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Commit 75270f81 authored by David Ahern's avatar David Ahern Committed by Greg Kroah-Hartman
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ipv6: fib6_select_path can not use out path for nexthop objects 



[ Upstream commit 34fe5a1cf95c3f114068fc16d919c9cf4b00e428 ]

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: f88d8ea6 ("ipv6: Plumb support for nexthop object in a fib6_info")
Reported-by: default avatarBrian Rak <brak@choopa.com>
Signed-off-by: default avatarDavid Ahern <dsahern@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 1418b60e

net/ipv6/route.c

+4 −1
Original line number Diff line number Diff line
@@ -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.

	 */

tools/testing/selftests/net/fib_nexthops.sh

+13 −0
Original line number Diff line number Diff line
@@ -512,6 +512,19 @@ ipv6_fcnal_runtime() 
	run_cmd "$IP nexthop add id 86 via 2001:db8:91::2 dev veth1"

	run_cmd "$IP ro add 2001:db8:101::1/128 nhid 81"



	# rpfilter and default route

	$IP nexthop flush >/dev/null 2>&1

	run_cmd "ip netns exec me ip6tables -t mangle -I PREROUTING 1 -m rpfilter --invert -j DROP"

	run_cmd "$IP nexthop add id 91 via 2001:db8:91::2 dev veth1"

	run_cmd "$IP nexthop add id 92 via 2001:db8:92::2 dev veth3"

	run_cmd "$IP nexthop add id 93 group 91/92"

	run_cmd "$IP -6 ro add default nhid 91"

	run_cmd "ip netns exec me ping -c1 -w1 2001:db8:101::1"

	log_test $? 0 "Nexthop with default route and rpfilter"

	run_cmd "$IP -6 ro replace default nhid 93"

	run_cmd "ip netns exec me ping -c1 -w1 2001:db8:101::1"

	log_test $? 0 "Nexthop with multipath default route and rpfilter"



	# TO-DO:

	# existing route with old nexthop; append route with new nexthop

	# existing route with old nexthop; replace route with new