Double Free Affecting kernel-macros package, versions <6.4.0-150700.53.73.1


Severity

Recommended
0.0
medium
0
10

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.15% (5th percentile)

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  • Snyk IDSNYK-SLES157-KERNELMACROS-18206532
  • published22 Jul 2026
  • disclosed21 Jul 2026

Introduced: 21 Jul 2026

NewCVE-2026-45920  (opens in a new tab)
CWE-415  (opens in a new tab)

How to fix?

Upgrade SLES:15.7 kernel-macros to version 6.4.0-150700.53.73.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-macros package and not the kernel-macros package as distributed by SLES. See How to fix? for SLES:15.7 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1