From: Ben Hutchings Date: Wed, 15 Apr 2015 18:00:32 +0000 (+0100) Subject: tcp: Fix crash in TCP Fast Open X-Git-Tag: v3.16.35~2335 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=53411a80e3449952336582f8689c458b63f85455;p=thirdparty%2Fkernel%2Fstable.git tcp: Fix crash in TCP Fast Open Commit 355a901e6cf1 ("tcp: make connect() mem charging friendly") changed tcp_send_syn_data() to perform an open-coded copy of the 'syn' skb rather than using skb_copy_expand(). The open-coded copy does not cover the skb_shared_info::gso_segs field, so in the new skb it is left set to 0. When this commit was backported into stable branches between 3.10.y and 3.16.7-ckty inclusive, it triggered the BUG() in tcp_transmit_skb(). Since Linux 3.18 the GSO segment count is kept in the tcp_skb_cb::tcp_gso_segs field and tcp_send_syn_data() does copy the tcp_skb_cb structure to the new skb, so mainline and newer stable branches are not affected. Set skb_shared_info::gso_segs to the correct value of 1. Signed-off-by: Ben Hutchings Acked-by: Eric Dumazet Signed-off-by: Luis Henriques --- diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index d5457e40f5beb..1ea0a07ab0b51 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2992,6 +2992,7 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn) goto fallback; syn_data->ip_summed = CHECKSUM_PARTIAL; memcpy(syn_data->cb, syn->cb, sizeof(syn->cb)); + skb_shinfo(syn_data)->gso_segs = 1; if (unlikely(memcpy_fromiovecend(skb_put(syn_data, space), fo->data->msg_iov, 0, space))) { kfree_skb(syn_data);