pps: do not crash when failed to register
With this command sequence:
modprobe plip
modprobe pps_parport
rmmod pps_parport
the partport_pps modules causes this crash:
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: parport_detach+0x1d/0x60 [pps_parport]
Oops: 0000 [#1] SMP
...
Call Trace:
parport_unregister_driver+0x65/0xc0 [parport]
SyS_delete_module+0x187/0x210
The sequence that builds up to this is:
1) plip is loaded and takes the parport device for exclusive use:
plip0: Parallel port at 0x378, using IRQ 7.
2) pps_parport then fails to grab the device:
pps_parport: parallel port PPS client
parport0: cannot grant exclusive access for device pps_parport
pps_parport: couldn't register with parport0
3) rmmod of pps_parport is then killed because it tries to access
pardev->name, but pardev (taken from port->cad) is NULL.
So add a check for NULL in the test there too.
Link: http://lkml.kernel.org/r/20160714115245.12651-1-jslaby@suse.cz
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Rodolfo Giometti <giometti@enneenne.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/pps/clients/pps_parport.c b/drivers/pps/clients/pps_parport.c
index 38a8bbe..83797d8 100644
--- a/drivers/pps/clients/pps_parport.c
+++ b/drivers/pps/clients/pps_parport.c
@@ -195,7 +195,7 @@
struct pps_client_pp *device;
/* FIXME: oooh, this is ugly! */
- if (strcmp(pardev->name, KBUILD_MODNAME))
+ if (!pardev || strcmp(pardev->name, KBUILD_MODNAME))
/* not our port */
return;
