Don't forget to relock the TTY after uiomove() returns an error.

Peter Holm just discovered this funny bug inside the TTY code: if
uiomove() in ttydisc_write() returns an error, we forget to relock the
TTY before jumping out of ttydisc_write(). Fix it by placing
tty_unlock() and tty_lock() around uiomove().

Submitted by:	pho

1 files changed, 2 insertions, 4 deletions

diff --git a/sys/kern/tty_ttydisc.c b/sys/kern/tty_ttydisc.c
index 0d7dd7f..800ad13 100644
--- a/sys/kern/tty_ttydisc.c
+++ b/sys/kern/tty_ttydisc.c
@@ -460,17 +460,15 @@ ttydisc_write(struct tty *tp, struct uio *uio, int ioflag)
 		MPASS(oblen == 0);
 
 		/* Step 1: read data. */
-
-		tty_unlock(tp);
-
 		obstart = ob;
 		nlen = MIN(uio->uio_resid, sizeof ob);
+		tty_unlock(tp);
 		error = uiomove(ob, nlen, uio);
+		tty_lock(tp);
 		if (error != 0)
 			break;
 		oblen = nlen;
 
-		tty_lock(tp);
 		if (tty_gone(tp)) {
 			error = ENXIO;
 			break;