CVE-2025-37949

Summary

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

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxfd8aa9095a95c02dcc35540a263267c29b8fda9d < 0e94a246bb6d9538010b6c02d2b1d4717a97b2e5affected
LinuxLinuxfd8aa9095a95c02dcc35540a263267c29b8fda9d < f1bcac367bc95631afbb918348f30dec887d0e1baffected
LinuxLinuxfd8aa9095a95c02dcc35540a263267c29b8fda9d < 4d260a5558df4650eb87bc41b2c9ac2d6b2ba447affected
LinuxLinuxfd8aa9095a95c02dcc35540a263267c29b8fda9d < 8b02f85e84dc6f7c150cef40ddb69af5a25659e5affected
LinuxLinuxfd8aa9095a95c02dcc35540a263267c29b8fda9d < cbfaf46b88a4c01b64c4186cdccd766c19ae644caffected
LinuxLinuxfd8aa9095a95c02dcc35540a263267c29b8fda9d < 8e9c8a0393b5f85f1820c565ab8105660f4e8f92affected
LinuxLinuxfd8aa9095a95c02dcc35540a263267c29b8fda9d < 2466b0f66795c3c426cacc8998499f38031dbb59affected
LinuxLinuxfd8aa9095a95c02dcc35540a263267c29b8fda9d < 1f0304dfd9d217c2f8b04a9ef4b3258a66eedd27affected
LinuxLinux4.11affected
LinuxLinux0 < 4.11unaffected
LinuxLinux5.4.294 <= 5.4.*unaffected
LinuxLinux5.10.238 <= 5.10.*unaffected
LinuxLinux5.15.183 <= 5.15.*unaffected
LinuxLinux6.1.139 <= 6.1.*unaffected
LinuxLinux6.6.91 <= 6.6.*unaffected
LinuxLinux6.12.29 <= 6.12.*unaffected
LinuxLinux6.14.7 <= 6.14.*unaffected
LinuxLinux6.15 <= *unaffected

Weaknesses

ADP Enrichment

CVE Program Container

Additional References

References