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authorOctavian Purdila <opurdila@ixiacom.com>2008-06-04 15:45:58 -0700
committerDavid S. Miller <davem@davemloft.net>2008-06-04 15:45:58 -0700
commit293ad60401da621b8b329abbe8c388edb25f658a (patch)
treefb2fdaf7721c8efa36b0b47f7b63d4e600217dbb
parent26af65cbeb2467a486ae4fc7242c94e470c67c50 (diff)
tcp: Fix for race due to temporary drop of the socket lock in skb_splice_bits.
skb_splice_bits temporary drops the socket lock while iterating over the socket queue in order to break a reverse locking condition which happens with sendfile. This, however, opens a window of opportunity for tcp_collapse() to aggregate skbs and thus potentially free the current skb used in skb_splice_bits and tcp_read_sock. This patch fixes the problem by (re-)getting the same "logical skb" after the lock has been temporary dropped. Based on idea and initial patch from Evgeniy Polyakov. Signed-off-by: Octavian Purdila <opurdila@ixiacom.com> Acked-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/core/skbuff.c5
-rw-r--r--net/ipv4/tcp.c9
2 files changed, 11 insertions, 3 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 5c459f2b7985..1e556d312117 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1445,6 +1445,7 @@ done:
if (spd.nr_pages) {
int ret;
+ struct sock *sk = __skb->sk;
/*
* Drop the socket lock, otherwise we have reverse
@@ -1455,9 +1456,9 @@ done:
* we call into ->sendpage() with the i_mutex lock held
* and networking will grab the socket lock.
*/
- release_sock(__skb->sk);
+ release_sock(sk);
ret = splice_to_pipe(pipe, &spd);
- lock_sock(__skb->sk);
+ lock_sock(sk);
return ret;
}
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index f88653138621..ab66683b8043 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1227,7 +1227,14 @@ int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
copied += used;
offset += used;
}
- if (offset != skb->len)
+ /*
+ * If recv_actor drops the lock (e.g. TCP splice
+ * receive) the skb pointer might be invalid when
+ * getting here: tcp_collapse might have deleted it
+ * while aggregating skbs from the socket queue.
+ */
+ skb = tcp_recv_skb(sk, seq-1, &offset);
+ if (!skb || (offset+1 != skb->len))
break;
}
if (tcp_hdr(skb)->fin) {

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