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CVE-2025-37949

xenbus: Use kref to track req lifetime

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.4.294, 5.10.238, 5.15.183, 6.1.139, 6.6.91, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

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

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From fd8aa9095a95c02dcc35540a263267c29b8fda9d · fixed in 0e94a246bb6d9538010b6c02d2b1d4717a97b2e5; From fd8aa9095a95c02dcc35540a263267c29b8fda9d · fixed in f1bcac367bc95631afbb918348f30dec887d0e1b; From fd8aa9095a95c02dcc35540a263267c29b8fda9d · fixed in 4d260a5558df4650eb87bc41b2c9ac2d6b2ba447; From fd8aa9095a95c02dcc35540a263267c29b8fda9d · fixed in 8b02f85e84dc6f7c150cef40ddb69af5a25659e5; From fd8aa9095a95c02dcc35540a263267c29b8fda9d · fixed in cbfaf46b88a4c01b64c4186cdccd766c19ae644c; From fd8aa9095a95c02dcc35540a263267c29b8fda9d · fixed in 8e9c8a0393b5f85f1820c565ab8105660f4e8f92; From fd8aa9095a95c02dcc35540a263267c29b8fda9d · fixed in 2466b0f66795c3c426cacc8998499f38031dbb59; From fd8aa9095a95c02dcc35540a263267c29b8fda9d · fixed in 1f0304dfd9d217c2f8b04a9ef4b3258a66eedd27

  • Linux Linux

    4.11

  • KernelLinux

    From 4.11.0 · fixed in 5.4.294; From 5.5.0 · fixed in 5.10.238; From 5.11.0 · fixed in 5.15.183; From 5.16.0 · fixed in 6.1.139; From 6.2.0 · fixed in 6.6.91; From 6.7.0 · fixed in 6.12.29; From 6.13.0 · fixed in 6.14.7

References 8

git.kernel.org