pps: Don't crash the machine when exiting will do

PPS is not really the must-have subsystem that warrants crashing
the machine if the ldisc interface is broken.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: George Spelvin <linux@horizon.com>
Acked-by: Rodolfo Giometti <giometti@enneenne.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/drivers/pps/clients/pps-ldisc.c b/drivers/pps/clients/pps-ldisc.c
index 60cee9e0ecb3..a94f73e1480d 100644
--- a/drivers/pps/clients/pps-ldisc.c
+++ b/drivers/pps/clients/pps-ldisc.c
@@ -25,6 +25,7 @@
 #include <linux/serial_core.h>
 #include <linux/tty.h>
 #include <linux/pps_kernel.h>
+#include <linux/bug.h>
 
 #define PPS_TTY_MAGIC           0x0001
 
@@ -33,7 +34,12 @@ static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status,
 {
         struct pps_device *pps = pps_lookup_dev(tty);
 
-        BUG_ON(pps == NULL);
+        /*
+         * This should never fail, but the ldisc locking is very
+         * convoluted, so don't crash just in case.
+         */
+        if (WARN_ON_ONCE(pps == NULL))
+                return;
 
         /* Now do the PPS event report */
         pps_event(pps, ts, status ? PPS_CAPTUREASSERT :
@@ -93,6 +99,9 @@ static void pps_tty_close(struct tty_struct *tty)
 
         alias_n_tty_close(tty);
 
+        if (WARN_ON(!pps))
+                return;
+
         dev_info(pps->dev, "removed\n");
         pps_unregister_source(pps);
 }