From: Jiri Slaby Date: Wed, 20 Jul 2016 22:45:08 +0000 (-0700) Subject: pps: do not crash when failed to register X-Git-Tag: firefly_0821_release~176^2~4^2~36^2~53 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=78edebc495bbd8e3c2cced6a937467140a4fd52b;p=firefly-linux-kernel-4.4.55.git 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] 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 Acked-by: Rodolfo Giometti Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/pps/clients/pps_parport.c b/drivers/pps/clients/pps_parport.c index 38a8bbe74810..83797d89c30f 100644 --- a/drivers/pps/clients/pps_parport.c +++ b/drivers/pps/clients/pps_parport.c @@ -195,7 +195,7 @@ static void parport_detach(struct parport *port) 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;