Subject: Re: [patch] isdn: make sure strings are null terminated

From: Dan Carpenter <[email-masked]>
Date: Thu, 24 Nov 2011 14:34:56 +0300

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 <[email-masked]>
> > 
> > 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.

regards,
dan carpenter