CVE-2026-45920ext4: fix dirtyclusters double decrement on fs shutdown

Description

In the Linux kernel, the following vulnerability has been resolved: ext4: fix dirtyclusters double decrement on fs shutdown fstests test generic/388 occasionally reproduces a warning in ext4_put_super() associated with the dirty clusters count: WARNING: CPU: 7 PID: 76064 at fs/ext4/super.c:1324 ext4_put_super+0x48c/0x590 [ext4] Tracing the failure shows that the warning fires due to an s_dirtyclusters_counter value of -1. IOW, this appears to be a spurious decrement as opposed to some sort of leak. Further tracing of the dirty cluster count deltas and an LLM scan of the resulting output identified the cause as a double decrement in the error path between ext4_mb_mark_diskspace_used() and the caller ext4_mb_new_blocks(). First, note that generic/388 is a shutdown vs. fsstress test and so produces a random set of operations and shutdown injections. In the problematic case, the shutdown triggers an error return from the ext4_handle_dirty_metadata() call(s) made from ext4_mb_mark_context(). The changed value is non-zero at this point, so ext4_mb_mark_diskspace_used() does not exit after the error bubbles up from ext4_mb_mark_context(). Instead, the former decrements both cluster counters and returns the error up to ext4_mb_new_blocks(). The latter falls into the !ar->len out path which decrements the dirty clusters counter a second time, creating the inconsistency. To avoid this problem and simplify ownership of the cluster reservation in this codepath, lift the counter reduction to a single place in the caller. This makes it more clear that ext4_mb_new_blocks() is responsible for acquiring cluster reservation (via ext4_claim_free_clusters()) in the !delalloc case as well as releasing it, regardless of whether it ends up consumed or returned due to failure.

Timeline

Scores

EPSS (exploitation in 30 days)

0.15% · top 96% of all CVEs (13 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.

Affected products

• Linux · Linux

  • affected 0087d9fb3f29f59e8d42c8b058376d80e5adde4c – < 523d5a4df3c649fa305c89efb552ec62a1ce9d3d
  • affected 0087d9fb3f29f59e8d42c8b058376d80e5adde4c – < ca408af08544d96769c93a3d81a7f63f61129e95
  • affected 0087d9fb3f29f59e8d42c8b058376d80e5adde4c – < 55576fa14771d33994c29a9ae960e07bb3f56c20
  • affected 0087d9fb3f29f59e8d42c8b058376d80e5adde4c – < dbc4e10619ed87a50e637b96f2e574df36a7a769
  • affected 0087d9fb3f29f59e8d42c8b058376d80e5adde4c – < 61e372122b6d95aec940fdaea0a16f988f359897
  • affected 0087d9fb3f29f59e8d42c8b058376d80e5adde4c – < 3924aea2c33df3864929c1acd178bfc29d8f005f
  • affected 0087d9fb3f29f59e8d42c8b058376d80e5adde4c – < 81982a11406c5da6c6e2b188028e7056e16b7128
  • affected 0087d9fb3f29f59e8d42c8b058376d80e5adde4c – < 94a8cea54cd935c54fa2fba70354757c0fc245e3

• Linux · Linux

  • affected 2.6.29
  • unaffected < 2.6.29
  • unaffected 5.10.253 – ≤ 5.10.*
  • unaffected 5.15.203 – ≤ 5.15.*
  • unaffected 6.1.167 – ≤ 6.1.*
  • unaffected 6.6.130 – ≤ 6.6.*
  • unaffected 6.12.75 – ≤ 6.12.*
  • unaffected 6.18.14 – ≤ 6.18.*
  • unaffected 6.19.4 – ≤ 6.19.*
  • unaffected 7.0 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-32386 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-45920](https://cveledger.app/badge/CVE-2026-45920.svg)](https://cveledger.app/cve/CVE-2026-45920)

Record last updated 6 Nov 2026, 15:53 UTC.