linux-kernel - [PATCH -tip 1/4] kprobes: Lock kprobe_mutex while showing kprobe

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Date:   Thu, 26 Mar 2020 23:49:36 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Paul McKenney <paulmck@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Brian Gerst <brgerst@...il.com>,
        Juergen Gross <jgross@...e.com>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH -tip 1/4] kprobes: Lock kprobe_mutex while showing kprobe_blacklist

Lock kprobe_mutex while showing kprobe_blacklist to prevent
updating the kprobe_blacklist.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 kernel/kprobes.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 2625c241ac00..570d60827656 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2420,6 +2420,7 @@ static const struct file_operations debugfs_kprobes_operations = {
 /* kprobes/blacklist -- shows which functions can not be probed */
 static void *kprobe_blacklist_seq_start(struct seq_file *m, loff_t *pos)
 {
+	mutex_lock(&kprobe_mutex);
 	return seq_list_start(&kprobe_blacklist, *pos);
 }
 
@@ -2446,10 +2447,15 @@ static int kprobe_blacklist_seq_show(struct seq_file *m, void *v)
 	return 0;
 }
 
+static void kprobe_blacklist_seq_stop(struct seq_file *f, void *v)
+{
+	mutex_unlock(&kprobe_mutex);
+}
+
 static const struct seq_operations kprobe_blacklist_seq_ops = {
 	.start = kprobe_blacklist_seq_start,
 	.next  = kprobe_blacklist_seq_next,
-	.stop  = kprobe_seq_stop,	/* Reuse void function */
+	.stop  = kprobe_blacklist_seq_stop,
 	.show  = kprobe_blacklist_seq_show,
 };