kernel/git/stable/linux-stable.git/fs/fuse, branch linux-6.6.y

fuse: check for NULL root inode in fuse_fill_super_submount

2026-09-14T11:29:52+00:00

[ Upstream commit 928f659a3e3650978a5b4829cc982324f72b474b ] fuse_iget() can return NULL when its inode allocation fails, but fuse_fill_super_submount() passed the result straight to get_fuse_inode() and decremented fi->nlookup without checking it: root = fuse_iget(sb, parent_fi->nodeid, ...); fi = get_fuse_inode(root); fi->nlookup--; Inside fuse_iget() the inode allocation can fail and return NULL. The submount root takes the iget5_locked() path, whose alloc_inode() can fail under memory pressure (the auto-submount branch can fail the same way in new_inode() or fuse_alloc_submount_lookup()): inode = iget5_locked(sb, nodeid, fuse_inode_eq, fuse_inode_set, &nodeid); if (!inode) return NULL; A NULL root makes get_fuse_inode() a container_of() on NULL and the nlookup decrement a write to a bogus address, oopsing the mount. With CONFIG_KASAN the following null pointer dereference is reported when the root inode allocation of an auto-submount fails (e.g. under memory pressure): ================================================================== BUG: KASAN: null-ptr-deref in fuse_get_tree_submount+0x656/0x8b0 Read of size 8 at addr 00000000000002b0 by task ls/942 CPU: 0 PID: 942 Comm: ls Tainted: G W 6.6 #15 Call Trace: fuse_get_tree_submount+0x656/0x8b0 vfs_get_tree+0x48/0x140 fc_mount+0x13/0x50 fuse_dentry_automount+0x7a/0xb0 __traverse_mounts+0xca/0x330 step_into+0x339/0xac0 path_lookupat+0xc5/0x2f0 filename_lookup+0x163/0x2a0 vfs_statx+0xd5/0x200 do_statx+0x83/0xd0 __x64_sys_statx+0xa0/0xc0 do_syscall_64+0x37/0x90 entry_SYSCALL_64_after_hwframe+0x78/0xe2 ================================================================== Return -ENOMEM instead; the caller tears down the partially built superblock on error, matching the other error returns in this function. Fixes: 1866d779d5d2 ("fuse: Allow fuse_fill_super_common() for submounts") Signed-off-by: Baokun Li Reviewed-by: Jingbo Xu Signed-off-by: Miklos Szeredi Signed-off-by: Sasha Levin

fuse: check attributes staleness on fuse_iget()

2026-09-14T11:29:52+00:00

[ Upstream commit 69eb56f69efb866c791cc87fd7bf62adf2ffcbb3 ] Function fuse_direntplus_link() might call fuse_iget() to initialize a new fuse_inode and change its attributes. If fi->attr_version is always initialized with 0, even if the attributes returned by the FUSE_READDIR request is staled, as the new fi->attr_version is 0, fuse_change_attributes will still set the staled attributes to inode. This wrong behaviour may cause file size inconsistency even when there is no changes from server-side. To reproduce the issue, consider the following 2 programs (A and B) are running concurrently, A B ---------------------------------- -------------------------------- { /fusemnt/dir/f is a file path in a fuse mount, the size of f is 0. } readdir(/fusemnt/dir) start //Daemon set size 0 to f direntry fallocate(f, 1024) stat(f) // B see size 1024 echo 2 > /proc/sys/vm/drop_caches readdir(/fusemnt/dir) reply to kernel Kernel set 0 to the I_NEW inode stat(f) // B see size 0 In the above case, only program B is modifying the file size, however, B observes file size changing between the 2 'readonly' stat() calls. To fix this issue, we should make sure readdirplus still follows the rule of attr_version staleness checking even if the fi->attr_version is lost due to inode eviction. To identify this situation, the new fc->evict_ctr is used to record whether the eviction of inodes occurs during the readdirplus request processing. If it does, the result of readdirplus may be inaccurate; otherwise, the result of readdirplus can be trusted. Although this may still lead to incorrect invalidation, considering the relatively low frequency of evict occurrences, it should be acceptable. Link: https://lore.kernel.org/lkml/20230711043405.66256-2-zhangjiachen.jaycee@bytedance.com/ Link: https://lore.kernel.org/lkml/20241114070905.48901-1-zhangtianci.1997@bytedance.com/ Reported-by: Jiachen Zhang Suggested-by: Miklos Szeredi Signed-off-by: Zhang Tianci Signed-off-by: Miklos Szeredi Stable-dep-of: 928f659a3e36 ("fuse: check for NULL root inode in fuse_fill_super_submount") Signed-off-by: Sasha Levin

fuse: convert readdir to use folios

2026-09-14T11:29:52+00:00

[ Upstream commit 02b78c7a7a0c72aee6f600a167e6adee9417ac0e ] Convert readdir requests to use a folio instead of a page. No functional changes. Signed-off-by: Joanne Koong Reviewed-by: Josef Bacik Signed-off-by: Miklos Szeredi Stable-dep-of: 928f659a3e36 ("fuse: check for NULL root inode in fuse_fill_super_submount") Signed-off-by: Sasha Levin

fuse: support folios in struct fuse_args_pages and fuse_copy_pages()

2026-09-14T11:29:52+00:00

[ Upstream commit a669c2df36db5fa7a2674ec5ae10548760702f99 ] This adds support in struct fuse_args_pages and fuse_copy_pages() for using folios instead of pages for transferring data. Both folios and pages must be supported right now in struct fuse_args_pages and fuse_copy_pages() until all request types have been converted to use folios. Once all have been converted, then struct fuse_args_pages and fuse_copy_pages() will only support folios. Right now in fuse, all folios are one page (large folios are not yet supported). As such, copying folio->page is sufficient for copying the entire folio in fuse_copy_pages(). No functional changes. Signed-off-by: Joanne Koong Reviewed-by: Josef Bacik Signed-off-by: Miklos Szeredi Stable-dep-of: 928f659a3e36 ("fuse: check for NULL root inode in fuse_fill_super_submount") Signed-off-by: Sasha Levin

fuse: use FUSE_ROOT_ID in fuse_get_root_inode()

2026-09-14T11:29:52+00:00

[ Upstream commit 253e52437119719eb87293ef6852e13bb5ad0960 ] ...when calling fuse_iget(). Signed-off-by: Miklos Szeredi Stable-dep-of: 928f659a3e36 ("fuse: check for NULL root inode in fuse_fill_super_submount") Signed-off-by: Sasha Levin

fuse: convert to new timestamp accessors

2026-09-14T11:29:52+00:00

[ Upstream commit 3c0d5df2d03d797e66f6eef08859930a01d5d6ad ] Convert to using the new inode timestamp accessor functions. Signed-off-by: Jeff Layton Link: https://lore.kernel.org/r/20231004185347.80880-37-jlayton@kernel.org Signed-off-by: Christian Brauner Stable-dep-of: 928f659a3e36 ("fuse: check for NULL root inode in fuse_fill_super_submount") Signed-off-by: Sasha Levin

cuse: wait for pending RCU callbacks on module exit

2026-09-14T11:29:52+00:00

[ Upstream commit 4deb3edead0c0e172cc7349e8855d741d3c5e162 ] Since commit 053fc4f755ad ("fuse: fix UAF in rcu pathwalks"), fuse_conn_put() frees the fuse_conn through call_rcu() rather than synchronously. For cuse, fc->release is cuse_fc_release(), which lives in the cuse module. If the module is removed before the RCU grace period ends, the callback jumps into freed module memory: userspace / module unload | RCU softirq ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ close(/dev/cuse) | cuse_channel_release() | fuse_dev_release() | fuse_conn_put(fch->conn) | call_rcu(delayed_release) ------+---> callback queued | rmmod cuse | cuse_exit() | cuse_channel_destroy() | ... | return | | | | rcu_do_batch() | delayed_release() | fc->release() | -> cuse_fc_release() | ^^^ freed text! The freed module text is unmapped by vfree(), so the jump into the stale callback triggers a page-fault Oops. If the virtual address is subsequently reused, the callback could execute unrelated code (undefined behaviour). Fix this by calling rcu_barrier() in cuse_exit() so that any pending fuse_conn release callback completes before the module is removed. Fixes: 053fc4f755ad ("fuse: fix UAF in rcu pathwalks") Signed-off-by: Baokun Li Signed-off-by: Miklos Szeredi Signed-off-by: Sasha Levin

fuse: fix invalidate lock leak on open O_TRUNC DAX failure

2026-09-02T12:29:19+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

2026-09-02T12:29:19+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()

2026-07-24T14:02:55+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