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kprobes: Skip kretprobe hit in NMI context to avoid deadlock

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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>
This commit is contained in:
Masami Hiramatsu 2014-08-04 03:10:16 +00:00 committed by Ingo Molnar
parent 98a96f2022
commit f96f56780c
1 changed files with 12 additions and 1 deletions
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13
kernel/kprobes.c
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@ -1778,7 +1778,18 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
unsigned long hash, flags = 0;
struct kretprobe_instance *ri;
/*TODO: consider to only swap the RA after the last pre_handler fired */
/*
* 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);
if (!hlist_empty(&rp->free_instances)) {