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| author | Hangbin Liu <liuhangbin@gmail.com> | 2019-08-22 22:19:49 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-09-06 10:23:33 +0200 |
| commit | 2905d7847cd59c4e4aba72a1b6f249f62156efb8 (patch) | |
| tree | ed77f16bb71aa9b798b8bb47b66be028b44e0ca3 /net | |
| parent | 1c7fbbc0fc3fe00812bc642b4378a700a1837bd9 (diff) | |
| download | linux-stable-2905d7847cd59c4e4aba72a1b6f249f62156efb8.tar.gz linux-stable-2905d7847cd59c4e4aba72a1b6f249f62156efb8.tar.bz2 linux-stable-2905d7847cd59c4e4aba72a1b6f249f62156efb8.zip | |
xfrm/xfrm_policy: fix dst dev null pointer dereference in collect_md mode
[ Upstream commit c3b4c3a47e05d5fecf7354d75824a9d1b37f3e84 ]
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.
v4: No changes.
v3: No changes.
v2: fix the issue in decode_session{4,6} instead of updating shared dst dev
in {ip_md, ip6}_tunnel_xmit.
Fixes: 8d79266bc48c ("ip6_tunnel: add collect_md mode to IPv6 tunnels")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Tested-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net')
| -rw-r--r-- | net/xfrm/xfrm_policy.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index 82be7780bbe8..d5342687fdca 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -3272,7 +3272,7 @@ 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)); @@ -3390,7 +3390,7 @@ 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)); |