net: Fix oops from tcp_collapse() when using splice()

[ Upstream commit baff42ab1494528907bf4d5870359e31711746ae ]

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@digidescorp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 564a0f87cd66ef083310e0145ea621f77c4ce157..03c55acc29dfbd894460004b95e2583ff4f46529 100644 (file)
--- 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;