kernel/linux.git/fs/fuse, branch v6.1.187

fuse: fix invalidate lock leak on open O_TRUNC DAX failure

2026-09-02T12:28:35+00:00

commit a927f1867e61b78f39f9da0bbba3c98c2ca151fe upstream. fuse_open() takes filemap_invalidate_lock() for a DAX truncate (dax_truncate = true) and releases it before the out_inode_unlock label. But when fuse_dax_break_layouts() fails, the goto out_inode_unlock skips the unlock and leaks the rwsem, so any later fault or truncate on the file stalls on the stale lock. fuse_dax_break_layouts() can fail with -ERESTARTSYS when a signal interrupts the wait for busy DAX pages to drain: open("file", O_RDWR | O_TRUNC) └─ fuse_open() ├─ filemap_invalidate_lock() # dax_truncate └─ fuse_dax_break_layouts() └─ dax_break_layout() └─ wait_page_idle() # TASK_INTERRUPTIBLE └─ fuse_wait_dax_page() # unlock, schedule, re-lock └─ signal → -ERESTARTSYS goto out_inode_unlock # <- lock leaked Fix this by moving filemap_invalidate_unlock() below the label so that all error paths release the lock, and rename the label to out_unlock as it now covers more than just the inode lock. Fixes: 2fdbb8dd0155 ("fuse: fix deadlock between atomic O_TRUNC and page invalidation") Cc: stable@vger.kernel.org # v6.0+ Signed-off-by: Baokun Li Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman

fuse: fix invalidate lock leak on setattr writeback failure

2026-09-02T12:28:35+00:00

commit 9afeca0d569c9fc89d758fe7a9339d1e8afb1546 upstream. fuse_do_setattr() takes filemap_invalidate_lock() for a DAX truncate (fault_blocked = true) and releases it at the out:/error: labels. But when a writeback flush is also needed, a write_inode_now() failure returns directly and leaks the lock, so any later fault or truncate on the file stalls on the stale rwsem. For example, truncate(2) on a setuid file reaches fuse_do_setattr() with both ATTR_SIZE and ATTR_MODE set: truncate(2) └─ do_truncate() ├─ dentry_needs_remove_privs() # S_ISUID └─ notify_change() # KILL_SUID -> ATTR_MODE └─ fuse_setattr() # no killpriv: │ # ia_valid |= ATTR_MODE └─ fuse_do_setattr() ├─ filemap_invalidate_lock() # IS_DAX && is_truncate └─ write_inode_now() # is_wb && ATTR_MODE └─ if (err) # e.g. daemon -> -EIO return err # <- lock leaked Fix this by adding an unlock label that releases the lock before returning the error, and use it for the fuse_dax_break_layouts() failure path as well. Fixes: 6ae330cad6ef ("virtiofs: serialize truncate/punch_hole and dax fault path") Cc: stable@vger.kernel.org # v5.10+ Signed-off-by: Baokun Li Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman

fuse: re-lock request before returning from fuse_ref_folio()

2026-07-24T13:54:30+00:00

commit b5befa80fdbe287a98480effed9564712924add5 upstream. fuse_ref_folio() unlocks the request but does not re-lock it before returning. fuse_chan_abort() can end the request and the async end callback (eg fuse_writepage_free()) can free the args while the subsequent copy chain logic after fuse_ref_folio() accesses them, leading to use-after-free issues. Fix this by locking the request in fuse_ref_folio() before returning. Fixes: c3021629a0d8 ("fuse: support splice() reading from fuse device") Cc: stable@vger.kernel.org Signed-off-by: Joanne Koong Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman

fuse: fix device node leak in cuse_process_init_reply()

2026-07-24T13:54:30+00:00

commit 9fa4f7a53406430ee9982f2f636a15b338185122 upstream. If device_add() succeeds during CUSE initialization but a subsequent step (cdev_alloc() or cdev_add()) fails, the error path calls put_device() without first calling device_del(). This leaks the devtmpfs entry created by device_add(), leaving a stale /dev/ node that persists until reboot. Since the cuse_conn is never linked into cuse_conntbl on the failure path, cuse_channel_release() sees cc->dev == NULL and skips device_unregister(), so no other code path cleans up the node. This has several consequences: - The device name is permanently poisoned: any subsequent attempt to create a CUSE device with the same name hits the stale sysfs entry, device_add() fails, and the new device is aborted. - The collision manifests as ENODEV returned to userspace with no dmesg diagnostic, making it very difficult to debug. - The failure is self-perpetuating: once a name is leaked, all future attempts with that name fail identically. Fix this by introducing an err_dev label that calls device_del() to undo device_add() before falling through to err_unlock. The existing err_unlock path from a device_add() failure correctly skips device_del() since the device was never added. Testing instructions can be found at the lore link below. Link: https://lore.kernel.org/all/20260408-wip-cuse-leak-fix-v1-0-1c028d575e97@redhat.com/ Signed-off-by: Alberto Ruiz Fixes: 151060ac1314 ("CUSE: implement CUSE - Character device in Userspace") Cc: stable@vger.kernel.org Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman

fuse: re-lock request before replacing page cache folio

2026-07-04T11:41:33+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

virtiofs: fix UAF on submount umount

2026-07-04T11:41:29+00:00

commit 06b41351779e9289e8785694ade9042ae85e41ea upstream. iput() called from fuse_release_end() can Oops if the super block has already been destroyed. Normally this is prevented by waiting for num_waiting to go down to zero before commencing with super block shutdown. This only works, however, for the last submount instance, as the wait counter is per connection, not per superblock. Revert to using synchronous release requests for the auto_submounts case, which is virtiofs only at this time. Reported-by: Aurélien Bombo Reported-by: Zhihao Cheng Cc: Greg Kurz Closes: https://github.com/kata-containers/kata-containers/issues/12589 Fixes: 26e5c67deb2e ("fuse: fix livelock in synchronous file put from fuseblk workers") Cc: stable@vger.kernel.org Reviewed-by: Greg Kurz Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman

fuse: limit FUSE_NOTIFY_RETRIEVE to uptodate folios

2026-07-04T11:41:26+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

2026-06-19T11:37:15+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: quiet down complaints in fuse_conn_limit_write

2026-06-01T15:38:42+00:00

commit 129a45f9755a89f573c6a513a6b9e3d234ce89b0 upstream. gcc 15 complains about an uninitialized variable val that is passed by reference into fuse_conn_limit_write: control.c: In function ‘fuse_conn_congestion_threshold_write’: include/asm-generic/rwonce.h:55:37: warning: ‘val’ may be used uninitialized [-Wmaybe-uninitialized] 55 | *(volatile typeof(x) *)&(x) = (val); \ | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~ include/asm-generic/rwonce.h:61:9: note: in expansion of macro ‘__WRITE_ONCE’ 61 | __WRITE_ONCE(x, val); \ | ^~~~~~~~~~~~ control.c:178:9: note: in expansion of macro ‘WRITE_ONCE’ 178 | WRITE_ONCE(fc->congestion_threshold, val); | ^~~~~~~~~~ control.c:166:18: note: ‘val’ was declared here 166 | unsigned val; | ^~~ Unfortunately there's enough macro spew involved in kstrtoul_from_user that I think gcc gives up on its analysis and sprays the above warning. AFAICT it's not actually a bug, but we could just zero-initialize the variable to enable using -Wmaybe-uninitialized to find real problems. Previously we would use some weird uninitialized_var annotation to quiet down the warnings, so clearly this code has been like this for quite some time. Cc: stable@vger.kernel.org # v5.9 Fixes: 3f649ab728cda8 ("treewide: Remove uninitialized_var() usage") Signed-off-by: Darrick J. Wong Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman

fuse: reject oversized dirents in page cache

2026-06-01T15:38:42+00:00

commit 51a8de6c50bf947c8f534cd73da4c8f0a13e7bed upstream. fuse_add_dirent_to_cache() computes a serialized dirent size from the server-controlled namelen field and copies the dirent into a single page-cache page. The existing logic only checks whether the dirent fits in the remaining space of the current page and advances to a fresh page if not. It never checks whether the dirent itself exceeds PAGE_SIZE. As a result, a malicious FUSE server can return a dirent with namelen=4095, producing a serialized record size of 4120 bytes. On 4 KiB page systems this causes memcpy() to overflow the cache page by 24 bytes into the following kernel page. Reject dirents that cannot fit in a single page before copying them into the readdir cache. Fixes: 69e34551152a ("fuse: allow caching readdir") Cc: stable@vger.kernel.org # v6.16+ Assisted-by: Bynario AI Signed-off-by: Samuel Page Reported-by: Qi Tang Reported-by: Zijun Hu Signed-off-by: Miklos Szeredi Link: https://patch.msgid.link/20260420090139.662772-1-mszeredi@redhat.com Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman