From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Kirill Smelkov <kirr@nexedi.com>,
Miklos Szeredi <mszeredi@redhat.com>
Subject: [PATCH 4.14 35/35] fuse: Add FOPEN_STREAM to use stream_open()
Date: Sun, 9 Jun 2019 18:42:41 +0200 [thread overview]
Message-ID: <20190609164127.532009984@linuxfoundation.org> (raw)
In-Reply-To: <20190609164125.377368385@linuxfoundation.org>
From: Kirill Smelkov <kirr@nexedi.com>
commit bbd84f33652f852ce5992d65db4d020aba21f882 upstream.
Starting from commit 9c225f2655e3 ("vfs: atomic f_pos accesses as per
POSIX") files opened even via nonseekable_open gate read and write via lock
and do not allow them to be run simultaneously. This can create read vs
write deadlock if a filesystem is trying to implement a socket-like file
which is intended to be simultaneously used for both read and write from
filesystem client. See commit 10dce8af3422 ("fs: stream_open - opener for
stream-like files so that read and write can run simultaneously without
deadlock") for details and e.g. commit 581d21a2d02a ("xenbus: fix deadlock
on writes to /proc/xen/xenbus") for a similar deadlock example on
/proc/xen/xenbus.
To avoid such deadlock it was tempting to adjust fuse_finish_open to use
stream_open instead of nonseekable_open on just FOPEN_NONSEEKABLE flags,
but grepping through Debian codesearch shows users of FOPEN_NONSEEKABLE,
and in particular GVFS which actually uses offset in its read and write
handlers
https://codesearch.debian.net/search?q=-%3Enonseekable+%3D
https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1080
https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1247-1346
https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1399-1481
so if we would do such a change it will break a real user.
Add another flag (FOPEN_STREAM) for filesystem servers to indicate that the
opened handler is having stream-like semantics; does not use file position
and thus the kernel is free to issue simultaneous read and write request on
opened file handle.
This patch together with stream_open() should be added to stable kernels
starting from v3.14+. This will allow to patch OSSPD and other FUSE
filesystems that provide stream-like files to return FOPEN_STREAM |
FOPEN_NONSEEKABLE in open handler and this way avoid the deadlock on all
kernel versions. This should work because fuse_finish_open ignores unknown
open flags returned from a filesystem and so passing FOPEN_STREAM to a
kernel that is not aware of this flag cannot hurt. In turn the kernel that
is not aware of FOPEN_STREAM will be < v3.14 where just FOPEN_NONSEEKABLE
is sufficient to implement streams without read vs write deadlock.
Cc: stable@vger.kernel.org # v3.14+
Signed-off-by: Kirill Smelkov <kirr@nexedi.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/fuse/file.c | 4 +++-
include/uapi/linux/fuse.h | 2 ++
2 files changed, 5 insertions(+), 1 deletion(-)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -178,7 +178,9 @@ void fuse_finish_open(struct inode *inod
file->f_op = &fuse_direct_io_file_operations;
if (!(ff->open_flags & FOPEN_KEEP_CACHE))
invalidate_inode_pages2(inode->i_mapping);
- if (ff->open_flags & FOPEN_NONSEEKABLE)
+ if (ff->open_flags & FOPEN_STREAM)
+ stream_open(inode, file);
+ else if (ff->open_flags & FOPEN_NONSEEKABLE)
nonseekable_open(inode, file);
if (fc->atomic_o_trunc && (file->f_flags & O_TRUNC)) {
struct fuse_inode *fi = get_fuse_inode(inode);
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -216,10 +216,12 @@ struct fuse_file_lock {
* FOPEN_DIRECT_IO: bypass page cache for this open file
* FOPEN_KEEP_CACHE: don't invalidate the data cache on open
* FOPEN_NONSEEKABLE: the file is not seekable
+ * FOPEN_STREAM: the file is stream-like (no file position at all)
*/
#define FOPEN_DIRECT_IO (1 << 0)
#define FOPEN_KEEP_CACHE (1 << 1)
#define FOPEN_NONSEEKABLE (1 << 2)
+#define FOPEN_STREAM (1 << 4)
/**
* INIT request/reply flags
next prev parent reply other threads:[~2019-06-09 17:17 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-09 16:42 [PATCH 4.14 00/35] 4.14.125-stable review Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 01/35] ethtool: fix potential userspace buffer overflow Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 02/35] Fix memory leak in sctp_process_init Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 03/35] neighbor: Call __ipv4_neigh_lookup_noref in neigh_xmit Greg Kroah-Hartman
2019-06-10 1:10 ` Nobuhiro Iwamatsu
2019-06-10 1:13 ` nobuhiro1.iwamatsu
2019-06-10 5:56 ` Greg KH
2019-06-09 16:42 ` [PATCH 4.14 04/35] net/mlx4_en: ethtool, Remove unsupported SFP EEPROM high pages query Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 05/35] net: rds: fix memory leak in rds_ib_flush_mr_pool Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 06/35] pktgen: do not sleep with the thread lock held Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 07/35] ipv6: fix EFAULT on sendto with icmpv6 and hdrincl Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 08/35] ipv6: use READ_ONCE() for inet->hdrincl as in ipv4 Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 09/35] net: sfp: read eeprom in maximum 16 byte increments Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 10/35] ipv6: fix the check before getting the cookie in rt6_get_cookie Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 11/35] Revert "fib_rules: fix error in backport of e9919a24d302 ("fib_rules: return 0...")" Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 12/35] Revert "fib_rules: return 0 directly if an exactly same rule exists when NLM_F_EXCL not supplied" Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 13/35] rcu: locking and unlocking need to always be at least barriers Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 14/35] parisc: Use implicit space register selection for loading the coherence index of I/O pdirs Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 15/35] fuse: fallocate: fix return with locked inode Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 16/35] pstore: Remove needless lock during console writes Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 17/35] pstore: Convert buf_lock to semaphore Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 18/35] pstore/ram: Run without kernel crash dump region Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 19/35] x86/power: Fix nosmt vs hibernation triple fault during resume Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 20/35] i2c: xiic: Add max_read_len quirk Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 21/35] MIPS: Bounds check virt_addr_valid Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 22/35] MIPS: pistachio: Build uImage.gz by default Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 23/35] Revert "MIPS: perf: ath79: Fix perfcount IRQ assignment" Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 24/35] genwqe: Prevent an integer overflow in the ioctl Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 25/35] test_firmware: Use correct snprintf() limit Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 26/35] drm/gma500/cdv: Check vbt config bits when detecting lvds panels Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 27/35] drm/nouveau: add kconfig option to turn off nouveau legacy contexts. (v3) Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 28/35] drm/amdgpu/psp: move psp version specific function pointers to early_init Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 29/35] drm/radeon: prefer lower reference dividers Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 30/35] drm/i915: Fix I915_EXEC_RING_MASK Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 31/35] drm/i915/fbc: disable framebuffer compression on GeminiLake Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 32/35] TTY: serial_core, add ->install Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 33/35] qmi_wwan: Add quirk for Quectel dynamic config Greg Kroah-Hartman
2019-06-09 16:42 ` [PATCH 4.14 34/35] fs: stream_open - opener for stream-like files so that read and write can run simultaneously without deadlock Greg Kroah-Hartman
2019-06-09 16:42 ` Greg Kroah-Hartman [this message]
2019-06-10 7:27 ` [PATCH 4.14 00/35] 4.14.125-stable review Naresh Kamboju
2019-06-10 8:50 ` Jon Hunter
2019-06-10 14:43 ` Guenter Roeck
2019-06-10 21:56 ` shuah
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