linux-kernel - [PATCH AUTOSEL 4.9 2/9] Input: mousedev - add a schedule point in mousedev

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Message-Id: <20181022102133.41222-2-sashal@kernel.org>
Date:   Mon, 22 Oct 2018 06:21:26 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.9 2/9] Input: mousedev - add a schedule point in mousedev_write()

From: Eric Dumazet <edumazet@...gle.com>

[ Upstream commit f74c371fe72a4f820d287db8067683fb533e4ede ]

syzbot was able to trigger rcu stalls by calling write()
with large number of bytes.

Add a cond_resched() in the loop to avoid this.

Link: https://lkml.org/lkml/2018/8/23/1106
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: syzbot+9436b02171ac0894d33e@...kaller.appspotmail.com
Reviewed-by: Paul E. McKenney <paulmck@...ux.ibm.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/input/mousedev.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/input/mousedev.c b/drivers/input/mousedev.c
index 30328e57fdda..b63eec7972e6 100644
--- a/drivers/input/mousedev.c
+++ b/drivers/input/mousedev.c
@@ -707,6 +707,7 @@ static ssize_t mousedev_write(struct file *file, const char __user *buffer,
 		mousedev_generate_response(client, c);
 
 		spin_unlock_irq(&client->packet_lock);
+		cond_resched();
 	}
 
 	kill_fasync(&client->fasync, SIGIO, POLL_IN);
-- 
2.17.1