CVE-2026-92503
In the Linux kernel, the following vulnerability has been resolved:
ext4: fix ABBA deadlock in ext4_xattr_inode_cache_find()
Syzbot/stress-ng reported an ABBA deadlock in ext4 when exercising concurrent xattr workloads (using the ea_inode mount/format option).
To break this deadlock, implement a new ext4_iget() configuration flag named EXT4_IGET_NOWAIT. When set, perform a non-blocking lookup of the inode via VFS's find_inode_nowait() API.
If the inode is currently being evicted (marked with I_FREEING or I_WILL_FREE) or created (I_CREATING), or if it is not present in the VFS inode cache (cache miss), simply skip it (returning -ENOENT) rather than waiting for eviction/creation to complete, breaking the ABBA cycle.
Leer descripción completaMostrar menos
Since we return -ENOENT immediately on a cache miss, we never attempt to allocate a new inode or call iget_locked(), completely eliminating any TOCTOU race window.
If the returned inode is I_NEW, wait for its initialization to clear via wait_on_new_inode(). If initialization fails and the inode is unhashed during wait_on_new_inode() waking up (e.g., due to an I/O read error in another thread), safely drop the reference and return -ENOENT. This unhashed check is executed unconditionally on all cache-hit pathways to properly handle concurrent initialization failures.
Finally, standard validation checks (including is_bad_inode, EXT4_EA_INODE_FL, file_acl, and xattr flags) are executed as normal inside check_igot_inode() to fully guarantee VFS-layer safety.
In ext4_xattr_inode_cache_find(), invoke ext4_iget() with the new EXT4_IGET_NOWAIT flag to perform the non-blocking cache search.
Detalles técnicos trazas, registros y código del informe original
The deadlock occurs between the running transaction and the eviction thread: - Task 1 (stress-ng): Holds a reference to a shared mbcache_entry (ce) and calls ext4_xattr_inode_cache_find() -> ext4_iget() to retrieve the corresponding EA inode. Since the EA inode is currently being evicted, ext4_iget() blocks in __wait_on_freeing_inode() waiting for eviction to complete. - Task 2 (eviction thread): Currently evicting the same EA inode in ext4_evict_ea_inode(). It calls mb_cache_entry_wait_unused(oe) which blocks waiting for Task 1 to release the reference to the mbcache_entry.
CVSS
NVD no ha asignado puntuación CVSS a esta CVE (habitual desde el cambio de política de abril de 2026).
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.20%
- Percentil entre todas las CVEs puntuadas: 9
- Fecha de la puntuación: 5/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
JSON original (NVD)
Mostrar
{
"id": "CVE-2026-92503",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "0a46ef234756dca04623b7591e8ebb3440622f0b",
"lessThan": "7720fddd1fe344d14be258a2028f74ebf1569511",
"versionType": "git"
},
{
"status": "affected",
"version": "0a46ef234756dca04623b7591e8ebb3440622f0b",
"lessThan": "03438084a7b8621fb5c762dd3d04cff5f2630fb2",
"versionType": "git"
},
{
"status": "affected",
"version": "0752e7fb549d90c33b4d4186f11cfd25a556d1dd",
"versionType": "git"
},
{
"status": "affected",
"version": "737fb7853acd5bc8984f6f42e4bfba3334be8ae1",
"versionType": "git"
},
{
"status": "affected",
"version": "111103907234bffd0a34fba070ad9367de058752",
"versionType": "git"
},
{
"status": "affected",
"version": "6.1.107",
"lessThan": "6.2",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.6.47",
"lessThan": "6.7",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.9.7",
"lessThan": "6.10",
"versionType": "semver"
}
],
"programFiles": [
"fs/ext4/ext4.h",
"fs/ext4/inode.c",
"fs/ext4/xattr.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.10"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.10",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "7.2.6",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3-rc1",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/ext4/ext4.h",
"fs/ext4/inode.c",
"fs/ext4/xattr.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-09-17T17:17:52.820",
"references": [
{
"url": "https://git.kernel.org/stable/c/03438084a7b8621fb5c762dd3d04cff5f2630fb2",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/7720fddd1fe344d14be258a2028f74ebf1569511",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"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."
}
],
"lastModified": "2026-09-17T17:17:52.820",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}