From: Ido Schimmel <idosch@idosch.org>
To: David Ahern <dsahern@kernel.org>
Cc: kuba@kernel.org, davem@davemloft.net, pabeni@redhat.com,
netdev@vger.kernel.org, Gwangun Jung <exsociety@gmail.com>
Subject: Re: [PATCH net] ipv4: Handle attempt to delete multipath route when fib_info contains an nh reference
Date: Wed, 5 Oct 2022 22:08:03 +0300 [thread overview]
Message-ID: <Yz3WE+cBd9YUj7Bp@shredder> (raw)
In-Reply-To: <20221005181257.8897-1-dsahern@kernel.org>
On Wed, Oct 05, 2022 at 12:12:57PM -0600, David Ahern wrote:
> 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.
Cool bug... Managed to reproduce with:
# ip nexthop add id 1 blackhole
# ip route add 192.0.2.0/24 nhid 1
# ip route del 192.0.2.0/24 nexthop via 198.51.100.1 nexthop via 198.51.100.2
Maybe add to tools/testing/selftests/net/fib_nexthops.sh ?
Checked IPv6 and I don't think we can hit it there, but I will double
check tomorrow morning.
>
> Fixes: 493ced1ac47c ("ipv4: Allow routes to use nexthop objects")
> Reported-by: Gwangun Jung <exsociety@gmail.com>
> Signed-off-by: David Ahern <dsahern@kernel.org>
> ---
> net/ipv4/fib_semantics.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
> index 2dc97583d279..17caa73f57e6 100644
> --- a/net/ipv4/fib_semantics.c
> +++ b/net/ipv4/fib_semantics.c
> @@ -926,6 +926,10 @@ int fib_nh_match(struct net *net, struct fib_config *cfg, struct fib_info *fi,
> if (!cfg->fc_mp)
> return 0;
>
> + /* multipath spec and nexthop id are mutually exclusive */
> + if (fi->nh)
> + return 1;
> +
> rtnh = cfg->fc_mp;
> remaining = cfg->fc_mp_len;
There is already such a check above for the non-multipath check, maybe
we can just move it up to cover both cases? Something like:
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,
next prev parent reply other threads:[~2022-10-05 19:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-05 18:12 [PATCH net] ipv4: Handle attempt to delete multipath route when fib_info contains an nh reference David Ahern
2022-10-05 19:08 ` Ido Schimmel [this message]
2022-10-05 19:27 ` David Ahern
2022-10-06 6:49 ` Ido Schimmel
2022-10-06 7:29 ` Paolo Abeni
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