Re: [PATCH] tty/n_hdlc: fix __might_sleep warning

[Arnd Bergmann]

On Thu, Jan 10, 2019 at 12:39 PM Tetsuo Handa
 wrote:
> On 2019/01/02 5:28, Paul Fulghum wrote:
> > Fix __might_sleep warning in tty/n_hdlc.c read due to copy_to_user call 
> > while current is TASK_INTERRUPTIBLE.
> > This is a false positive since the code path does not depend on current 
> > state remaining TASK_INTERRUPTIBLE.
> > The loop breaks out and sets TASK_RUNNING after calling copy_to_user.
> > This patch supresses the warning by setting TASK_RUNNING before calling 
> > copy_to_user.
> >
> > [1] 
> > https://syzkaller.appspot.com/bug?id=17d5de7f1fcab794cb8c40032f893f52de899324
> >
> > Signed-off-by: Paul Fulghum 
> > Reported-by: syzbot 
> > Cc: Greg Kroah-Hartman 
> > Cc: Tetsuo Handa 
> > Cc: Arnd Bergmann 
> > Cc: Alan Cox 

This version looks good to me.

Acked-by: Arnd Bergmann 

   Arnd

Re: [PATCH] tty/n_hdlc: fix __might_sleep warning

[Tetsuo Handa]

Hello, Greg.

We attempted a cleanup but we failed. Thus, will you apply this patch for now?

On 2019/01/02 5:28, Paul Fulghum wrote:
> Fix __might_sleep warning in tty/n_hdlc.c read due to copy_to_user call while 
> current is TASK_INTERRUPTIBLE.
> This is a false positive since the code path does not depend on current state 
> remaining TASK_INTERRUPTIBLE.
> The loop breaks out and sets TASK_RUNNING after calling copy_to_user. 
> This patch supresses the warning by setting TASK_RUNNING before calling 
> copy_to_user.
> 
> [1] 
> https://syzkaller.appspot.com/bug?id=17d5de7f1fcab794cb8c40032f893f52de899324
> 
> Signed-off-by: Paul Fulghum 
> Reported-by: syzbot 
> Cc: Greg Kroah-Hartman 
> Cc: Tetsuo Handa 
> Cc: Arnd Bergmann 
> Cc: Alan Cox 
> —
> --- a/drivers/tty/n_hdlc.c2018-12-23 15:55:59.0 -0800
> +++ b/drivers/tty/n_hdlc.c2019-01-01 11:44:47.148153954 -0800
> @@ -597,6 +597,7 @@ static ssize_t n_hdlc_tty_read(struct tt
>   /* too large for caller's buffer */
>   ret = -EOVERFLOW;
>   } else {
> + __set_current_state(TASK_RUNNING);
>   if (copy_to_user(buf, rbuf->buf, rbuf->count))
>   ret = -EFAULT;
>   else

[PATCH] tty/n_hdlc: fix __might_sleep warning

[Paul Fulghum]

Fix __might_sleep warning in tty/n_hdlc.c read due to copy_to_user call while 
current is TASK_INTERRUPTIBLE.
This is a false positive since the code path does not depend on current state 
remaining TASK_INTERRUPTIBLE.
The loop breaks out and sets TASK_RUNNING after calling copy_to_user. 
This patch supresses the warning by setting TASK_RUNNING before calling 
copy_to_user.

[1] 
https://syzkaller.appspot.com/bug?id=17d5de7f1fcab794cb8c40032f893f52de899324

Signed-off-by: Paul Fulghum 
Reported-by: syzbot 
Cc: Greg Kroah-Hartman 
Cc: Tetsuo Handa 
Cc: Arnd Bergmann 
Cc: Alan Cox 
—
--- a/drivers/tty/n_hdlc.c  2018-12-23 15:55:59.0 -0800
+++ b/drivers/tty/n_hdlc.c  2019-01-01 11:44:47.148153954 -0800
@@ -597,6 +597,7 @@ static ssize_t n_hdlc_tty_read(struct tt
/* too large for caller's buffer */
ret = -EOVERFLOW;
} else {
+   __set_current_state(TASK_RUNNING);
if (copy_to_user(buf, rbuf->buf, rbuf->count))
ret = -EFAULT;
else