CVE-2025-68821

Description

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()).

Gravité et risque d'exploitation

CVE-2025-68821 obtient un score CVSS de 0.0/10, soit une gravité non évaluée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.21 %, ce qui la place devant 10.2 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions 6.12.64, 6.9, <=6.1.*, e26ee4efbc79610b20e7abe9d96c87f33dacc1ff, <=6.12.*, 6.1.160, 0, 6.6.120, <5.15.198, c7ec75f3cbf73bd46f479f7d6942585f765715da, <4703bc0e8cd3409acb1476a70cb5b7ff943cf39a, 5.15.198, <=6.6.*, <6.1.160, <bd5603eaae0aabf527bfb3ce1bb07e979ce5bd50, 6.18.3, <e0d6de83a4cc22bbac72713f3a58121af36cc411, a39f70d63f4373a598820d9491719e44cd60afe9, <=6.18.*, <6.6.120, 6.1.158, 6.6.115, <cbbf3f1bb9f834bb2acbb61ddca74363456e19cd, <fbba8b00bbe4e4f958a2b0654cc1219a7e6597f6, 7d38aa079ed859b73f4460aab89c7619b04963b8, <=*, <=5.15.*, 6.19, <6.9, <cf74785c00b8b1c0c4a9dd74bfa9c22d62e2d99f, 5.15.196) est présent sur votre parc.
• Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
• À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
• Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

• https://git.kernel.org/stable/c/cbbf3f1bb9f834bb2acbb61ddca74363456e19cd
• https://git.kernel.org/stable/c/4703bc0e8cd3409acb1476a70cb5b7ff943cf39a
• https://git.kernel.org/stable/c/cf74785c00b8b1c0c4a9dd74bfa9c22d62e2d99f
• https://git.kernel.org/stable/c/fbba8b00bbe4e4f958a2b0654cc1219a7e6597f6
• https://git.kernel.org/stable/c/e0d6de83a4cc22bbac72713f3a58121af36cc411
• https://git.kernel.org/stable/c/bd5603eaae0aabf527bfb3ce1bb07e979ce5bd50