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.
Unified · Split
| @@ -195,7 +195,7 @@ static void parport_detach(struct parport *port) · 194 unmodified lines | ||
| 195 | 195 | struct pps_client_pp *device; |
| 196 | 196 | |
| 197 | 197 | /* FIXME: oooh, this is ugly! */ |
| 198 | − if (strcmp(pardev->name, KBUILD_MODNAME)) | |
| 198 | + if (!pardev || strcmp(pardev->name, KBUILD_MODNAME)) | |
| 199 | 199 | /* not our port */ |
| 200 | 200 | return; |
| 201 | 201 | |