[PATCH 172/173] net: Fix oops from tcp_collapse() when using splice()

[Willy Tarreau]

2.6.27.59-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Steven J. Magnani <steve@xxxxxxxxxxxxxxx>

commit baff42ab1494528907bf4d5870359e31711746ae upstream.

tcp_read_sock() can have a eat skbs without immediately advancing copied_seq.
This can cause a panic in tcp_collapse() if it is called as a result
of the recv_actor dropping the socket lock.

A userspace program that splices data from a socket to either another
socket or to a file can trigger this bug.

Signed-off-by: Steven J. Magnani <steve@xxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 6afb6d8..2c75f89 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1368,6 +1368,7 @@ int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
 		sk_eat_skb(sk, skb, 0);
 		if (!desc->count)
 			break;
+		tp->copied_seq = seq;
 	}
 	tp->copied_seq = seq;
 


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