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ipv4: Handle attempt to delete multipath route when fib_info contains…
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… an nh reference

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: 493ced1 ("ipv4: Allow routes to use nexthop objects")
Fixes: 6bf92d7 ("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>
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David Ahern authored and David S. Miller committed Oct 7, 2022
1 parent 3030cbf commit 61b91eb
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Showing 2 changed files with 9 additions and 4 deletions.
8 changes: 4 additions & 4 deletions net/ipv4/fib_semantics.c
Original file line number Diff line number Diff line change
Expand Up @@ -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,
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5 changes: 5 additions & 0 deletions tools/testing/selftests/net/fib_nexthops.sh
Original file line number Diff line number Diff line change
Expand Up @@ -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()
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