From: Thomas Gleixner tglx@linutronix.de
[ Upstream commit 6eb350a2233100a283f882c023e5ad426d0ed63b ]
rseq_need_restart() reads and clears task::rseq_event_mask with preemption disabled to guard against the scheduler.
But membarrier() uses an IPI and sets the PREEMPT bit in the event mask from the IPI, which leaves that RMW operation unprotected.
Use guard(irq) if CONFIG_MEMBARRIER is enabled to fix that.
Fixes: 2a36ab717e8f ("rseq/membarrier: Add MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ") Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Boqun Feng boqun.feng@gmail.com Reviewed-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: stable@vger.kernel.org [ Applied changes to include/linux/sched.h instead of include/linux/rseq.h ] Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/sched.h | 11 ++++++++--- kernel/rseq.c | 10 +++++----- 2 files changed, 13 insertions(+), 8 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h index 4dc764f3d26f5..37ee1b1c9ed5f 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2313,6 +2313,12 @@ enum rseq_event_mask { RSEQ_EVENT_MIGRATE = (1U << RSEQ_EVENT_MIGRATE_BIT), };
+#ifdef CONFIG_MEMBARRIER +# define RSEQ_EVENT_GUARD irq +#else +# define RSEQ_EVENT_GUARD preempt +#endif + static inline void rseq_set_notify_resume(struct task_struct *t) { if (t->rseq) @@ -2331,9 +2337,8 @@ static inline void rseq_handle_notify_resume(struct ksignal *ksig, static inline void rseq_signal_deliver(struct ksignal *ksig, struct pt_regs *regs) { - preempt_disable(); - __set_bit(RSEQ_EVENT_SIGNAL_BIT, ¤t->rseq_event_mask); - preempt_enable(); + scoped_guard(RSEQ_EVENT_GUARD) + __set_bit(RSEQ_EVENT_SIGNAL_BIT, ¤t->rseq_event_mask); rseq_handle_notify_resume(ksig, regs); }
diff --git a/kernel/rseq.c b/kernel/rseq.c index 840927ac417b1..2fea2782e1799 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -226,12 +226,12 @@ static int rseq_need_restart(struct task_struct *t, u32 cs_flags)
/* * Load and clear event mask atomically with respect to - * scheduler preemption. + * scheduler preemption and membarrier IPIs. */ - preempt_disable(); - event_mask = t->rseq_event_mask; - t->rseq_event_mask = 0; - preempt_enable(); + scoped_guard(RSEQ_EVENT_GUARD) { + event_mask = t->rseq_event_mask; + t->rseq_event_mask = 0; + }
return !!event_mask; }