From 293ad60401da621b8b329abbe8c388edb25f658a Mon Sep 17 00:00:00 2001 From: Octavian Purdila Date: Wed, 4 Jun 2008 15:45:58 -0700 Subject: 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 Acked-by: Evgeniy Polyakov Signed-off-by: David S. Miller --- net/ipv4/tcp.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'net/ipv4/tcp.c') 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) { -- cgit v1.2.3