Use After Free Affecting kernel-default-livepatch package, versions <6.4.0-150600.23.38.1


Severity

Recommended
0.0
high
0
10

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.03% (7th percentile)

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  • Snyk IDSNYK-SLES156-KERNELDEFAULTLIVEPATCH-8726405
  • published14 Feb 2025
  • disclosed13 Feb 2025

Introduced: 13 Feb 2025

CVE-2024-56759  (opens in a new tab)
CWE-416  (opens in a new tab)

How to fix?

Upgrade SLES:15.6 kernel-default-livepatch to version 6.4.0-150600.23.38.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-default-livepatch package and not the kernel-default-livepatch package as distributed by SLES. See How to fix? for SLES:15.6 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix use-after-free when COWing tree bock and tracing is enabled

When a COWing a tree block, at btrfs_cow_block(), and we have the tracepoint trace_btrfs_cow_block() enabled and preemption is also enabled (CONFIG_PREEMPT=y), we can trigger a use-after-free in the COWed extent buffer while inside the tracepoint code. This is because in some paths that call btrfs_cow_block(), such as btrfs_search_slot(), we are holding the last reference on the extent buffer @buf so btrfs_force_cow_block() drops the last reference on the @buf extent buffer when it calls free_extent_buffer_stale(buf), which schedules the release of the extent buffer with RCU. This means that if we are on a kernel with preemption, the current task may be preempted before calling trace_btrfs_cow_block() and the extent buffer already released by the time trace_btrfs_cow_block() is called, resulting in a use-after-free.

Fix this by moving the trace_btrfs_cow_block() from btrfs_cow_block() to btrfs_force_cow_block() before the COWed extent buffer is freed. This also has a side effect of invoking the tracepoint in the tree defrag code, at defrag.c:btrfs_realloc_node(), since btrfs_force_cow_block() is called there, but this is fine and it was actually missing there.

CVSS Base Scores

version 3.1