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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     Masami Hiramatsu <mhiramat@kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        "Gustavo A . R . Silva" <gustavoars@kernel.org>,
        Anders Roxell <anders.roxell@linaro.org>,
        "Naveen N . Rao" <naveen.n.rao@linux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
        David Miller <davem@davemloft.net>,
        Ingo Molnar <mingo@elte.hu>,
        Peter Zijlstra <peterz@infradead.org>,
        Ziqian SUN <zsun@redhat.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.4 070/135] kprobes: Fix to protect kick_kprobe_optimizer() by kprobe_mutex
Date:   Mon, 29 Jun 2020 11:52:04 -0400
Message-Id: <20200629155309.2495516-71-sashal@kernel.org>
In-Reply-To: <20200629155309.2495516-1-sashal@kernel.org>
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From: Masami Hiramatsu <mhiramat@kernel.org>

[ 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@kernel.org>
Cc: "Gustavo A . R . Silva" <gustavoars@kernel.org>
Cc: Anders Roxell <anders.roxell@linaro.org>
Cc: "Naveen N . Rao" <naveen.n.rao@linux.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: David Miller <davem@davemloft.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ziqian SUN <zsun@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/kprobes.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index f59f49bc2a5d5..430baa19e48c3 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