futex/pi: Plug private futex exec() race

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.

Timeline

1. Sep 4, 2026, 3:12 PM UTCCVE published
2. Oct 19, 2026, 8:43 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 80367ad01d93ac781b0e1df246edaf006928002f · fixed in fdf538b2e69653ff740e84042245018e5680cd7b; From 80367ad01d93ac781b0e1df246edaf006928002f · fixed in 0478bc6bf197629fea0331d65b39eeea043c6cf0; From 80367ad01d93ac781b0e1df246edaf006928002f · fixed in d7944cee62ec6cca1c90780a766960a57d3b4bb8; From 80367ad01d93ac781b0e1df246edaf006928002f · fixed in c5f0bc9fd1cec4a00400cc727fcde03e0fde17cc

• Linux Linux

  6.16

• KernelLinux

  From 6.16.0 · fixed in 6.18.47; From 6.19.0 · fixed in 7.1.11; From 7.2.0 · fixed in 7.2.1

References 4