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Fencer Vulns
medium 5.5

CVE-2022-49272 json

ALSA: pcm: Fix potential AB/BA lock with buffer_mutex and mmap_lock

published 2025-02-26 20 mo ago modified 2026-06-17 4 mo ago also EUVD-2022-54954

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 10%
public exploits
0
none known

Summary

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

ALSA: pcm: Fix potential AB/BA lock with buffer_mutex and mmap_lock

syzbot caught a potential deadlock between the PCM runtime->buffer_mutex and the mm->mmap_lock. It was brought by the recent fix to cover the racy read/write and other ioctls, and in that commit, I overlooked a (hopefully only) corner case that may take the revert lock, namely, the OSS mmap. The OSS mmap operation exceptionally allows to re-configure the parameters inside the OSS mmap syscall, where mm->mmap_mutex is already held. Meanwhile, the copy_from/to_user calls at read/write operations also take the mm->mmap_lock internally, hence it may lead to a AB/BA deadlock.

A similar problem was already seen in the past and we fixed it with a refcount (in commit b248371628aa). The former fix covered only the call paths with OSS read/write and OSS ioctls, while we need to cover the concurrent access via both ALSA and OSS APIs now.

This patch addresses the problem above by replacing the buffer_mutex lock in the read/write operations with a refcount similar as we've used for OSS. The new field, runtime->buffer_accessing, keeps the number of concurrent read/write operations. Unlike the former buffer_mutex protection, this protects only around the copy_from/to_user() calls; the other codes are basically protected by the PCM stream lock. The refcount can be a negative, meaning blocked by the ioctls. If a negative value is seen, the read/write aborts with -EBUSY. In the ioctl side, OTOH, they check this refcount, too, and set to a negative value for blocking unless it's already being accessed.

Patch / fix

  • Linux Linux 5.10.110, 5.15.33, 5.16.19, 5.17.2
  • linux Debian 14, Debian 13, Debian 12 5.17.3-1

debian advisories DEBIAN-CVE-2022-49272

  • kernel RHEL 9 5.14.0-162.6.1.el9_1
  • perf RHEL 9 5.14.0-162.6.1.el9_1
  • bpftool RHEL 9 5.14.0-162.6.1.el9_1
  • kernel-core RHEL 9 5.14.0-162.6.1.el9_1
  • kernel-tools RHEL 9 5.14.0-162.6.1.el9_1
  • python3-perf RHEL 9 5.14.0-162.6.1.el9_1
  • kernel-modules RHEL 9 5.14.0-162.6.1.el9_1
  • kernel-zfcpdump RHEL 9 5.14.0-162.6.1.el9_1

red hat advisories RHSA-2022:8267RHSA-2022:7683

  • kernel-64kb SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS, Enterprise Storage 7.1 5.3.18-150300.59.201.1
  • kernel-syms SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.201.1
  • kernel-source SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.201.1
  • kernel-default SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE Micro 5.2 +5 more 5.3.18-150300.59.201.1
  • kernel-preempt SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.201.1
  • kernel-obs-build SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.201.1
  • kernel-default-base SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE Micro 5.2 +3 more 5.3.18-150300.59.201.1.150300.18.120.1
  • kernel-64kb SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS, SLE High Performance Computing 15 SP5-ESPOS 5.14.21-150500.55.100.1

suse advisories SUSE-SU-2026:0385-1SUSE-SU-2025:1293-1SUSE-SU-2025:1263-1SUSE-SU-2025:1241-1SUSE-SU-2025:1194-1SUSE-SU-2025:1183-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2022-49272 updated cvss 5.5

kernel: ALSA: pcm: Fix potential AB/BA lock with buffer_mutex and mmap_lock

  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +6 more
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    affected: no fix available
  • Red Hat CodeReady Linux Builder (v. 8) kernel-debuginfo-common-x86_64 4.18.0-425.3.1.el8, kernel-debuginfo-common-aarch64 4.18.0-425.3.1.el8, kernel-debuginfo-common-ppc64le 4.18.0-425.3.1.el8
    fixed: vendor fix RHSA-2022:7683
  • Red Hat CodeReady Linux Builder (v. 9) kernel-debuginfo-common-s390x 5.14.0-162.6.1.el9_1, kernel-debuginfo-common-x86_64 5.14.0-162.6.1.el9_1, kernel-debuginfo-common-aarch64 5.14.0-162.6.1.el9_1, kernel-debuginfo-common-ppc64le 5.14.0-162.6.1.el9_1 Red Hat Enterprise Linux AppStream (v. 9) perf 5.14.0-162.6.1.el9_1, kernel-devel-matched 5.14.0-162.6.1.el9_1, kernel-debug-devel-matched 5.14.0-162.6.1.el9_1, kernel-debuginfo-common-s390x 5.14.0-162.6.1.el9_1, kernel-zfcpdump-devel-matched 5.14.0-162.6.1.el9_1, kernel-debuginfo-common-x86_64 5.14.0-162.6.1.el9_1, +2 more
    fixed: vendor fix RHSA-2022:8267
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-425.3.1.el8, kernel 4.18.0-425.3.1.el8, bpftool 4.18.0-425.3.1.el8, kernel-core 4.18.0-425.3.1.el8, kernel-tools 4.18.0-425.3.1.el8, python3-perf 4.18.0-425.3.1.el8, +15 more
    fixed: vendor fix RHSA-2022:7683
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-162.6.1.el9_1, bpftool 5.14.0-162.6.1.el9_1, kernel-core 5.14.0-162.6.1.el9_1, kernel-tools 5.14.0-162.6.1.el9_1, python3-perf 5.14.0-162.6.1.el9_1, kernel-modules 5.14.0-162.6.1.el9_1, +14 more
    fixed: vendor fix RHSA-2022:8267
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 10 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.20% chance of exploitation in the next 30 days, higher than 10% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Weakness
Technology feeds

References

Sources

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