netdev - [PATCH net] l2tp: copy 4 more bytes to linear part if necessary

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20190131071856.22120-1-jian.w.wen@oracle.com>
Date:   Thu, 31 Jan 2019 15:18:56 +0800
From:   Jacob Wen <jian.w.wen@...cle.com>
To:     netdev@...r.kernel.org
Cc:     gnault@...hat.com
Subject: [PATCH net] l2tp: copy 4 more bytes to linear part if necessary

The size of L2TPv2 header with all optional fields is 14 bytes.
l2tp_udp_recv_core only moves 10 bytes to the linear part of a
skb. This may lead to l2tp_recv_common read data outside of a skb.

This patch make sure that there is at least 14 bytes in the linear
part of a skb to meet the maximum need of l2tp_udp_recv_core and
l2tp_recv_common. The minimum size of both PPP HDLC-like frame and
Ethernet frame is larger than 14 bytes, so we are safe to do so.

Also remove L2TP_HDR_SIZE_NOSEQ, it is unused now.

Fixes: fd558d186df2 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts")
Suggested-by: Guillaume Nault <gnault@...hat.com>
Signed-off-by: Jacob Wen <jian.w.wen@...cle.com>
---
 net/l2tp/l2tp_core.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index dd5ba0c11ab3..fed6becc5daf 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -83,8 +83,7 @@
 #define L2TP_SLFLAG_S	   0x40000000
 #define L2TP_SL_SEQ_MASK   0x00ffffff
 
-#define L2TP_HDR_SIZE_SEQ		10
-#define L2TP_HDR_SIZE_NOSEQ		6
+#define L2TP_HDR_SIZE_MAX		14
 
 /* Default trace flags */
 #define L2TP_DEFAULT_DEBUG_FLAGS	0
@@ -808,7 +807,7 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb)
 	__skb_pull(skb, sizeof(struct udphdr));
 
 	/* Short packet? */
-	if (!pskb_may_pull(skb, L2TP_HDR_SIZE_SEQ)) {
+	if (!pskb_may_pull(skb, L2TP_HDR_SIZE_MAX)) {
 		l2tp_info(tunnel, L2TP_MSG_DATA,
 			  "%s: recv short packet (len=%d)\n",
 			  tunnel->name, skb->len);
-- 
2.17.1