On Thu, Nov 24, 2011 at 01:21:42PM +0100, walter harms wrote: > > > Am 24.11.2011 12:34, schrieb Dan Carpenter: > > On Wed, Nov 23, 2011 at 09:25:56AM +0100, walter harms wrote: > >> > >> > >> Am 23.11.2011 07:42, schrieb Dan Carpenter: > >>> These strings come from the user. We strcpy() them inside > >>> cf_command() so we should check that they are NULL terminated and > >>> return an error if not. > >>> > >>> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> > >>> > >>> diff --git a/drivers/isdn/divert/divert_procfs.c b/drivers/isdn/divert/divert_procfs.c > >>> index 33ec9e4..0c16687 100644 > >>> --- a/drivers/isdn/divert/divert_procfs.c > >>> +++ b/drivers/isdn/divert/divert_procfs.c > >>> @@ -242,6 +242,10 @@ static int isdn_divert_ioctl_unlocked(struct file *file, uint cmd, ulong arg) > >>> case IIOCDOCFINT: > >>> if (!divert_if.drv_to_name(dioctl.cf_ctrl.drvid)) > >>> return (-EINVAL); /* invalid driver */ > >>> + if (strlen(dioctl.cf_ctrl.msn) >= sizeof(dioctl.cf_ctrl.msn)) > >>> + return -EINVAL; > >>> + if (strlen(dioctl.cf_ctrl.fwd_nr) >= sizeof(dioctl.cf_ctrl.fwd_nr)) > >>> + return -EINVAL; > >> > >> forcing the last field to be zero seems more easy. > >> dioctl.cf_ctrl.fwd_nr[sizeof(dioctl.cf_ctrl.fwd_nr))-1]=0; > >> > > > > That's a valid option to use, but I'd prefer to return an error code > > here because that's what we do on the line before. Passing a too > > long string is clearly invalid. > > > > the line before has the same problem, of cause. > > So far i see you do not get a string, you get a structure. An it will hard > to validate the element is a useful string. I thing my (sledgehammer) method > is ok here because you make sure that all later calls (strcmp,strcpy) will succeed. > If someone supplies a bad string the later calls will catch by failing to identify > and return a proper code from there (at least i hope so). > Since the proper userspace programs should use the correct size, these valid fixes (Thanks !) will prevent bad programs to use this for some bad purpose. I think both methods are OK, I tend to the sledgehammer, because it is the lowest CPU consuming method - but on the other side the valid length is small enough. Thanks Karsten -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
