[PATCH 6.0 111/124] ipv4: Handle attempt to delete multipath route when fib_info contains an nh reference

Greg Kroah-Hartman
2022-12-05T19:27:44Z

From: David Ahern <dsahern@kernel.org>

[ Upstream commit 61b91eb33a69c3be11b259c5ea484505cd79f883 ]

Gwangun Jung reported a slab-out-of-bounds access in fib_nh_match:
fib_nh_match+0xf98/0x1130 linux-6.0-rc7/net/ipv4/fib_semantics.c:961
fib_table_delete+0x5f3/0xa40 linux-6.0-rc7/net/ipv4/fib_trie.c:1753
inet_rtm_delroute+0x2b3/0x380 linux-6.0-rc7/net/ipv4/fib_frontend.c:874

Separate nexthop objects are mutually exclusive with the legacy
multipath spec. Fix fib_nh_match to return if the config for the
to be deleted route contains a multipath spec while the fib_info
is using a nexthop object.

Fixes: 493ced1ac47c ("ipv4: Allow routes to use nexthop objects")
Fixes: 6bf92d70e690 ("net: ipv4: fix route with nexthop object delete warning")
Reported-by: Gwangun Jung <exsociety@gmail.com>
Signed-off-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Tested-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: d5082d386eee ("ipv4: Fix route deletion when nexthop info is not specified")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/fib_semantics.c | 8 ++++----
tools/testing/selftests/net/fib_nexthops.sh | 5 +++++
2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 2dc97583d279..e9a7f70a54df 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -888,13 +888,13 @@ int fib_nh_match(struct net *net, struct fib_config *cfg, struct fib_info *fi,
return 1;
}

+ /* cannot match on nexthop object attributes */
+ if (fi->nh)
+ return 1;
+
if (cfg->fc_oif || cfg->fc_gw_family) {
struct fib_nh *nh;

- /* cannot match on nexthop object attributes */
- if (fi->nh)
- return 1;
-
nh = fib_info_nh(fi, 0);
if (cfg->fc_encap) {
if (fib_encap_match(net, cfg->fc_encap_type,
diff --git a/tools/testing/selftests/net/fib_nexthops.sh b/tools/testing/selftests/net/fib_nexthops.sh
index d5a0dd548989..ee5e98204d3d 100755
--- a/tools/testing/selftests/net/fib_nexthops.sh
+++ b/tools/testing/selftests/net/fib_nexthops.sh
@@ -1223,6 +1223,11 @@ ipv4_fcnal()
log_test $rc 0 "Delete nexthop route warning"
run_cmd "$IP route delete 172.16.101.1/32 nhid 12"
run_cmd "$IP nexthop del id 12"
+
+ run_cmd "$IP nexthop add id 21 via 172.16.1.6 dev veth1"
+ run_cmd "$IP ro add 172.16.101.0/24 nhid 21"
+ run_cmd "$IP ro del 172.16.101.0/24 nexthop via 172.16.1.7 dev veth1 nexthop via 172.16.1.8 dev veth1"
+ log_test $? 2 "Delete multipath route with only nh id based entry"
}

ipv4_grp_fcnal()
--
2.35.1