Subject: [PATCH 18/18] net/unix: fix logic about sk_peek_offset

From: Andrey Vagin <[email-masked]>
Date: Fri, 2 Oct 2015 00:05:36 +0300

[ Upstream commit e9193d60d363e4dff75ff6d43a48f22be26d59c7 ]

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" <[email-masked]> (maintainer:NETWORKING
Cc: Eric Dumazet <[email-masked]> (commit_signer:1/14=7%)
Cc: Aaron Conole <[email-masked]>
Fixes: 9f389e35674f ("af_unix: return data from multiple SKBs on recv() with MSG_PEEK flag")
Signed-off-by: Andrey Vagin <[email-masked]>
Tested-by: Aaron Conole <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 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 5650154..76e6669 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1938,6 +1938,11 @@ static int unix_stream_recvmsg(struct socket *sock, struct msghdr *msg,
 		goto out;
 	}
 
+	if (flags & MSG_PEEK)
+		skip = sk_peek_offset(sk, flags);
+	else
+		skip = 0;
+
 	do {
 		int chunk;
 		struct sk_buff *skb, *last;
@@ -1984,7 +1989,6 @@ again:
 			break;
 		}
 
-		skip = sk_peek_offset(sk, flags);
 		while (skip >= unix_skb_len(skb)) {
 			skip -= unix_skb_len(skb);
 			last = skb;
@@ -2046,14 +2050,12 @@ again:
 			if (UNIXCB(skb).fp)
 				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);
-- 
1.7.10.4