CVE-2025-37949
xenbus: Use kref to track req lifetime
We use these services and cookies to improve your user experience. You may opt out if you wish, however, this may limit some features on this site.
Please see our statement on Data Privacy.
xenbus: Use kref to track req lifetime
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
Reserved 2025-04-16 | Published 2025-05-20 | Updated 2025-05-26 | Assigner Linuxgit.kernel.org/...c/4d260a5558df4650eb87bc41b2c9ac2d6b2ba447
git.kernel.org/...c/8b02f85e84dc6f7c150cef40ddb69af5a25659e5
git.kernel.org/...c/cbfaf46b88a4c01b64c4186cdccd766c19ae644c
git.kernel.org/...c/8e9c8a0393b5f85f1820c565ab8105660f4e8f92
git.kernel.org/...c/2466b0f66795c3c426cacc8998499f38031dbb59
git.kernel.org/...c/1f0304dfd9d217c2f8b04a9ef4b3258a66eedd27
Support options
