From: Hangbin Liu <liuhangbin@gmail.com>
To: netdev@vger.kernel.org
Cc: Stefano Brivio <sbrivio@redhat.com>, wenxu <wenxu@ucloud.cn>,
Alexei Starovoitov <ast@fb.com>,
"David S . Miller" <davem@davemloft.net>,
Eric Dumazet <eric.dumazet@gmail.com>,
Hangbin Liu <liuhangbin@gmail.com>
Subject: [PATCH 2/2] xfrm/xfrm_policy: fix dst dev null pointer dereference in collect_md mode
Date: Mon, 19 Aug 2019 15:53:27 +0800 [thread overview]
Message-ID: <20190819075327.32412-3-liuhangbin@gmail.com> (raw)
In-Reply-To: <20190819075327.32412-1-liuhangbin@gmail.com>
In decode_session{4,6} there is a possibility that the skb dst dev is NULL,
e,g, with tunnel collect_md mode, which will cause kernel crash.
Here is what the code path looks like, for GRE:
- ip6gre_tunnel_xmit
- ip6gre_xmit_ipv6
- __gre6_xmit
- ip6_tnl_xmit
- if skb->len - t->tun_hlen - eth_hlen > mtu; return -EMSGSIZE
- icmpv6_send
- icmpv6_route_lookup
- xfrm_decode_session_reverse
- decode_session4
- oif = skb_dst(skb)->dev->ifindex; <-- here
- decode_session6
- oif = skb_dst(skb)->dev->ifindex; <-- here
The reason is __metadata_dst_init() init dst->dev to NULL by default.
We could not fix it in __metadata_dst_init() as there is no dev supplied.
On the other hand, the skb_dst(skb)->dev is actually not needed as we
called decode_session{4,6} via xfrm_decode_session_reverse(), so oif is not
used by: fl4->flowi4_oif = reverse ? skb->skb_iif : oif;
So make a dst dev check here should be clean and safe.
Fixes: 8d79266bc48c ("ip6_tunnel: add collect_md mode to IPv6 tunnels")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
net/xfrm/xfrm_policy.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 8ca637a72697..ec94f5795ea4 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -3269,7 +3269,7 @@ decode_session4(struct sk_buff *skb, struct flowi *fl, bool reverse)
struct flowi4 *fl4 = &fl->u.ip4;
int oif = 0;
- if (skb_dst(skb))
+ if (skb_dst(skb) && skb_dst(skb)->dev)
oif = skb_dst(skb)->dev->ifindex;
memset(fl4, 0, sizeof(struct flowi4));
@@ -3387,7 +3387,7 @@ decode_session6(struct sk_buff *skb, struct flowi *fl, bool reverse)
nexthdr = nh[nhoff];
- if (skb_dst(skb))
+ if (skb_dst(skb) && skb_dst(skb)->dev)
oif = skb_dst(skb)->dev->ifindex;
memset(fl6, 0, sizeof(struct flowi6));
--
2.19.2
next prev parent reply other threads:[~2019-08-19 7:53 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-15 6:09 [PATCH net] tunnel: fix dev null pointer dereference when send pkg larger than mtu in collect_md mode Hangbin Liu
2019-08-15 9:16 ` Eric Dumazet
2019-08-16 3:24 ` Hangbin Liu
2019-08-16 4:01 ` Hangbin Liu
2019-08-16 8:23 ` Eric Dumazet
2019-08-16 10:51 ` Hangbin Liu
2019-08-19 7:53 ` [PATCHv2 0/2] " Hangbin Liu
2019-08-19 7:53 ` [PATCH 1/2] ipv4/icmp: fix rt dst dev null pointer dereference Hangbin Liu
2019-08-21 16:11 ` Julian Anastasov
2019-08-19 7:53 ` Hangbin Liu [this message]
2019-08-20 19:20 ` [PATCHv2 0/2] fix dev null pointer dereference when send pkg larger than mtu in collect_md mode David Miller
2019-08-21 2:09 ` [PATCHv3 0/2] fix dev null pointer dereference when send packets " Hangbin Liu
2019-08-21 2:09 ` [PATCHv3 1/2] ipv4/icmp: fix rt dst dev null pointer dereference Hangbin Liu
2019-08-21 2:09 ` [PATCHv3 2/2] xfrm/xfrm_policy: fix dst dev null pointer dereference in collect_md mode Hangbin Liu
2019-08-22 14:19 ` [PATCHv4 0/2] fix dev null pointer dereference when send packets larger than mtu " Hangbin Liu
2019-08-22 14:19 ` [PATCHv4 net 1/2] ipv4/icmp: fix rt dst dev null pointer dereference Hangbin Liu
2019-08-22 18:46 ` Julian Anastasov
2019-08-23 22:32 ` Jonathan Lemon
2019-08-22 14:19 ` [PATCHv4 net 2/2] xfrm/xfrm_policy: fix dst dev null pointer dereference in collect_md mode Hangbin Liu
2019-08-23 22:30 ` Jonathan Lemon
2019-08-24 21:51 ` [PATCHv4 0/2] fix dev null pointer dereference when send packets larger than mtu " David Miller
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