netdev - [PATCH] ipv6: check raw payload size correctly in ioctl

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Message-Id: <1493167407-27969-1-git-send-email-jbainbri@redhat.com>
Date:   Wed, 26 Apr 2017 10:43:27 +1000
From:   Jamie Bainbridge <jbainbri@...hat.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org
Cc:     Jamie Bainbridge <jbainbri@...hat.com>
Subject: [PATCH] ipv6: check raw payload size correctly in ioctl

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>
---
 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 f174e76e6505d4045e940c9fceef765d2aaa937d..0da6a12b5472e322d679572c7244e5c9bc467741 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -1178,8 +1178,7 @@ 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)
-			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);
 	}
-- 
1.8.3.1