{"id":"CVE-2025-37949","summary":"xenbus: Use kref to track req lifetime","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nxenbus: Use kref to track req lifetime\n\nMarek reported seeing a NULL pointer fault in the xenbus_thread\ncallstack:\nBUG: kernel NULL pointer dereference, address: 0000000000000000\nRIP: e030:__wake_up_common+0x4c/0x180\nCall Trace:\n \u003cTASK\u003e\n __wake_up_common_lock+0x82/0xd0\n process_msg+0x18e/0x2f0\n xenbus_thread+0x165/0x1c0\n\nprocess_msg+0x18e is req-\u003ecb(req).  req-\u003ecb is set to xs_wake_up(), a\nthin wrapper around wake_up(), or xenbus_dev_queue_reply().  It seems\nlike it was xs_wake_up() in this case.\n\nIt seems like req may have woken up the xs_wait_for_reply(), which\nkfree()ed the req.  When xenbus_thread resumes, it faults on the zero-ed\ndata.\n\nLinux Device Drivers 2nd edition states:\n\"Normally, a wake_up call can cause an immediate reschedule to happen,\nmeaning that other processes might run before wake_up returns.\"\n... which would match the behaviour observed.\n\nChange to keeping two krefs on each request.  One for the caller, and\none for xenbus_thread.  Each will kref_put() when finished, and the last\nwill free it.\n\nThis use of kref matches the description in\nDocumentation/core-api/kref.rst","modified":"2026-04-16T04:31:48.194574370Z","published":"2025-05-20T16:01:45.242Z","related":["SUSE-SU-2025:01919-1","SUSE-SU-2025:01951-1","SUSE-SU-2025:01964-1","SUSE-SU-2025:01965-1","SUSE-SU-2025:01967-1","SUSE-SU-2025:01972-1","SUSE-SU-2025:01983-1","SUSE-SU-2025:02000-1","SUSE-SU-2025:20408-1","SUSE-SU-2025:20413-1","SUSE-SU-2025:20419-1","SUSE-SU-2025:20421-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/37xxx/CVE-2025-37949.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0e94a246bb6d9538010b6c02d2b1d4717a97b2e5"},{"type":"WEB","url":"https://git.kernel.org/stable/c/1f0304dfd9d217c2f8b04a9ef4b3258a66eedd27"},{"type":"WEB","url":"https://git.kernel.org/stable/c/2466b0f66795c3c426cacc8998499f38031dbb59"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4d260a5558df4650eb87bc41b2c9ac2d6b2ba447"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8b02f85e84dc6f7c150cef40ddb69af5a25659e5"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8e9c8a0393b5f85f1820c565ab8105660f4e8f92"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cbfaf46b88a4c01b64c4186cdccd766c19ae644c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f1bcac367bc95631afbb918348f30dec887d0e1b"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2025/08/msg00010.html"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/37xxx/CVE-2025-37949.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-37949"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"fd8aa9095a95c02dcc35540a263267c29b8fda9d"},{"fixed":"0e94a246bb6d9538010b6c02d2b1d4717a97b2e5"},{"fixed":"f1bcac367bc95631afbb918348f30dec887d0e1b"},{"fixed":"4d260a5558df4650eb87bc41b2c9ac2d6b2ba447"},{"fixed":"8b02f85e84dc6f7c150cef40ddb69af5a25659e5"},{"fixed":"cbfaf46b88a4c01b64c4186cdccd766c19ae644c"},{"fixed":"8e9c8a0393b5f85f1820c565ab8105660f4e8f92"},{"fixed":"2466b0f66795c3c426cacc8998499f38031dbb59"},{"fixed":"1f0304dfd9d217c2f8b04a9ef4b3258a66eedd27"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-37949.json"}}],"schema_version":"1.7.5"}