lkml.org 
[lkml]   [2018]   [Oct]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] Input: mousedev - add a schedule point in mousedev_write()
Hi Eric,

On Thu, Oct 04, 2018 at 08:47:49AM -0700, Eric Dumazet wrote:
> 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.

I think this simply masks a deeper issue. The code fetches characters
from userspace in a loop, takes a lock, quickly places response in an
output buffer, and releases interrupt. I do not see why this should
cause stalls as we do not hold spinlock/interrupts off for extended
period of time.

Adding Paul so he can straighten me out...

>
> Link: https://lkml.org/lkml/2018/8/23/1106
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: syzbot+9436b02171ac0894d33e@syzkaller.appspotmail.com
> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> Cc: linux-input@vger.kernel.org
> ---
> drivers/input/mousedev.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/input/mousedev.c b/drivers/input/mousedev.c
> index e08228061bcdd2f97aaadece31d6c83eb7539ae5..412fa71245afe26a7a8ad75705566f83633ba347 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);
> --
> 2.19.0.605.g01d371f741-goog
>

Thanks.

--
Dmitry

\
 
 \ /
  Last update: 2018-10-04 21:00    [W:0.112 / U:0.340 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site