linux-kernel - [PATCH 4.7 04/41] udp: use sk_filter_trim_cap for udp{,6}_queue_rcv

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Date:	Sun, 14 Aug 2016 22:38:30 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>,
	Willem de Bruijn <willemb@...gle.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.7 04/41] udp: use sk_filter_trim_cap for udp{,6}_queue_rcv_skb

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

------------------

From: Daniel Borkmann <daniel@...earbox.net>

[ Upstream commit ba66bbe5480a012108958a71cff88b23dce84956 ]

After a612769774a3 ("udp: prevent bugcheck if filter truncates packet
too much"), there followed various other fixes for similar cases such
as f4979fcea7fd ("rose: limit sk_filter trim to payload").

Latter introduced a new helper sk_filter_trim_cap(), where we can pass
the trim limit directly to the socket filter handling. Make use of it
here as well with sizeof(struct udphdr) as lower cap limit and drop the
extra skb->len test in UDP's input path.

Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Cc: Willem de Bruijn <willemb@...gle.com>
Acked-by: Willem de Bruijn <willemb@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/udp.c |    4 +---
 net/ipv6/udp.c |    4 +---
 2 files changed, 2 insertions(+), 6 deletions(-)

--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1581,9 +1581,7 @@ int udp_queue_rcv_skb(struct sock *sk, s
 	    udp_lib_checksum_complete(skb))
 			goto csum_error;
 
-	if (sk_filter(sk, skb))
-		goto drop;
-	if (unlikely(skb->len < sizeof(struct udphdr)))
+	if (sk_filter_trim_cap(sk, skb, sizeof(struct udphdr)))
 		goto drop;
 
 	udp_csum_pull_header(skb);
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -618,9 +618,7 @@ int udpv6_queue_rcv_skb(struct sock *sk,
 	    udp_lib_checksum_complete(skb))
 		goto csum_error;
 
-	if (sk_filter(sk, skb))
-		goto drop;
-	if (unlikely(skb->len < sizeof(struct udphdr)))
+	if (sk_filter_trim_cap(sk, skb, sizeof(struct udphdr)))
 		goto drop;
 
 	udp_csum_pull_header(skb);