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authorHerbert Xu <herbert@gondor.apana.org.au>2005-05-18 22:52:33 -0700
committerDavid S. Miller <davem@davemloft.net>2005-05-18 22:52:33 -0700
commit2fdba6b085eb7068e9594cfa55ffe40466184b4d (patch)
tree2f7325f9f62cc643caf6d6c8dd7a24b1cb94ebd0
parentd48102007d068df7ba3055cdc1723e12db1ba30f (diff)
downloadlinux-sh-2fdba6b085eb7068e9594cfa55ffe40466184b4d.tar.gz
[IPV4/IPV6] Ensure all frag_list members have NULL sk
Having frag_list members which holds wmem of an sk leads to nightmares with partially cloned frag skb's. The reason is that once you unleash a skb with a frag_list that has individual sk ownerships into the stack you can never undo those ownerships safely as they may have been cloned by things like netfilter. Since we have to undo them in order to make skb_linearize happy this approach leads to a dead-end. So let's go the other way and make this an invariant: For any skb on a frag_list, skb->sk must be NULL. That is, the socket ownership always belongs to the head skb. It turns out that the implementation is actually pretty simple. The above invariant is actually violated in the following patch for a short duration inside ip_fragment. This is OK because the offending frag_list member is either destroyed at the end of the slow path without being sent anywhere, or it is detached from the frag_list before being sent. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv4/ip_output.c8
-rw-r--r--net/ipv6/ip6_output.c14
2 files changed, 16 insertions, 6 deletions
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index daebd93fd8a0..760dc8238d65 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -490,6 +490,14 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
/* Partially cloned skb? */
if (skb_shared(frag))
goto slow_path;
+
+ BUG_ON(frag->sk);
+ if (skb->sk) {
+ sock_hold(skb->sk);
+ frag->sk = skb->sk;
+ frag->destructor = sock_wfree;
+ skb->truesize -= frag->truesize;
+ }
}
/* Everything is OK. Generate! */
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 0f0711417c9d..b78a53586804 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -552,13 +552,17 @@ static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
skb_headroom(frag) < hlen)
goto slow_path;
- /* Correct socket ownership. */
- if (frag->sk == NULL)
- goto slow_path;
-
/* Partially cloned skb? */
if (skb_shared(frag))
goto slow_path;
+
+ BUG_ON(frag->sk);
+ if (skb->sk) {
+ sock_hold(skb->sk);
+ frag->sk = skb->sk;
+ frag->destructor = sock_wfree;
+ skb->truesize -= frag->truesize;
+ }
}
err = 0;
@@ -1116,12 +1120,10 @@ int ip6_push_pending_frames(struct sock *sk)
tail_skb = &(tmp_skb->next);
skb->len += tmp_skb->len;
skb->data_len += tmp_skb->len;
-#if 0 /* Logically correct, but useless work, ip_fragment() will have to undo */
skb->truesize += tmp_skb->truesize;
__sock_put(tmp_skb->sk);
tmp_skb->destructor = NULL;
tmp_skb->sk = NULL;
-#endif
}
ipv6_addr_copy(final_dst, &fl->fl6_dst);