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CVE-2026-80808

ext4: stop retrying saturated xattr cache entries

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.267, 5.15.218, 4.20, 5.5, 5.19, and 7 more
None on Exploit-DB, Metasploit or GitHub

Summary

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.

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From 1a56cd972ce121b6cf2517a47a578782bbd2ec95 · fixed in 119a2f053242ed75bdd2ebc95baf3ae7db6ccacf; From 1be97463696c7291a3e1547614e96432b0bd3add · fixed in 61631352a5b405c89be579de00903b72e6888aa4; From 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b · fixed in 8865cd664484517703df5c18a965dc3227572b87; From 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b · fixed in a40c45268f4358207aa9c53764fed2e05f62986a; From 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b · fixed in 889ec86464d261f026f6c334040cfc6c58c99d58; From 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b · fixed in 4902a5cba21aeaf91e6b29e20e0967a5f6abdcd9; From 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b · fixed in 55ee6533c1db7f7656fa8dd19637f3f8b8c08dc5; From 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b · fixed in dbd4aea175ad3c46436acb251e817b4374628072; From 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b · fixed in 54b6bd40898de7906acb2bccc9a96d1b8e6b4323; From 5.10.163 · fixed in 5.10.267; From 5.15.61 · fixed in 5.15.218; From 4.19.270 · fixed in 4.20; From 5.4.229 · fixed in 5.5; From 5.18.18 · fixed in 5.19; From 5.19.2 · fixed in 5.20

  • Linux Linux

    6.0

  • KernelLinux

    fixed in 5.10.267; From 5.11.0 · fixed in 5.15.218; From 5.16.0 · fixed in 6.1.185; From 6.0.0 · fixed in 6.6.154; From 6.2.0 · fixed in 6.12.106; From 6.7.0 · fixed in 6.18.47; From 6.13.0 · fixed in 7.1.11; From 6.19.0 · fixed in 7.2.1

References 9

git.kernel.org