Commit a0d1b4af authored by Jacob Wen's avatar Jacob Wen Committed by Greg Kroah-Hartman

l2tp: copy 4 more bytes to linear part if necessary

[ Upstream commit 91c524708de6207f59dd3512518d8a1c7b434ee3 ]

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: fd558d18 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts")
Suggested-by: default avatarGuillaume Nault <>
Signed-off-by: default avatarJacob Wen <>
Acked-by: default avatarGuillaume Nault <>
Signed-off-by: default avatarDavid S. Miller <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent f9b9a8ea
......@@ -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_MAX 14
/* Default trace flags */
......@@ -860,7 +859,7 @@ 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);
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