linux-kernel - [PATCH 4.9 21/44] tty/n_hdlc: fix __might

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Date:   Tue, 29 Jan 2019 12:36:16 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Paul Fulghum <paulkf@...rogate.com>,
        syzbot <syzbot+c244af085a0159d22879@...kaller.appspotmail.com>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Alan Cox <alan@...rguk.ukuu.org.uk>,
        Arnd Bergmann <arnd@...db.de>
Subject: [PATCH 4.9 21/44] tty/n_hdlc: fix __might_sleep warning

4.9-stable 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>
Cc: stable <stable@...r.kernel.org>
Acked-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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