CVE-2026-80777futex/pi: Plug private futex exec() race

Official description

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 packages & fixed versions

Affected products (as reported)

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