ext4: fix ABBA deadlock in ext4_xattr_inode_cache_find()
Severity and exploitation
KEV coverage does not rule out exploitation.
Severity
unknownCVSS measures technical severity, not the likelihood of an attack.
Known exploitation
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Public exploit
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Remediation
Fix status not established
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What this means
In the Linux kernel, the following vulnerability has been resolved:
Source excerpt · LinuxAttack conditions
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Review supporting sources →Affected versions
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Linux · Linux
Linux
10 ranges
Linux · Linux
Linux
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affected
0752e7fb549d90c33b4d4186f11cfd25a556d1dd → before e5e883ffe5230320060ea613a1acf750f3161c95
git versions
737fb7853acd5bc8984f6f42e4bfba3334be8ae1 → before 29a2a166450a3e89f61a486033b10cf170fde8b0
git versions
0a46ef234756dca04623b7591e8ebb3440622f0b → before d3b19b318e0e0483180d15f1d9f5e807a1fb59d5
git versions
0a46ef234756dca04623b7591e8ebb3440622f0b → before 074d0620401974cbfa9b63684cdfae99c7b2059c
git versions
0a46ef234756dca04623b7591e8ebb3440622f0b → before 7720fddd1fe344d14be258a2028f74ebf1569511
git versions
0a46ef234756dca04623b7591e8ebb3440622f0b → before 03438084a7b8621fb5c762dd3d04cff5f2630fb2
git versions
111103907234bffd0a34fba070ad9367de058752
git versions
6.1.107 → before 6.1.191
semver versions
6.6.47 → before 6.6.160
semver versions
6.9.7 → before 6.10
semver versions
Other versions: unaffected
Linux · Linux
Linux
8 ranges
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Linux
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affected
6.10
unaffected
0 → before 6.10
semver versions
6.1.191 → through 6.1.*
semver versions
6.6.160 → through 6.6.*
semver versions
6.12.114 → through 6.12.*
semver versions
6.18.57 → through 6.18.*
semver versions
7.2.6 → through 7.2.*
semver versions
7.3 → through *
original_commit_for_fix versions
Other versions: affected
What to do
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Public exploit evidence
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Original source description
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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).
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.
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.
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.
References
6 sourcesInside the record
Evidence available
Describes the evidence in this view, not whether the product is safe.
Original records
CVE-2026-92503View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.
cve.new JSON →Environment requirements
These conditions apply together as specified by the publisher. A matching product name alone does not establish exposure.
Linux · platform conditions
Any condition may hold
Vulnerable product
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*From (inclusive): 6.1.107
Before: 6.1.191
Vulnerable product
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*From (inclusive): 6.6.47
Before: 6.6.160
Vulnerable product
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*From (inclusive): 6.10
Before: 6.12.114
Vulnerable product
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*From (inclusive): 6.10
Before: 6.18.57
Vulnerable product
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*From (inclusive): 6.10
Before: 7.2.6
Vulnerable product
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*From (inclusive): 6.10
Before: 7.3
Vulnerable product
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*From (inclusive): 6.9.7
Applicability preview
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