linux-kernel - [PATCH 3.12 75/86] ipv6: check raw payload size correctly in ioctl

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Message-Id: <3fe5f786c2e7dcf61dc5373543aac0e6550f932c.1493888632.git.jslaby@suse.cz>
Date:   Thu,  4 May 2017 11:04:40 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Jamie Bainbridge <jbainbri@...hat.com>,
        "David S . Miller" <davem@...emloft.net>
Subject: [PATCH 3.12 75/86] ipv6: check raw payload size correctly in ioctl

From: Jamie Bainbridge <jbainbri@...hat.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

[ Upstream commit 105f5528b9bbaa08b526d3405a5bcd2ff0c953c8 ]

In situations where an skb is paged, the transport header pointer and
tail pointer can be the same because the skb contents are in frags.

This results in ioctl(SIOCINQ/FIONREAD) incorrectly returning a
length of 0 when the length to receive is actually greater than zero.

skb->len is already correctly set in ip6_input_finish() with
pskb_pull(), so use skb->len as it always returns the correct result
for both linear and paged data.

Signed-off-by: Jamie Bainbridge <jbainbri@...hat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
---
 net/ipv6/raw.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index c2afb29dc1d7..581662201ba9 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -1145,8 +1145,7 @@ static int rawv6_ioctl(struct sock *sk, int cmd, unsigned long arg)
 		spin_lock_bh(&sk->sk_receive_queue.lock);
 		skb = skb_peek(&sk->sk_receive_queue);
 		if (skb != NULL)
-			amount = skb_tail_pointer(skb) -
-				skb_transport_header(skb);
+			amount = skb->len;
 		spin_unlock_bh(&sk->sk_receive_queue.lock);
 		return put_user(amount, (int __user *)arg);
 	}
-- 
2.12.2