6.6-stable review patch. If anyone has any objections, please let me know.
------------------
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/sched.h | 11 ++++++++--- kernel/rseq.c | 10 +++++----- 2 files changed, 13 insertions(+), 8 deletions(-)
--- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2343,6 +2343,12 @@ 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) @@ -2361,9 +2367,8 @@ static inline void rseq_handle_notify_re 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); }
--- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -255,12 +255,12 @@ static int rseq_need_restart(struct task
/* * 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; }