blob: cbb3c5172684932d1978a0c8fd39c29c93e0c360 [file] [log] [blame]
From: Jiri Slaby <>
Date: Wed, 20 Jul 2016 15:45:08 -0700
Subject: pps: do not crash when failed to register
commit 368301f2fe4b07e5fb71dba3cc566bc59eb6705f upstream.
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]
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.
Signed-off-by: Jiri Slaby <>
Acked-by: Rodolfo Giometti <>
Signed-off-by: Andrew Morton <>
Signed-off-by: Linus Torvalds <>
Signed-off-by: Ben Hutchings <>
drivers/pps/clients/pps_parport.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/pps/clients/pps_parport.c
+++ b/drivers/pps/clients/pps_parport.c
@@ -195,7 +195,7 @@ static void parport_detach(struct parpor
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 */