[3.16.y-ckt stable] Patch "net/unix: fix logic about sk_peek_offset" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    net/unix: fix logic about sk_peek_offset

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt19.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 16229f16750545db9bfe2ea5a48d1c7bf738475d Mon Sep 17 00:00:00 2001
From: Andrey Vagin <avagin at openvz.org>
Date: Fri, 2 Oct 2015 00:05:36 +0300
Subject: net/unix: fix logic about sk_peek_offset

commit e9193d60d363e4dff75ff6d43a48f22be26d59c7 upstream.

Now send with MSG_PEEK can return data from multiple SKBs.

Unfortunately we take into account the peek offset for each skb,
that is wrong. We need to apply the peek offset only once.

In addition, the peek offset should be used only if MSG_PEEK is set.

Cc: "David S. Miller" <davem at davemloft.net> (maintainer:NETWORKING
Cc: Eric Dumazet <edumazet at google.com> (commit_signer:1/14=7%)
Cc: Aaron Conole <aconole at bytheb.org>
Fixes: 9f389e35674f ("af_unix: return data from multiple SKBs on recv() with MSG_PEEK flag")
Signed-off-by: Andrey Vagin <avagin at openvz.org>
Tested-by: Aaron Conole <aconole at bytheb.org>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/unix/af_unix.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 30a705ee0ac8..2ae4a5915aa7 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1962,6 +1962,11 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
 		goto out;
 	}

+	if (flags & MSG_PEEK)
+		skip = sk_peek_offset(sk, flags);
+	else
+		skip = 0;
+
 	do {
 		int chunk;
 		struct sk_buff *skb, *last;
@@ -2008,7 +2013,6 @@ again:
 			break;
 		}

-		skip = sk_peek_offset(sk, flags);
 		while (skip >= unix_skb_len(skb)) {
 			skip -= unix_skb_len(skb);
 			last = skb;
@@ -2070,14 +2074,12 @@ again:
 			if (UNIXCB(skb).fp)
 				siocb->scm->fp = scm_fp_dup(UNIXCB(skb).fp);

-			if (skip) {
-				sk_peek_offset_fwd(sk, chunk);
-				skip -= chunk;
-			}
+			sk_peek_offset_fwd(sk, chunk);

 			if (UNIXCB(skb).fp)
 				break;

+			skip = 0;
 			last = skb;
 			unix_state_lock(sk);
 			skb = skb_peek_next(skb, &sk->sk_receive_queue);