[PATCH 4.9 092/191] kprobes: Fix to protect kick_kprobe_optimizer() by kprobe_mutex

[Sasha Levin]

From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>

[ Upstream commit 1a0aa991a6274161c95a844c58cfb801d681eb59 ]

In kprobe_optimizer() kick_kprobe_optimizer() is called
without kprobe_mutex, but this can race with other caller
which is protected by kprobe_mutex.

To fix that, expand kprobe_mutex protected area to protect
kick_kprobe_optimizer() call.

Link: http://lkml.kernel.org/r/158927057586.27680.5036330063955940456.stgit@devnote2

Fixes: cd7ebe2298ff ("kprobes: Use text_poke_smp_batch for optimizing")
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "Gustavo A . R . Silva" <gustavoars@xxxxxxxxxx>
Cc: Anders Roxell <anders.roxell@xxxxxxxxxx>
Cc: "Naveen N . Rao" <naveen.n.rao@xxxxxxxxxxxxx>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>
Cc: David Miller <davem@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ziqian SUN <zsun@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 kernel/kprobes.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 1b75fb8c7735e..3db9cf412996c 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -561,11 +561,12 @@ static void kprobe_optimizer(struct work_struct *work)
 	do_free_cleaned_kprobes();
 
 	mutex_unlock(&module_mutex);
-	mutex_unlock(&kprobe_mutex);
 
 	/* Step 5: Kick optimizer again if needed */
 	if (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list))
 		kick_kprobe_optimizer();
+
+	mutex_unlock(&kprobe_mutex);
 }
 
 /* Wait for completing optimization and unoptimization */
-- 
2.25.1