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

[David Gibson <david@gibson.dropbear.id.au>]

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On Sun, May 03, 2026 at 11:56:08PM +0200, Stefano Brivio wrote:
> 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.

Right, that's pretty much what I was suggesting.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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