Double Free Affecting kernel-default-vdso package, versions <6.12.0-160000.6.1


Severity

Recommended
0.0
medium
0
10

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.03% (10th percentile)

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  • Snyk IDSNYK-SLES1600-KERNELDEFAULTVDSO-13932947
  • published13 Nov 2025
  • disclosed6 Nov 2025

Introduced: 6 Nov 2025

NewCVE-2025-38338  (opens in a new tab)
CWE-415  (opens in a new tab)

How to fix?

Upgrade SLES:16.0.0 kernel-default-vdso to version 6.12.0-160000.6.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-default-vdso package and not the kernel-default-vdso package as distributed by SLES. See How to fix? for SLES:16.0.0 relevant fixed versions and status.

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

fs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()

Sometimes, when a file was read while it was being truncated by another NFS client, the kernel could deadlock because folio_unlock() was called twice, and the second call would XOR back the PG_locked flag.

Most of the time (depending on the timing of the truncation), nobody notices the problem because folio_unlock() gets called three times, which flips PG_locked back off:

  1. vfs_read, nfs_read_folio, ... nfs_read_add_folio, nfs_return_empty_folio
  2. vfs_read, nfs_read_folio, ... netfs_read_collection, netfs_unlock_abandoned_read_pages
  3. vfs_read, ... nfs_do_read_folio, nfs_read_add_folio, nfs_return_empty_folio

The problem is that nfs_read_add_folio() is not supposed to unlock the folio if fscache is enabled, and a nfs_netfs_folio_unlock() check is missing in nfs_return_empty_folio().

Rarely this leads to a warning in netfs_read_collection():

------------[ cut here ]------------ R=0000031c: folio 10 is not locked WARNING: CPU: 0 PID: 29 at fs/netfs/read_collect.c:133 netfs_read_collection+0x7c0/0xf00 [...] Workqueue: events_unbound netfs_read_collection_worker RIP: 0010:netfs_read_collection+0x7c0/0xf00 [...] Call Trace: <TASK> netfs_read_collection_worker+0x67/0x80 process_one_work+0x12e/0x2c0 worker_thread+0x295/0x3a0

Most of the time, however, processes just get stuck forever in folio_wait_bit_common(), waiting for PG_locked to disappear, which never happens because nobody is really holding the folio lock.

CVSS Base Scores

version 3.1