ipv6: fib6_select_path can not use out path for nexthop objects
Brian reported a crash in IPv6 code when using rpfilter with a setup
running FRR and external nexthop objects. The root cause of the crash
is fib6_select_path setting fib6_nh in the result to NULL because of
an improper check for nexthop objects.
More specifically, rpfilter invokes ip6_route_lookup with flowi6_oif
set causing fib6_select_path to be called with have_oif_match set.
fib6_select_path has early check on have_oif_match and jumps to the
out label which presumes a builtin fib6_nh. This path is invalid for
nexthop objects; for external nexthops fib6_select_path needs to just
return if the fib6_nh has already been set in the result otherwise it
returns after the call to nexthop_path_fib6_result. Update the check
on have_oif_match to not bail on external nexthops.
Update selftests for this problem.
Fixes: f88d8ea67fbd ("ipv6: Plumb support for nexthop object in a fib6_info")
Reported-by: Brian Rak <brak@choopa.com>
Signed-off-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 82cbb46..ea0be7c 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -431,9 +431,12 @@ void fib6_select_path(const struct net *net, struct fib6_result *res,
struct fib6_info *sibling, *next_sibling;
struct fib6_info *match = res->f6i;
- if ((!match->fib6_nsiblings && !match->nh) || have_oif_match)
+ if (!match->nh && (!match->fib6_nsiblings || have_oif_match))
goto out;
+ if (match->nh && have_oif_match && res->nh)
+ return;
+
/* We might have already computed the hash for ICMPv6 errors. In such
* case it will always be non-zero. Otherwise now is the time to do it.
*/