linux-stable.git/fs/fuse/dev.c, branch linux-5.15.y

fuse: re-lock request before replacing page cache folio

2026-07-04T11:39:41+00:00

[ Upstream commit a078484921052d0badd827fcc2770b5cfc1d4120 ]

fuse_try_move_folio() unlocks the request on entry but does not
re-lock it on the success path. This means fuse_chan_abort() can end the
request and free the fuse_io_args (eg fuse_readpages_end()) while the
subsequent copy chain logic after fuse_try_move_folio() accesses the
fuse_io_args, leading to use-after-free issues.

Fix this by calling lock_request() before replace_page_cache_folio().
This ensures the request is locked on the success path which will
prevent the fuse_io_args from being freed while the later copying logic
runs, and also ensures that the ap->folios[i]->mapping is never null
since ap->folios[i] will always point to the newfolio after
replace_page_cache_folio().

Fixes: ce534fb05292 ("fuse: allow splice to move pages")
Cc: stable@vger.kernel.org
Reported-by: Lei Lu 
Signed-off-by: Joanne Koong 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

fuse: limit FUSE_NOTIFY_RETRIEVE to uptodate folios

2026-07-04T11:39:36+00:00

[ Upstream commit 4e3d1b2c48ca6c55f1e9ca7f8dccc76f120f276c ]

FUSE_NOTIFY_RETRIEVE must be limited to uptodate folios; !uptodate folios
can contain uninitialized data.
Since FUSE_NOTIFY_RETRIEVE is intended to only return data that is already
in the page cache and not wait for data from the FUSE daemon, treat
!uptodate folios as if they weren't present.

This only has security impact on systems that don't enable automatic
zero-initialization of all page allocations via
CONFIG_INIT_ON_ALLOC_DEFAULT_ON or init_on_alloc=1.

Cc: stable@kernel.org
Fixes: 2d45ba381a74 ("fuse: add retrieve request")
Signed-off-by: Jann Horn 
Link: https://patch.msgid.link/20260519-fuse-retrieve-uptodate-v1-1-a7a1912a37f9@google.com
Acked-by: Miklos Szeredi 
Signed-off-by: Christian Brauner (Amutable) 
[adjusted for stable: page instead of folio]
Signed-off-by: Jann Horn 
Signed-off-by: Sasha Levin

fuse: reject fuse_notify() pagecache ops on directories

2026-06-19T11:33:37+00:00

commit 9c954499d43aefac01c5dfb57a82b13d2dcf4b94 upstream.

The operations FUSE_NOTIFY_STORE and FUSE_NOTIFY_RETRIEVE allow the
FUSE daemon to actively write/read pagecache contents.

For directories with FOPEN_CACHE_DIR, the pagecache is used as
kernel-internal cache storage, and userspace is not supposed to have
direct access to this cache - in particular, fuse_parse_cache() will hit
WARN_ON() if the cache contains bogus data.

Reject FUSE_NOTIFY_STORE and FUSE_NOTIFY_RETRIEVE on anything other than
regular files with -EINVAL.

Fixes: 5d7bc7e8680c ("fuse: allow using readdir cache")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn 
Link: https://patch.msgid.link/20260519-fuse-dir-pagecache-v2-1-5428fa48e175@google.com
Acked-by: Miklos Szeredi 
Signed-off-by: Christian Brauner (Amutable) 
Signed-off-by: Greg Kroah-Hartman

fuse: Initialize beyond-EOF page contents before setting uptodate

2024-09-04T11:23:14+00:00

commit 3c0da3d163eb32f1f91891efaade027fa9b245b9 upstream.

fuse_notify_store(), unlike fuse_do_readpage(), does not enable page
zeroing (because it can be used to change partial page contents).

So fuse_notify_store() must be more careful to fully initialize page
contents (including parts of the page that are beyond end-of-file)
before marking the page uptodate.

The current code can leave beyond-EOF page contents uninitialized, which
makes these uninitialized page contents visible to userspace via mmap().

This is an information leak, but only affects systems which do not
enable init-on-alloc (via CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y or the
corresponding kernel command line parameter).

Link: https://bugs.chromium.org/p/project-zero/issues/detail?id=2574
Cc: stable@kernel.org
Fixes: a1d75f258230 ("fuse: add store request")
Signed-off-by: Jann Horn 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

fuse: fix pipe buffer lifetime for direct_io

2022-03-16T13:23:42+00:00

commit 0c4bcfdecb1ac0967619ee7ff44871d93c08c909 upstream.

In FOPEN_DIRECT_IO mode, fuse_file_write_iter() calls
fuse_direct_write_iter(), which normally calls fuse_direct_io(), which then
imports the write buffer with fuse_get_user_pages(), which uses
iov_iter_get_pages() to grab references to userspace pages instead of
actually copying memory.

On the filesystem device side, these pages can then either be read to
userspace (via fuse_dev_read()), or splice()d over into a pipe using
fuse_dev_splice_read() as pipe buffers with &nosteal_pipe_buf_ops.

This is wrong because after fuse_dev_do_read() unlocks the FUSE request,
the userspace filesystem can mark the request as completed, causing write()
to return. At that point, the userspace filesystem should no longer have
access to the pipe buffer.

Fix by copying pages coming from the user address space to new pipe
buffers.

Reported-by: Jann Horn 
Fixes: c3021629a0d8 ("fuse: support splice() reading from fuse device")
Cc: 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

fuse: release pipe buf after last use

2021-12-01T08:04:42+00:00

commit 473441720c8616dfaf4451f9c7ea14f0eb5e5d65 upstream.

Checking buf->flags should be done before the pipe_buf_release() is called
on the pipe buffer, since releasing the buffer might modify the flags.

This is exactly what page_cache_pipe_buf_release() does, and which results
in the same VM_BUG_ON_PAGE(PageLRU(page)) that the original patch was
trying to fix.

Reported-by: Justin Forbes 
Fixes: 712a951025c0 ("fuse: fix page stealing")
Cc:  # v2.6.35
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

fuse: fix page stealing

2021-11-18T18:15:56+00:00

commit 712a951025c0667ff00b25afc360f74e639dfabe upstream.

It is possible to trigger a crash by splicing anon pipe bufs to the fuse
device.

The reason for this is that anon_pipe_buf_release() will reuse buf->page if
the refcount is 1, but that page might have already been stolen and its
flags modified (e.g. PG_lru added).

This happens in the unlikely case of fuse_dev_splice_write() getting around
to calling pipe_buf_release() after a page has been stolen, added to the
page cache and removed from the page cache.

Fix by calling pipe_buf_release() right after the page was inserted into
the page cache.  In this case the page has an elevated refcount so any
release function will know that the page isn't reusable.

Reported-by: Frank Dinoff 
Link: https://lore.kernel.org/r/CAAmZXrsGg2xsP1CK+cbuEMumtrqdvD-NKnWzhNcvn71RV3c1yw@mail.gmail.com/
Fixes: dd3bb14f44a6 ("fuse: support splice() writing to fuse device")
Cc:  # v2.6.35
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

fuse: fix use after free in fuse_read_interrupt()

2021-08-04T11:22:58+00:00

There is a potential race between fuse_read_interrupt() and
fuse_request_end().

TASK1
  in fuse_read_interrupt(): delete req->intr_entry (while holding
  fiq->lock)

TASK2
  in fuse_request_end(): req->intr_entry is empty -> skip fiq->lock
  wake up TASK3

TASK3
  request is freed

TASK1
  in fuse_read_interrupt(): dereference req->in.h.unique ***BAM***


Fix by always grabbing fiq->lock if the request was ever interrupted
(FR_INTERRUPTED set) thereby serializing with concurrent
fuse_read_interrupt() calls.

FR_INTERRUPTED is set before the request is queued on fiq->interrupts.
Dequeing the request is done with list_del_init() but FR_INTERRUPTED is not
cleared in this case.

Reported-by: lijiazi 
Signed-off-by: Miklos Szeredi

virtiofs: Fix spelling mistakes

2021-06-22T07:15:36+00:00

Fix some spelling mistakes in comments:
refernce  ==> reference
happnes  ==> happens
threhold  ==> threshold
splitted  ==> split
mached  ==> matched

Signed-off-by: Zheng Yongjun 
Signed-off-by: Miklos Szeredi

fuse: reject internal errno

2021-06-22T07:15:35+00:00

Don't allow userspace to report errors that could be kernel-internal.

Reported-by: Anatoly Trosinenko 
Fixes: 334f485df85a ("[PATCH] FUSE - device functions")
Cc:  # v2.6.14
Signed-off-by: Miklos Szeredi