Linux Kernel up to 6.1.159/6.6.119/6.12.63/6.18.2 fuse mm/filemap.c fuse_prepare_release deadlock

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.1.159/6.6.119/6.12.63/6.18.2. It has been classified as critical. Impacted is the function fuse_prepare_release of the file mm/filemap.c of the component fuse. Performing a manipulation results in deadlock. This vulnerability was named CVE-2025-68821. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as critical, was found in Linux Kernel up to 6.1.159/6.6.119/6.12.63/6.18.2. This affects the function fuse_prepare_release of the file mm/filemap.c of the component fuse. The manipulation with an unknown input leads to a deadlock vulnerability. CWE is classifying the issue as CWE-833. The product contains multiple threads or executable segments that are waiting for each other to release a necessary lock, resulting in deadlock. This is going to have an impact on availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: fuse: fix readahead reclaim deadlock Commit e26ee4efbc79 ("fuse: allocate ff->release_args only if release is needed") skips allocating ff->release_args if the server does not implement open. However in doing so, fuse_prepare_release() now skips grabbing the reference on the inode, which makes it possible for an inode to be evicted from the dcache while there are inflight readahead requests. This causes a deadlock if the server triggers reclaim while servicing the readahead request and reclaim attempts to evict the inode of the file being read ahead. Since the folio is locked during readahead, when reclaim evicts the fuse inode and fuse_evict_inode() attempts to remove all folios associated with the inode from the page cache (truncate_inode_pages_range()), reclaim will block forever waiting for the lock since readahead cannot relinquish the lock because it is itself blocked in reclaim: >>> stack_trace(1504735) folio_wait_bit_common (mm/filemap.c:1308:4) folio_lock (./include/linux/pagemap.h:1052:3) truncate_inode_pages_range (mm/truncate.c:336:10) fuse_evict_inode (fs/fuse/inode.c:161:2) evict (fs/inode.c:704:3) dentry_unlink_inode (fs/dcache.c:412:3) __dentry_kill (fs/dcache.c:615:3) shrink_kill (fs/dcache.c:1060:12) shrink_dentry_list (fs/dcache.c:1087:3) prune_dcache_sb (fs/dcache.c:1168:2) super_cache_scan (fs/super.c:221:10) do_shrink_slab (mm/shrinker.c:435:9) shrink_slab (mm/shrinker.c:626:10) shrink_node (mm/vmscan.c:5951:2) shrink_zones (mm/vmscan.c:6195:3) do_try_to_free_pages (mm/vmscan.c:6257:3) do_swap_page (mm/memory.c:4136:11) handle_pte_fault (mm/memory.c:5562:10) handle_mm_fault (mm/memory.c:5870:9) do_user_addr_fault (arch/x86/mm/fault.c:1338:10) handle_page_fault (arch/x86/mm/fault.c:1481:3) exc_page_fault (arch/x86/mm/fault.c:1539:2) asm_exc_page_fault+0x22/0x27 Fix this deadlock by allocating ff->release_args and grabbing the reference on the inode when preparing the file for release even if the server does not implement open. The inode reference will be dropped when the last reference on the fuse file is dropped (see fuse_file_put() -> fuse_release_end()).

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2025-68821 since 12/24/2025. The exploitability is told to be difficult. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 298659 (Debian dla-4476 : linux-config-6.1 - security update), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.1.160, 6.6.120, 6.12.64, 6.18.3 or 6.19-rc1 eliminates this vulnerability. Applying the patch 4703bc0e8cd3409acb1476a70cb5b7ff943cf39a/cf74785c00b8b1c0c4a9dd74bfa9c22d62e2d99f/fbba8b00bbe4e4f958a2b0654cc1219a7e6597f6/e0d6de83a4cc22bbac72713f3a58121af36cc411/bd5603eaae0aabf527bfb3ce1bb07e979ce5bd50 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (298659). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.1.159
• 6.6.119
• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
• 6.12.5
• 6.12.6
• 6.12.7
• 6.12.8
• 6.12.9
• 6.12.10
• 6.12.11
• 6.12.12
• 6.12.13
• 6.12.14
• 6.12.15
• 6.12.16
• 6.12.17
• 6.12.18
• 6.12.19
• 6.12.20
• 6.12.21
• 6.12.22
• 6.12.23
• 6.12.24
• 6.12.25
• 6.12.26
• 6.12.27
• 6.12.28
• 6.12.29
• 6.12.30
• 6.12.31
• 6.12.32
• 6.12.33
• 6.12.34
• 6.12.35
• 6.12.36
• 6.12.37
• 6.12.38
• 6.12.39
• 6.12.40
• 6.12.41
• 6.12.42
• 6.12.43
• 6.12.44
• 6.12.45
• 6.12.46
• 6.12.47
• 6.12.48
• 6.12.49
• 6.12.50
• 6.12.51
• 6.12.52
• 6.12.53
• 6.12.54
• 6.12.55
• 6.12.56
• 6.12.57
• 6.12.58
• 6.12.59
• 6.12.60
• 6.12.61
• 6.12.62
• 6.12.63
• 6.18.0
• 6.18.1
• 6.18.2

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Entryinfo

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