Input: mousedev - add a schedule point in mousedev_write()

edumazet · dtor · commit f74c371fe72a · 2018-10-04T17:42:26.000-07:00
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@google.com> Reported-by: syzbot+9436b02171ac0894d33e@syzkaller.appspotmail.com Reviewed-by: Paul E. McKenney <paulmck@linux.ibm.com> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
diff --git 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);

Original file line number	Diff line number	Diff line change
`@@ -707,6 +707,7 @@ static ssize_t mousedev_write(struct file file, const char __user buffer,`
`707`	`707`	`mousedev_generate_response(client, c);`
`708`	`708`
`709`	`709`	`spin_unlock_irq(&client->packet_lock);`
	`710`	`+ cond_resched();`
`710`	`711`	`}`
`711`	`712`
`712`	`713`	`kill_fasync(&client->fasync, SIGIO, POLL_IN);`