diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2021-02-01 15:12:10 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-02-03 23:16:16 +0100 |
| commit | 6eaebabf3bca8ff10ca5542c3d3d72ad829db934 (patch) | |
| tree | 26e847f4594dd66a3b87221f00246a64df1d105c /kernel | |
| parent | 40da511f787b75a80efa3ae5d3f90753a795a9e4 (diff) | |
futex: Sanitize exit state handling
commit 4a8e991b91aca9e20705d434677ac013974e0e30 upstream.
Instead of having a smp_mb() and an empty lock/unlock of task::pi_lock move
the state setting into to the lock section.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191106224556.645603214@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/futex.c | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index 5bd3afee4e13..0efcb55455c2 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -3276,16 +3276,19 @@ void futex_exit_recursive(struct task_struct *tsk) void futex_exit_release(struct task_struct *tsk) { - tsk->futex_state = FUTEX_STATE_EXITING; - /* - * Ensure that all new tsk->pi_lock acquisitions must observe - * FUTEX_STATE_EXITING. Serializes against attach_to_pi_owner(). - */ - smp_mb(); /* - * Ensure that we must observe the pi_state in exit_pi_state_list(). + * Switch the state to FUTEX_STATE_EXITING under tsk->pi_lock. + * + * This ensures that all subsequent checks of tsk->futex_state in + * attach_to_pi_owner() must observe FUTEX_STATE_EXITING with + * tsk->pi_lock held. + * + * It guarantees also that a pi_state which was queued right before + * the state change under tsk->pi_lock by a concurrent waiter must + * be observed in exit_pi_state_list(). */ raw_spin_lock_irq(&tsk->pi_lock); + tsk->futex_state = FUTEX_STATE_EXITING; raw_spin_unlock_irq(&tsk->pi_lock); futex_exec_release(tsk); |