Re: [PATCH v5 01/18] conf, fwd: Stricter rule checking in fwd_rule_add()

[Stefano Brivio <sbrivio@redhat.com>]

On Sun, 26 Apr 2026 11:31:24 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> On Sat, Apr 25, 2026 at 11:31:40AM -0400, Jon Maloy wrote:
> > 
> > 
> > On 2026-04-21 02:24, David Gibson wrote:  
> > > Although fwd_rule_add() performs some sanity checks on the rule it is
> > > given, there are invalid rules we don't check for, assuming that its
> > > callers will do that.
> > >   
> >   
> > > diff --git a/fwd.c b/fwd.c
> > > index c7fd1a9d..979c1494 100644
> > > --- a/fwd.c
> > > +++ b/fwd.c
> > > @@ -367,17 +367,59 @@ int fwd_rule_add(struct fwd_table *fwd, const struct fwd_rule *new)
> > >   		     new->first, new->last);
> > >   		return -EINVAL;
> > >   	}
> > > +	if (!new->first) {
> > > +		warn("Forwarding rule attempts to map from port 0");
> > > +		return -EINVAL;
> > > +	}
> > > +	if (!new->to ||
> > > +	    (in_port_t)(new->to + new->last - new->first) < new->to) {
> > > +		warn("Forwarding rule attempts to map to port 0");  
> > 
> > Not strictly true. We are also catching a range overflow case.
> > Maybe "Forwarding rule maps to invalid port number"  
> 
> Well.. the specific overflow case is that the target range "wraps
> around", thereby covering port 0, is the reasoning here.

...and any other range overflow case is covered by the earlier check:

	if (new->first > new->last) {
		warn("Rule has invalid port range %u-%u",
		     new->first, new->last);
		return -EINVAL;
	}

so I'm leaving this as it was, in v6.

-- 
Stefano