Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: ext4: stop retrying saturated xattr cache entries ext4_xattr_block_set() retries when a cache entry selected for reuse has a saturated reference count after taking the buffer lock. The retry returns to the mbcache lookup without making that entry ineligible, so it can select the same unusable entry indefinitely. A task spinning there can hold the parent directory's i_rwsem and leave concurrent rmdir callers blocked. Normally a reusable entry has a reference count below EXT4_XATTR_REFCOUNT_MAX because the count and MBE_REUSABLE_B are updated under the same buffer lock. A corrupted filesystem can violate that invariant. The syzbot reproducer reports allocator and xattr corruption before triggering this retry loop. Check the untrusted on-disk count before incrementing it, avoiding overflow, and clear MBE_REUSABLE_B when it is already saturated. The next lookup then skips the entry that was just proven unusable. This mirrors the normal transition at EXT4_XATTR_REFCOUNT_MAX; the release path marks the entry reusable again on the exact 1024-to-1023 transition. Using the same QEMU harness and guest parameters, current unpatched Linux hung in 6 of 8 420-second trials with the do_rmdir signature; representative NMI backtraces caught the owner spinning in ext4_xattr_block_set(). The patched kernel completed 28 of 28 trials without a hung-task report; the final twelve trials exercised the reviewed overflow-safe form of the change. syzbot's patch testing also completed without reproducing the hang.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 1a56cd972ce121b6cf2517a47a578782bbd2ec95 before 119a2f053242ed75bdd2ebc95baf3ae7db6ccacf; affected 1be97463696c7291a3e1547614e96432b0bd3add before 61631352a5b405c89be579de00903b72e6888aa4; affected 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b before 8865cd664484517703df5c18a965dc3227572b87; affected 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b before a40c45268f4358207aa9c53764fed2e05f62986a; affected 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b before 889ec86464d261f026f6c334040cfc6c58c99d58; affected 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b before 4902a5cba21aeaf91e6b29e20e0967a5f6abdcd9; affected 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b before 55ee6533c1db7f7656fa8dd19637f3f8b8c08dc5; affected 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b before dbd4aea175ad3c46436acb251e817b4374628072; affected 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b before 54b6bd40898de7906acb2bccc9a96d1b8e6b4323; affected 98953044b3cdb2cb7d82e7365b659e2ed4f4ca4d; affected af8ecc8d20e72130771cc076bce7fcf17ccda6c4; affected c6fac5cf5a5098732623bcd00a8a3eb9f5465144; affected 96fa141fa295ae9428da73c56c9852053b575c04; affected 5.10.163 before 5.10.267; affected 5.15.61 before 5.15.218; affected 4.19.270 before 4.20; affected 5.4.229 before 5.5; affected 5.18.18 before 5.19; affected 5.19.2 before 5.20 |
| Linux / Linux | affected 6.0; unaffected 0 before 6.0; unaffected 5.10.267 through 5.10.*; unaffected 5.15.218 through 5.15.*; unaffected 6.1.185 through 6.1.*; unaffected 6.6.154 through 6.6.*; unaffected 6.12.106 through 6.12.*; unaffected 6.18.47 through 6.18.*; unaffected 7.1.11 through 7.1.*; unaffected 7.2.1 through 7.2.*; unaffected 7.3 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/119a2f053242ed75bdd2ebc95baf3ae7db6ccacf
- https://git.kernel.org/stable/c/61631352a5b405c89be579de00903b72e6888aa4
- https://git.kernel.org/stable/c/8865cd664484517703df5c18a965dc3227572b87
- https://git.kernel.org/stable/c/a40c45268f4358207aa9c53764fed2e05f62986a
- https://git.kernel.org/stable/c/889ec86464d261f026f6c334040cfc6c58c99d58
- https://git.kernel.org/stable/c/4902a5cba21aeaf91e6b29e20e0967a5f6abdcd9
- https://git.kernel.org/stable/c/55ee6533c1db7f7656fa8dd19637f3f8b8c08dc5
- https://git.kernel.org/stable/c/dbd4aea175ad3c46436acb251e817b4374628072
- https://git.kernel.org/stable/c/54b6bd40898de7906acb2bccc9a96d1b8e6b4323