Skip kretprobe hit in NMI context, because if an NMI happens
inside the critical section protected by kretprobe_table.lock
and another(or same) kretprobe hit, pre_kretprobe_handler
tries to lock kretprobe_table.lock again.
Normal interrupts have no problem because they are disabled
with the lock.
Changes in v2:
- Add unlikely for in_nmi.
- Add a comment for nmissed counter.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
Acked-by: Ananth N Mavinakayanahalli <ana...@in.ibm.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: "David S. Miller" <da...@davemloft.net>
---
kernel/kprobes.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 734e9a7..138219b 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1778,6 +1778,16 @@ static int pre_handler_kretprobe(struct kprobe *p,
struct pt_regs *regs)
unsigned long hash, flags = 0;
struct kretprobe_instance *ri;
+ /* To avoid deadlock, prohibit return probing in NMI context */
+ if (unlikely(in_nmi())) {
+ /*
+ * Do not get a lock. nmissed is not accurate.
+ * This just informs user some misses are happened.
+ */
+ rp->nmissed++;
+ return 0;
+ }
+
/*TODO: consider to only swap the RA after the last pre_handler fired */
hash = hash_ptr(current, KPROBE_HASH_BITS);
raw_spin_lock_irqsave(&rp->lock, flags);
--
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