From cb81572e8cb50c5fb98b0b962cdfe48fff71fd37 Mon Sep 17 00:00:00 2001 From: Phil Sutter Date: Tue, 23 Jul 2019 15:27:52 +0200 Subject: netfilter: nf_tables: Make nft_meta expression more robust nft_meta_get_eval()'s tendency to bail out setting NFT_BREAK verdict in situations where required data is missing leads to unexpected behaviour with inverted checks like so: | meta iifname != eth0 accept This rule will never match if there is no input interface (or it is not known) which is not intuitive and, what's worse, breaks consistency of iptables-nft with iptables-legacy. Fix this by falling back to placing a value in dreg which never matches (avoiding accidental matches), i.e. zero for interface index and an empty string for interface name. Signed-off-by: Phil Sutter Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nft_meta.c | 16 ++++------------ 1 file changed, 4 insertions(+), 12 deletions(-) (limited to 'net/netfilter') diff --git a/net/netfilter/nft_meta.c b/net/netfilter/nft_meta.c index f1b1d948c07b..f69afb9ff3cb 100644 --- a/net/netfilter/nft_meta.c +++ b/net/netfilter/nft_meta.c @@ -60,24 +60,16 @@ void nft_meta_get_eval(const struct nft_expr *expr, *dest = skb->mark; break; case NFT_META_IIF: - if (in == NULL) - goto err; - *dest = in->ifindex; + *dest = in ? in->ifindex : 0; break; case NFT_META_OIF: - if (out == NULL) - goto err; - *dest = out->ifindex; + *dest = out ? out->ifindex : 0; break; case NFT_META_IIFNAME: - if (in == NULL) - goto err; - strncpy((char *)dest, in->name, IFNAMSIZ); + strncpy((char *)dest, in ? in->name : "", IFNAMSIZ); break; case NFT_META_OIFNAME: - if (out == NULL) - goto err; - strncpy((char *)dest, out->name, IFNAMSIZ); + strncpy((char *)dest, out ? out->name : "", IFNAMSIZ); break; case NFT_META_IIFTYPE: if (in == NULL) -- cgit v1.2.3