path: root/net/ipv6/ip6_output.c
diff options
mode: <>2015-04-01 17:07:44 +0200
committerDavid S. Miller <>2015-04-06 16:12:49 -0400
commitf60e5990d9c1424af9dbca60a23ba2a1c7c1ce90 (patch)
treebba5ed057073e42c0113473e1cdbff0bc46ab875 /net/ipv6/ip6_output.c
parent576b7cd2f6ff1e90b3fc0a000d2fe74f8a50a4bb (diff)
ipv6: protect skb->sk accesses from recursive dereference inside the stack
We should not consult skb->sk for output decisions in xmit recursion levels > 0 in the stack. Otherwise local socket settings could influence the result of e.g. tunnel encapsulation process. ipv6 does not conform with this in three places: 1) ip6_fragment: we do consult ipv6_npinfo for frag_size 2) sk_mc_loop in ipv6 uses skb->sk and checks if we should loop the packet back to the local socket 3) ip6_skb_dst_mtu could query the settings from the user socket and force a wrong MTU Furthermore: In sk_mc_loop we could potentially land in WARN_ON(1) if we use a PF_PACKET socket ontop of an IPv6-backed vxlan device. Reuse xmit_recursion as we are currently only interested in protecting tunnel devices. Cc: Jiri Pirko <> Signed-off-by: Hannes Frederic Sowa <> Signed-off-by: David S. Miller <>
Diffstat (limited to 'net/ipv6/ip6_output.c')
1 files changed, 2 insertions, 1 deletions
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 7e80b61b51ff..36cf0ab685a0 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -542,7 +542,8 @@ int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
struct sk_buff *frag;
struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
- struct ipv6_pinfo *np = skb->sk ? inet6_sk(skb->sk) : NULL;
+ struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ?
+ inet6_sk(skb->sk) : NULL;
struct ipv6hdr *tmp_hdr;
struct frag_hdr *fh;
unsigned int mtu, hlen, left, len;