{"cve":"CVE-2022-49272","nvd":{"published":"2025-02-26T07:01:04.097","modified":"2026-06-17T05:17:33.750","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: pcm: Fix potential AB/BA lock with buffer_mutex and mmap_lock\n\nsyzbot caught a potential deadlock between the PCM\nruntime->buffer_mutex and the mm->mmap_lock.  It was brought by the\nrecent fix to cover the racy read/write and other ioctls, and in that\ncommit, I overlooked a (hopefully only) corner case that may take the\nrevert lock, namely, the OSS mmap.  The OSS mmap operation\nexceptionally allows to re-configure the parameters inside the OSS\nmmap syscall, where mm->mmap_mutex is already held.  Meanwhile, the\ncopy_from/to_user calls at read/write operations also take the\nmm->mmap_lock internally, hence it may lead to a AB/BA deadlock.\n\nA similar problem was already seen in the past and we fixed it with a\nrefcount (in commit b248371628aa).  The former fix covered only the\ncall paths with OSS read/write and OSS ioctls, while we need to cover\nthe concurrent access via both ALSA and OSS APIs now.\n\nThis patch addresses the problem above by replacing the buffer_mutex\nlock in the read/write operations with a refcount similar as we've\nused for OSS.  The new field, runtime->buffer_accessing, keeps the\nnumber of concurrent read/write operations.  Unlike the former\nbuffer_mutex protection, this protects only around the\ncopy_from/to_user() calls; the other codes are basically protected by\nthe PCM stream lock.  The refcount can be a negative, meaning blocked\nby the ioctls.  If a negative value is seen, the read/write aborts\nwith -EBUSY.  In the ioctl side, OTOH, they check this refcount, too,\nand set to a negative value for blocking unless it's already being\naccessed.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":["CWE-667"],"references":["https://git.kernel.org/stable/c/40f4cffbe13a51faf136faf5f9ef6847782cd595","https://git.kernel.org/stable/c/7777744e92a0b30e3e0cce2758d911837011ebd9","https://git.kernel.org/stable/c/7e9133607e1501c94881be35e118d8f84d96dcb4","https://git.kernel.org/stable/c/9017201e8d8c6d1472273361389ed431188584a0","https://git.kernel.org/stable/c/9661bf674d6a82b76e4ae424438a8ce1e3ed855d"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:59:48.811064707+00:00"},"epss":{"cve":"CVE-2022-49272","score":0.00204,"percentile":0.10425,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}