{"id":"CVE-2026-92503","state":"PUBLISHED","title":"ext4: fix ABBA deadlock in ext4_xattr_inode_cache_find()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix ABBA deadlock in ext4_xattr_inode_cache_find()\n\nSyzbot/stress-ng reported an ABBA deadlock in ext4 when exercising\nconcurrent xattr workloads (using the ea_inode mount/format option).\n\nThe deadlock occurs between the running transaction and the eviction\nthread:\n- Task 1 (stress-ng): Holds a reference to a shared mbcache_entry (ce)\n  and calls ext4_xattr_inode_cache_find() -> ext4_iget() to retrieve\n  the corresponding EA inode. Since the EA inode is currently being\n  evicted, ext4_iget() blocks in __wait_on_freeing_inode() waiting for\n  eviction to complete.\n- Task 2 (eviction thread): Currently evicting the same EA inode in\n  ext4_evict_ea_inode(). It calls mb_cache_entry_wait_unused(oe) which\n  blocks waiting for Task 1 to release the reference to the mbcache_entry.\n\nTo break this deadlock, implement a new ext4_iget() configuration flag\nnamed EXT4_IGET_NOWAIT. When set, perform a non-blocking lookup of the\ninode via VFS's find_inode_nowait() API.\n\nIf the inode is currently being evicted (marked with I_FREEING or\nI_WILL_FREE) or created (I_CREATING), or if it is not present in the VFS\ninode cache (cache miss), simply skip it (returning -ENOENT) rather than\nwaiting for eviction/creation to complete, breaking the ABBA cycle.\n\nSince we return -ENOENT immediately on a cache miss, we never attempt to\nallocate a new inode or call iget_locked(), completely eliminating any\nTOCTOU race window.\n\nIf the returned inode is I_NEW, wait for its initialization to clear via\nwait_on_new_inode(). If initialization fails and the inode is unhashed\nduring wait_on_new_inode() waking up (e.g., due to an I/O read error in\nanother thread), safely drop the reference and return -ENOENT. This\nunhashed check is executed unconditionally on all cache-hit pathways to\nproperly handle concurrent initialization failures.\n\nFinally, standard validation checks (including is_bad_inode,\nEXT4_EA_INODE_FL, file_acl, and xattr flags) are executed as normal inside\ncheck_igot_inode() to fully guarantee VFS-layer safety.\n\nIn ext4_xattr_inode_cache_find(), invoke ext4_iget() with the new\nEXT4_IGET_NOWAIT flag to perform the non-blocking cache search.","publishedAt":"2026-09-17T16:10:16.062Z","updatedAt":"2026-10-30T12:35:43.123Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0752e7fb549d90c33b4d4186f11cfd25a556d1dd","status":"affected","lessThan":"e5e883ffe5230320060ea613a1acf750f3161c95","versionType":"git"},{"version":"737fb7853acd5bc8984f6f42e4bfba3334be8ae1","status":"affected","lessThan":"29a2a166450a3e89f61a486033b10cf170fde8b0","versionType":"git"},{"version":"0a46ef234756dca04623b7591e8ebb3440622f0b","status":"affected","lessThan":"d3b19b318e0e0483180d15f1d9f5e807a1fb59d5","versionType":"git"},{"version":"0a46ef234756dca04623b7591e8ebb3440622f0b","status":"affected","lessThan":"074d0620401974cbfa9b63684cdfae99c7b2059c","versionType":"git"},{"version":"0a46ef234756dca04623b7591e8ebb3440622f0b","status":"affected","lessThan":"7720fddd1fe344d14be258a2028f74ebf1569511","versionType":"git"},{"version":"0a46ef234756dca04623b7591e8ebb3440622f0b","status":"affected","lessThan":"03438084a7b8621fb5c762dd3d04cff5f2630fb2","versionType":"git"},{"version":"111103907234bffd0a34fba070ad9367de058752","status":"affected","versionType":"git"},{"version":"6.1.107","status":"affected","lessThan":"6.1.191","versionType":"semver"},{"version":"6.6.47","status":"affected","lessThan":"6.6.160","versionType":"semver"},{"version":"6.9.7","status":"affected","lessThan":"6.10","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ext4/ext4.h","fs/ext4/inode.c","fs/ext4/xattr.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.10","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.10","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ext4/ext4.h","fs/ext4/inode.c","fs/ext4/xattr.c"]}],"references":["https://git.kernel.org/stable/c/e5e883ffe5230320060ea613a1acf750f3161c95","https://git.kernel.org/stable/c/29a2a166450a3e89f61a486033b10cf170fde8b0","https://git.kernel.org/stable/c/d3b19b318e0e0483180d15f1d9f5e807a1fb59d5","https://git.kernel.org/stable/c/074d0620401974cbfa9b63684cdfae99c7b2059c","https://git.kernel.org/stable/c/7720fddd1fe344d14be258a2028f74ebf1569511","https://git.kernel.org/stable/c/03438084a7b8621fb5c762dd3d04cff5f2630fb2"],"weaknesses":[],"ingestedAt":"2026-10-30T12:54:04.478Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/92xxx/CVE-2026-92503.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-92503","state":"PUBLISHED","datePublished":"2026-09-17T16:10:16.062Z","dateUpdated":"2026-10-30T12:35:43.123Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-16T12:21:13.872Z"},"containers":{"cna":{"title":"ext4: fix ABBA deadlock in ext4_xattr_inode_cache_find()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix ABBA deadlock in ext4_xattr_inode_cache_find()\n\nSyzbot/stress-ng reported an ABBA deadlock in ext4 when exercising\nconcurrent xattr workloads (using the ea_inode mount/format option).\n\nThe deadlock occurs between the running transaction and the eviction\nthread:\n- Task 1 (stress-ng): Holds a reference to a shared mbcache_entry (ce)\n  and calls ext4_xattr_inode_cache_find() -> ext4_iget() to retrieve\n  the corresponding EA inode. Since the EA inode is currently being\n  evicted, ext4_iget() blocks in __wait_on_freeing_inode() waiting for\n  eviction to complete.\n- Task 2 (eviction thread): Currently evicting the same EA inode in\n  ext4_evict_ea_inode(). It calls mb_cache_entry_wait_unused(oe) which\n  blocks waiting for Task 1 to release the reference to the mbcache_entry.\n\nTo break this deadlock, implement a new ext4_iget() configuration flag\nnamed EXT4_IGET_NOWAIT. When set, perform a non-blocking lookup of the\ninode via VFS's find_inode_nowait() API.\n\nIf the inode is currently being evicted (marked with I_FREEING or\nI_WILL_FREE) or created (I_CREATING), or if it is not present in the VFS\ninode cache (cache miss), simply skip it (returning -ENOENT) rather than\nwaiting for eviction/creation to complete, breaking the ABBA cycle.\n\nSince we return -ENOENT immediately on a cache miss, we never attempt to\nallocate a new inode or call iget_locked(), completely eliminating any\nTOCTOU race window.\n\nIf the returned inode is I_NEW, wait for its initialization to clear via\nwait_on_new_inode(). If initialization fails and the inode is unhashed\nduring wait_on_new_inode() waking up (e.g., due to an I/O read error in\nanother thread), safely drop the reference and return -ENOENT. This\nunhashed check is executed unconditionally on all cache-hit pathways to\nproperly handle concurrent initialization failures.\n\nFinally, standard validation checks (including is_bad_inode,\nEXT4_EA_INODE_FL, file_acl, and xattr flags) are executed as normal inside\ncheck_igot_inode() to fully guarantee VFS-layer safety.\n\nIn ext4_xattr_inode_cache_find(), invoke ext4_iget() with the new\nEXT4_IGET_NOWAIT flag to perform the non-blocking cache search."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0752e7fb549d90c33b4d4186f11cfd25a556d1dd","status":"affected","lessThan":"e5e883ffe5230320060ea613a1acf750f3161c95","versionType":"git"},{"version":"737fb7853acd5bc8984f6f42e4bfba3334be8ae1","status":"affected","lessThan":"29a2a166450a3e89f61a486033b10cf170fde8b0","versionType":"git"},{"version":"0a46ef234756dca04623b7591e8ebb3440622f0b","status":"affected","lessThan":"d3b19b318e0e0483180d15f1d9f5e807a1fb59d5","versionType":"git"},{"version":"0a46ef234756dca04623b7591e8ebb3440622f0b","status":"affected","lessThan":"074d0620401974cbfa9b63684cdfae99c7b2059c","versionType":"git"},{"version":"0a46ef234756dca04623b7591e8ebb3440622f0b","status":"affected","lessThan":"7720fddd1fe344d14be258a2028f74ebf1569511","versionType":"git"},{"version":"0a46ef234756dca04623b7591e8ebb3440622f0b","status":"affected","lessThan":"03438084a7b8621fb5c762dd3d04cff5f2630fb2","versionType":"git"},{"version":"111103907234bffd0a34fba070ad9367de058752","status":"affected","versionType":"git"},{"version":"6.1.107","status":"affected","lessThan":"6.1.191","versionType":"semver"},{"version":"6.6.47","status":"affected","lessThan":"6.6.160","versionType":"semver"},{"version":"6.9.7","status":"affected","lessThan":"6.10","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ext4/ext4.h","fs/ext4/inode.c","fs/ext4/xattr.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.10","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.10","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ext4/ext4.h","fs/ext4/inode.c","fs/ext4/xattr.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/e5e883ffe5230320060ea613a1acf750f3161c95"},{"url":"https://git.kernel.org/stable/c/29a2a166450a3e89f61a486033b10cf170fde8b0"},{"url":"https://git.kernel.org/stable/c/d3b19b318e0e0483180d15f1d9f5e807a1fb59d5"},{"url":"https://git.kernel.org/stable/c/074d0620401974cbfa9b63684cdfae99c7b2059c"},{"url":"https://git.kernel.org/stable/c/7720fddd1fe344d14be258a2028f74ebf1569511"},{"url":"https://git.kernel.org/stable/c/03438084a7b8621fb5c762dd3d04cff5f2630fb2"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:35:43.123Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1.107","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6.47","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.12.114"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.18.57"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"7.2.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"7.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.9.7"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}