Commit-ID: f96f56780ca584930bb3a2769d73fd9a101bcbbe Gitweb: http://git.kernel.org/tip/f96f56780ca584930bb3a2769d73fd9a101bcbbe Author: Masami Hiramatsu <[email protected]> AuthorDate: Mon, 4 Aug 2014 03:10:16 +0000 Committer: Ingo Molnar <[email protected]> CommitDate: Fri, 8 Aug 2014 10:38:04 +0200
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 <[email protected]> Acked-by: Ananth N Mavinakayanahalli <[email protected]> Cc: David S. Miller <[email protected]> Link: http://lkml.kernel.org/r/[email protected] [ Minor edits for clarity. ] Signed-off-by: Ingo Molnar <[email protected]> --- kernel/kprobes.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 734e9a7..3995f54 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -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)) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
