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Subject: Re: [PATCH] tty/n_hdlc: fix __might_sleep warning
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>, jslaby@suse.com
Cc:     Paul Fulghum <paulkf@microgate.com>,
        "linux-kernel@vger.kernel.org Mailing List" 
        <linux-kernel@vger.kernel.org>, Arnd Bergmann <arnd@arndb.de>,
        Alan Cox <alan@lxorguk.ukuu.org.uk>,
        syzbot <syzbot+c244af085a0159d22879@syzkaller.appspotmail.com>,
        syzkaller-bugs@googlegroups.com
References: <000000000000449587057e1e6f8b@google.com>
 <49b3b189-a51f-6a97-0e1f-bc3f2c305299@I-love.SAKURA.ne.jp>
 <62FAC6A3-AC41-44CD-8ABC-79F404BF8CB1@microgate.com>
 <F23DE81F-C976-4AED-8990-84A6ADC1BF1F@microgate.com>
From:   Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Message-ID: <d351e662-0087-9cd7-46b2-ef49134c639c@i-love.sakura.ne.jp>
Date:   Thu, 10 Jan 2019 20:38:33 +0900
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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 <paulkf@microgate.com>
> Reported-by: syzbot <syzbot+c244af085a0159d22879@syzkaller.appspotmail.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
> —
> --- a/drivers/tty/n_hdlc.c	2018-12-23 15:55:59.000000000 -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