CVE-2026-92503

CVE CVE-2026-92503EUVD EUVD-2026-82124Published 2026-09-17T16:10:16.000Z

What the advisory describes

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.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

• Linux — Linux 6.1.107 <6.2; 6.6.47 <6.7; patch: 0; 0a46ef234756dca04623b7591e8ebb3440622f0b <03438084a7b8621fb5c762dd3d04cff5f2630fb2; 6.10; 737fb7853acd5bc8984f6f42e4bfba3334be8ae1; 0752e7fb549d90c33b4d4186f11cfd25a556d1dd; patch: 7.3-rc1; patch: 7.2.6; 0a46ef234756dca04623b7591e8ebb3440622f0b <7720fddd1fe344d14be258a2028f74ebf1569511; 6.9.7 <6.10; 111103907234bffd0a34fba070ad9367de058752

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

• Linux — Linux

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