linux-kernel - [PATCH -tip V5 3/4] kprobes: Fix to protect kick_kprobe_optimizer() by kprobe

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Date:   Thu,  2 Apr 2020 22:41:02 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Anders Roxell <anders.roxell@...aro.org>, paulmck@...nel.org,
        joel@...lfernandes.org,
        "Naveen N . Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        David Miller <davem@...emloft.net>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...e.hu>
Subject: [PATCH -tip V5 3/4] kprobes: Fix to protect kick_kprobe_optimizer() by kprobe_mutex

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.

Fixes: cd7ebe2298ff ("kprobes: Use text_poke_smp_batch for optimizing")
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Cc: stable@...r.kernel.org
---
  Changes in v5: Add Fixes and Cc:stable tags.
---
 kernel/kprobes.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 38d9a5d7c8a4..6d76a6e3e1a5 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -592,11 +592,12 @@ static void kprobe_optimizer(struct work_struct *work)
 	mutex_unlock(&module_mutex);
 	mutex_unlock(&text_mutex);
 	cpus_read_unlock();
-	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 */