[PATCH 4.4 16/65] tty/n_hdlc: fix __might_sleep warning

From: Greg Kroah-Hartman
Date: Mon Feb 04 2019 - 06:11:01 EST

4.4-stable review patch. If anyone has any objections, please let me know.


From: Paul Fulghum <paulkf@xxxxxxxxxxxxx>

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

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

Signed-off-by: Paul Fulghum <paulkf@xxxxxxxxxxxxx>
Reported-by: syzbot <syzbot+c244af085a0159d22879@xxxxxxxxxxxxxxxxxxxxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Acked-by: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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 */
} else {
+ __set_current_state(TASK_RUNNING);
if (copy_to_user(buf, rbuf->buf, rbuf->count))
ret = -EFAULT;