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

[Jon Maloy <jmaloy@redhat.com>]

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"

/jon

> +		return -EINVAL;
> +	}
>   	if (new->flags & ~allowed_flags) {
>   		warn("Rule has invalid flags 0x%hhx",
>   		     new->flags & ~allowed_flags);
>   		return -EINVAL;
>   	}
> -	if (new->flags & FWD_DUAL_STACK_ANY &&
> -	    !inany_equals(&new->addr, &inany_any6)) {
> -		char astr[INANY_ADDRSTRLEN];
> +	if (new->flags & FWD_DUAL_STACK_ANY) {
> +		if (!inany_equals(&new->addr, &inany_any6)) {
> +			char astr[INANY_ADDRSTRLEN];
>   
> -		warn("Dual stack rule has non-wildcard address %s",
> -		     inany_ntop(&new->addr, astr, sizeof(astr)));
> +			warn("Dual stack rule has non-wildcard address %s",
> +			     inany_ntop(&new->addr, astr, sizeof(astr)));
> +			return -EINVAL;
> +		}
> +		if (!(fwd->caps & FWD_CAP_IPV4)) {
> +			warn("Dual stack forward, but IPv4 not enabled");
> +			return -EINVAL;
> +		}
> +		if (!(fwd->caps & FWD_CAP_IPV6)) {
> +			warn("Dual stack forward, but IPv6 not enabled");
> +			return -EINVAL;
> +		}
> +	} else {
> +		if (inany_v4(&new->addr) && !(fwd->caps & FWD_CAP_IPV4)) {
> +			warn("IPv4 forward, but IPv4 not enabled");
> +			return -EINVAL;
> +		}
> +		if (!inany_v4(&new->addr) && !(fwd->caps & FWD_CAP_IPV6)) {
> +			warn("IPv6 forward, but IPv6 not enabled");
> +			return -EINVAL;
> +		}
> +	}
> +	if (new->proto == IPPROTO_TCP) {
> +		if (!(fwd->caps & FWD_CAP_TCP)) {
> +			warn("Can't add TCP forwarding rule, TCP not enabled");
> +			return -EINVAL;
> +		}
> +	} else if (new->proto == IPPROTO_UDP) {
> +		if (!(fwd->caps & FWD_CAP_UDP)) {
> +			warn("Can't add UDP forwarding rule, UDP not enabled");
> +			return -EINVAL;
> +		}
> +	} else {
> +		warn("Unsupported protocol 0x%hhx (%s) for forwarding rule",
> +		     new->proto, ipproto_name(new->proto));
>   		return -EINVAL;
>   	}
>