
+	if (copy_to_user(addr, &fqs, sizeof(fqs)))
 		return -EFAULT;
-	return ret;
+	return 0;
 }
 
 static int quota_getstatev(struct super_block *sb, int type,
@@ -816,8 +867,8 @@ static struct super_block *quotactl_block(const char __user *special, int cmd)
  * calls. Maybe we need to add the process quotas etc. in the future,
  * but we probably should use rlimits for that.
  */
-int kernel_quotactl(unsigned int cmd, const char __user *special,
-		    qid_t id, void __user *addr)
+SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char __user *, special,
+		qid_t, id, void __user *, addr)
 {
 	uint cmds, type;
 	struct super_block *sb = NULL;
@@ -871,9 +922,3 @@ int kernel_quotactl(unsigned int cmd, const char __user *special,
 		path_put(pathp);
 	return ret;
 }
-
-SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char __user *, special,
-		qid_t, id, void __user *, addr)
-{
-	return kernel_quotactl(cmd, special, id, addr);
-}
diff --git a/include/linux/quotaops.h b/include/linux/quotaops.h
index 9cf0cd3dc88c68..a0f6668924d3ef 100644
--- a/include/linux/quotaops.h
+++ b/include/linux/quotaops.h
@@ -27,9 +27,6 @@ static inline bool is_quota_modification(struct inode *inode, struct iattr *ia)
 		(ia->ia_valid & ATTR_GID && !gid_eq(ia->ia_gid, inode->i_gid));
 }
 
-int kernel_quotactl(unsigned int cmd, const char __user *special,
-		    qid_t id, void __user *addr);
-
 #if defined(CONFIG_QUOTA)
 
 #define quota_error(sb, fmt, args...) \
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 4d59775ea79c1e..c925d1e1777efc 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -369,7 +369,6 @@ COND_SYSCALL_COMPAT(fanotify_mark);
 /* x86 */
 COND_SYSCALL(vm86old);
 COND_SYSCALL(modify_ldt);
-COND_SYSCALL_COMPAT(quotactl32);
 COND_SYSCALL(vm86);
 COND_SYSCALL(kexec_file_load);
 
-- 
2.28.0


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