linux-kernel - [PATCH 3.16 054/202] tty/n_hdlc: fix __might

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Date:   Sat, 27 Apr 2019 16:13:09 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "syzbot" <syzbot+c244af085a0159d22879@...kaller.appspotmail.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Paul Fulghum" <paulkf@...rogate.com>,
        "Arnd Bergmann" <arnd@...db.de>,
        "Tetsuo Handa" <penguin-kernel@...ove.SAKURA.ne.jp>,
        "Alan Cox" <alan@...rguk.ukuu.org.uk>
Subject: [PATCH 3.16 054/202] tty/n_hdlc: fix __might_sleep warning

3.16.66-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Paul Fulghum <paulkf@...rogate.com>

commit fc01d8c61ce02c034e67378cd3e645734bc18c8c upstream.

Fix __might_sleep warning[1] 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@...rogate.com>
Reported-by: syzbot <syzbot+c244af085a0159d22879@...kaller.appspotmail.com>
Cc: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>
Acked-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/tty/n_hdlc.c | 1 +
 1 file changed, 1 insertion(+)

--- a/drivers/tty/n_hdlc.c
+++ b/drivers/tty/n_hdlc.c
@@ -598,6 +598,7 @@ 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