CVE-2026-80777

Summary

In the Linux kernel, the following vulnerability has been resolved:

futex/pi: Plug private futex exec() race

The check for private futexes whether the waiter's mm, which is stored in the futex_key and copied into the pi_state, is the same as the owner's mm is not sufficient for exec(). exec() has a gap where the mm check fails to give the correct answer:

exec() … exec_release_mm() futex_exec_release() tsk::futex::exit_state = EXITING; cleanup_robust_list();

1.  tsk::futex::exit_state = OK;
   

   … old_mm = tsk::mm;
2. tsk::mm = ->mm;

Between #1 and #2 the check for the mm is wrong as that mm is about to be swapped out and eventually freed.

Plug this gap by:

1. Setting tsk::futex::exit_state to FUTEX_STATE_DEAD in futex_exec_release()

2. Setting tsk::futex::exit_state to FUTEX_STATE_OK after the mm has been switched.

From a futex point of view the task is dead after it finished the robust list cleanup up to the point where it sets the state to OK again.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/fdf538b2e69653ff740e84042245018e5680cd7b
• https://git.kernel.org/stable/c/0478bc6bf197629fea0331d65b39eeea043c6cf0
• https://git.kernel.org/stable/c/d7944cee62ec6cca1c90780a766960a57d3b4bb8
• https://git.kernel.org/stable/c/c5f0bc9fd1cec4a00400cc727fcde03e0fde17cc

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