xtables: Fix for false-positive rule matching

When comparing two rules with non-standard targets, differences in
targets' payloads wasn't respected.

The cause is a rather hideous one: Unlike xtables_find_match(),
xtables_find_target() did not care whether the found target was already
in use or not, so the same target instance was assigned to both rules
and therefore payload comparison happened over the same memory location.

With legacy iptables it is not possible to reuse a target: The only case
where two rules (i.e., iptables_command_state instances) could exist at
the same time is when comparing rules, but that's handled using libiptc.

The above change clashes with ebtables-nft's reuse of target objects:
While input parsing still just assigns the object from xtables_targets
list, rule conversion from nftnl to iptables_command_state allocates new
data. To fix this, make ebtables-nft input parsing use the common
command_jump() routine instead of its own simplified copy. In turn, this
also eliminates the ebtables-nft-specific variants of parse_target(),
though with a slight change of behaviour: Names of user-defined chains
are no longer allowed to contain up to 31 but merely 28 characters.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Florian Westphal <fw@strlen.de>

1 files changed, 10 insertions, 0 deletions

diff --git a/iptables/nft-bridge.c b/iptables/nft-bridge.c
index b4265c8a..7c390dfa 100644
--- a/iptables/nft-bridge.c
+++ b/iptables/nft-bridge.c
@@ -45,6 +45,16 @@ void ebt_cs_clean(struct iptables_command_state *cs)
 		free(m);
 		m = nm;
 	}
+
+	if (cs->target) {
+		free(cs->target->t);
+		cs->target->t = NULL;
+
+		if (cs->target == cs->target->next) {
+			free(cs->target);
+			cs->target = NULL;
+		}
+	}
 }
 
 static void ebt_print_mac(const unsigned char *mac)