6.17-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Gleixner tglx@linutronix.de
commit 6eb350a2233100a283f882c023e5ad426d0ed63b upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/rseq.h | 11 ++++++++--- kernel/rseq.c | 10 +++++----- 2 files changed, 13 insertions(+), 8 deletions(-)
--- a/include/linux/rseq.h +++ b/include/linux/rseq.h @@ -7,6 +7,12 @@ #include <linux/preempt.h> #include <linux/sched.h>
+#ifdef CONFIG_MEMBARRIER +# define RSEQ_EVENT_GUARD irq +#else +# define RSEQ_EVENT_GUARD preempt +#endif + /* * Map the event mask on the user-space ABI enum rseq_cs_flags * for direct mask checks. @@ -41,9 +47,8 @@ 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 @@ -342,12 +342,12 @@ 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; }