CVE-2025-37949

xenbus: Use kref to track req lifetime

State: Published
Severity: 7.8 High
Published: May 20, 2025
Updated: Oct 15, 2026
Reserved: Apr 16, 2025

Description

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

Scores

CVSS	Score	Vector	Source
3.1	7.8 High	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H	Linux

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	fd8aa9095a95c02dcc35540a263267c29b8fda9d to before 0e94a246bb6d9538010b6c02d2b1d4717a97b2e5Affected fd8aa9095a95c02dcc35540a263267c29b8fda9d to before f1bcac367bc95631afbb918348f30dec887d0e1bAffected fd8aa9095a95c02dcc35540a263267c29b8fda9d to before 4d260a5558df4650eb87bc41b2c9ac2d6b2ba447Affected fd8aa9095a95c02dcc35540a263267c29b8fda9d to before 8b02f85e84dc6f7c150cef40ddb69af5a25659e5Affected fd8aa9095a95c02dcc35540a263267c29b8fda9d to before cbfaf46b88a4c01b64c4186cdccd766c19ae644cAffected fd8aa9095a95c02dcc35540a263267c29b8fda9d to before 8e9c8a0393b5f85f1820c565ab8105660f4e8f92Affected fd8aa9095a95c02dcc35540a263267c29b8fda9d to before 2466b0f66795c3c426cacc8998499f38031dbb59Affected fd8aa9095a95c02dcc35540a263267c29b8fda9d to before 1f0304dfd9d217c2f8b04a9ef4b3258a66eedd27Affected
LinuxLinux	4.11Affected before 4.11Not affected 5.4.294 through 5.4.Not affected 5.10.238 through 5.10.Not affected 5.15.183 through 5.15.Not affected 6.1.139 through 6.1.Not affected 6.6.91 through 6.6.Not affected 6.12.29 through 6.12.Not affected 6.14.7 through 6.14.*Not affected 6.15 and laterNot affected

Product

Versions

LinuxLinux

fd8aa9095a95c02dcc35540a263267c29b8fda9d to before 0e94a246bb6d9538010b6c02d2b1d4717a97b2e5Affected
fd8aa9095a95c02dcc35540a263267c29b8fda9d to before f1bcac367bc95631afbb918348f30dec887d0e1bAffected
fd8aa9095a95c02dcc35540a263267c29b8fda9d to before 4d260a5558df4650eb87bc41b2c9ac2d6b2ba447Affected
fd8aa9095a95c02dcc35540a263267c29b8fda9d to before 8b02f85e84dc6f7c150cef40ddb69af5a25659e5Affected
fd8aa9095a95c02dcc35540a263267c29b8fda9d to before cbfaf46b88a4c01b64c4186cdccd766c19ae644cAffected
fd8aa9095a95c02dcc35540a263267c29b8fda9d to before 8e9c8a0393b5f85f1820c565ab8105660f4e8f92Affected
fd8aa9095a95c02dcc35540a263267c29b8fda9d to before 2466b0f66795c3c426cacc8998499f38031dbb59Affected
fd8aa9095a95c02dcc35540a263267c29b8fda9d to before 1f0304dfd9d217c2f8b04a9ef4b3258a66eedd27Affected

LinuxLinux

4.11Affected
before 4.11Not affected
5.4.294 through 5.4.*Not affected
5.10.238 through 5.10.*Not affected
5.15.183 through 5.15.*Not affected
6.1.139 through 6.1.*Not affected
6.6.91 through 6.6.*Not affected
6.12.29 through 6.12.*Not affected
6.14.7 through 6.14.*Not affected
6.15 and laterNot affected

References

Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.