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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 /net/ipv4
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>
Diffstat (limited to 'net/ipv4')
-rw-r--r--net/ipv4/tcp.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index f8865313862..ab66683b804 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) {