[PATCH] kprobes: bugfix: force unoptimize when disable kprobes.

From: Wang Nan
Date: Mon Jan 05 2015 - 07:38:20 EST


Original code failed to disarm the probed instruction after

echo 0 > /sys/kernel/debug/kprobes/enabled

if OPTPROBE is enabled.

This is caused by a piece of logically inconsistent code:

unoptimize_kprobe(p, false);
if (!kprobe_queued(p)) {
...
}

unoptimize_kprobe() with 'force' == false queues p onto
unoptimizing_list, so following kprobe_queued() check always fail unless
another core schedules optimizer and does the unoptimization very soon.
This logic causes arch_disarm_kprobe() failed to get execute, lefts a
breakpoint at the probed address, instead of restoring it.

This patch uses force unoptimize instead.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
---
kernel/kprobes.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index b185464..9fbe0c3 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -869,7 +869,7 @@ static void __disarm_kprobe(struct kprobe *p, bool reopt)
{
struct kprobe *_p;

- unoptimize_kprobe(p, false); /* Try to unoptimize */
+ unoptimize_kprobe(p, true); /* Try to unoptimize */

if (!kprobe_queued(p)) {
arch_disarm_kprobe(p);
--
1.8.4

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