[3.13.y-ckt stable] Patch "tcp: Fix crash in TCP Fast Open" has been added to staging queue
Kamal Mostafa
kamal at canonical.com
Fri May 1 17:27:41 UTC 2015
This is a note to let you know that I have just added a patch titled
tcp: Fix crash in TCP Fast Open
to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree
which can be found at:
http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue
This patch is scheduled to be released in version 3.13.y-ckt20.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Kamal
------
>From 7d157c2eb5b4172a387e13f5a7864c295ac547f7 Mon Sep 17 00:00:00 2001
From: Ben Hutchings <ben at decadent.org.uk>
Date: Wed, 15 Apr 2015 19:00:32 +0100
Subject: 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 <ben at decadent.org.uk>
Acked-by: Eric Dumazet <edumazet at google.com>
[ kamal: pre-3.18-stable only; no upstream commit ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
net/ipv4/tcp_output.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index b692b0b..918f2db 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2907,6 +2907,7 @@ 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);
--
1.9.1
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