Commit f96f5678 authored Aug 04, 2014 by Masami Hiramatsu Committed by Ingo Molnar Aug 08, 2014

kprobes: Skip kretprobe hit in NMI context to avoid deadlock



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.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: David S. Miller <davem@davemloft.net>
Link: http://lkml.kernel.org/r/20140804031016.11433.65539.stgit@kbuild-fedora.novalocal


[ Minor edits for clarity. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 98a96f20

kernel/kprobes.c

+12 −1

Original line number	Diff line number	Diff line
		@@ -1778,6 +1778,17 @@ static int pre_handler_kretprobe(struct kprobe p, struct pt_regs regs)
		unsigned long hash, flags = 0;
		struct kretprobe_instance *ri;

		/*
		* To avoid deadlocks, prohibit return probing in NMI contexts,
		* just skip the probe and increase the (inexact) 'nmissed'
		* statistical counter, so that the user is informed that
		* something happened:
		*/
		if (unlikely(in_nmi())) {
		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);