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Subject[patch 37/48] tcp: Fix length tcp_splice_data_recv passes to skb_splice_bits.
2.6.28-stable review patch.  If anyone has any objections, please let us know.


From: Dimitris Michailidis <>

[ Upstream commit 9fa5fdf291c9b58b1cb8b4bb2a0ee57efa21d635 ]

tcp_splice_data_recv has two lengths to consider: the len parameter it
gets from tcp_read_sock, which specifies the amount of data in the skb,
and rd_desc->count, which is the amount of data the splice caller still
wants. Currently it passes just the latter to skb_splice_bits, which then
splices min(rd_desc->count, skb->len - offset) bytes.

Most of the time this is fine, except when the skb contains urgent data.
In that case len goes only up to the urgent byte and is less than
skb->len - offset. By ignoring len tcp_splice_data_recv may a) splice
data tcp_read_sock told it not to, b) return to tcp_read_sock a value > len.

Now, tcp_read_sock doesn't handle used > len and leaves the socket in a
bad state (both sk_receive_queue and copied_seq are bad at that point)
resulting in duplicated data and corruption.

Fix by passing min(rd_desc->count, len) to skb_splice_bits.

Signed-off-by: Dimitris Michailidis <>
Acked-by: Eric Dumazet <>
Signed-off-by: David S. Miller <>
Signed-off-by: Greg Kroah-Hartman <>

net/ipv4/tcp.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -522,7 +522,8 @@ static int tcp_splice_data_recv(read_des
struct tcp_splice_state *tss = rd_desc->;
int ret;

- ret = skb_splice_bits(skb, offset, tss->pipe, rd_desc->count, tss->flags);
+ ret = skb_splice_bits(skb, offset, tss->pipe, min(rd_desc->count, len),
+ tss->flags);
if (ret > 0)
rd_desc->count -= ret;
return ret;

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