CVE-2025-37949

In the Linux kernel, the following vulnerability has been resolved: xenbus: Use kref to track req lifetime Marek reported seeing a NULL pointer fault in the xenbus_thread callstack: BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: e030:__wake_up_common+0x4c/0x180 Call Trace: <TASK> __wake_up_common_lock+0x82/0xd0 process_msg+0x18e/0x2f0 xenbus_thread+0x165/0x1c0 process_msg+0x18e is req->cb(req). req->cb is set to xs_wake_up(), a thin wrapper around wake_up(), or xenbus_dev_queue_reply(). It seems like it was xs_wake_up() in this case. It seems like req may have woken up the xs_wait_for_reply(), which kfree()ed the req. When xenbus_thread resumes, it faults on the zero-ed data. Linux Device Drivers 2nd edition states: "Normally, a wake_up call can cause an immediate reschedule to happen, meaning that other processes might run before wake_up returns." ... which would match the behaviour observed. Change to keeping two krefs on each request. One for the caller, and one for xenbus_thread. Each will kref_put() when finished, and the last will free it. This use of kref matches the description in Documentation/core-api/kref.rst

• linux linux kernel (>= 4.11 < 5.4.294) • linux linux kernel (>= 5.5 < 5.10.238) • linux linux kernel (>= 5.11 < 5.15.183) • linux linux kernel (>= 5.16 < 6.1.139) • linux linux kernel (>= 6.2 < 6.6.91) • linux linux kernel (>= 6.7 < 6.12.29) • linux linux kernel (>= 6.13 < 6.14.7) • linux linux kernel 6.15 • debian debian linux 11.0