Patch "tcp: fix return value for partial writes" has been added to the 4.8-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    tcp: fix return value for partial writes

to the 4.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tcp-fix-return-value-for-partial-writes.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Fri Nov 18 11:35:46 CET 2016
From: Eric Dumazet <edumazet@google.com>
Date: Wed, 2 Nov 2016 14:41:50 -0700
Subject: tcp: fix return value for partial writes

From: Eric Dumazet <edumazet@google.com>


[ Upstream commit 79d8665b9545e128637c51cf7febde9c493b6481 ]

After my commit, tcp_sendmsg() might restart its loop after
processing socket backlog.

If sk_err is set, we blindly return an error, even though we
copied data to user space before.

We should instead return number of bytes that could be copied,
otherwise user space might resend data and corrupt the stream.

This might happen if another thread is using recvmsg(MSG_ERRQUEUE)
to process timestamps.

Issue was diagnosed by Soheil and Willem, big kudos to them !

Fixes: d41a69f1d390f ("tcp: make tcp_sendmsg() aware of socket backlog")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Tested-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/tcp.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1145,7 +1145,7 @@ restart:
 
 	err = -EPIPE;
 	if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
-		goto out_err;
+		goto do_error;
 
 	sg = !!(sk->sk_route_caps & NETIF_F_SG);
 


Patches currently in stable-queue which might be from edumazet@google.com are

queue-4.8/net-__skb_flow_dissect-must-cap-its-return-value.patch
queue-4.8/tcp-take-care-of-truncations-done-by-sk_filter.patch
queue-4.8/net-clear-sk_err_soft-in-sk_clone_lock.patch
queue-4.8/dccp-do-not-release-listeners-too-soon.patch
queue-4.8/net-mangle-zero-checksum-in-skb_checksum_help.patch
queue-4.8/tcp-fix-return-value-for-partial-writes.patch
queue-4.8/ipv6-dccp-fix-out-of-bound-access-in-dccp_v6_err.patch
queue-4.8/ipv6-dccp-add-missing-bind_conflict-to-dccp_ipv6_mapped.patch
queue-4.8/tcp-fix-potential-memory-corruption.patch
queue-4.8/dccp-do-not-send-reset-to-already-closed-sockets.patch
queue-4.8/dccp-fix-out-of-bound-access-in-dccp_v4_err.patch
queue-4.8/sock-fix-sendmmsg-for-partial-sendmsg.patch