CVE-2022-49272

/// Technical description

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 addres

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References