[PATCH] pSeries hvsi char driver null pointer deref

Under certain rare circumstances, it appears that there can be be a
NULL-pointer deref when a user fiddles with terminal emeulation programs while
outpu is being sent to the console.  This patch checks for and avoids a
NULL-pointer deref.

Signed-off-by: Hollis Blanchard <hollisbl@austin.ibm.com>
Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: Paul Fulghum <paulkf@microgate.com>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/char/hvsi.c b/drivers/char/hvsi.c
index 41db8060e8f7..54cbb58b8740 100644
--- a/drivers/char/hvsi.c
+++ b/drivers/char/hvsi.c
@@ -311,7 +311,8 @@ static void hvsi_recv_control(struct hvsi_struct *hp, uint8_t *packet,
                                 /* CD went away; no more connection */
                                 pr_debug("hvsi%i: CD dropped\n", hp->index);
                                 hp->mctrl &= TIOCM_CD;
-                                if (!(hp->tty->flags & CLOCAL))
+                                /* If userland hasn't done an open(2) yet, hp->tty is NULL. */
+                                if (hp->tty && !(hp->tty->flags & CLOCAL))
                                         *to_hangup = hp->tty;
                         }
                         break;