{"id":"DEBIAN-CVE-2022-49272","details":"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-\u003ebuffer_mutex and the mm-\u003emmap_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-\u003emmap_mutex is already held.  Meanwhile, the copy_from/to_user calls at read/write operations also take the mm-\u003emmap_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-\u003ebuffer_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.","modified":"2026-09-01T16:05:30.375631202Z","published":"2025-02-26T07:01:04.097Z","upstream":["CVE-2022-49272"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2022-49272"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.17.3-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2022-49272.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.17.3-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2022-49272.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.17.3-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2022-49272.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}