From 91781004b9c029ee55b7aa9ef950a373ba865dc6 Mon Sep 17 00:00:00 2001
From: James Chapman <jchapman@katalix.com>
Date: Mon, 5 Nov 2007 23:32:37 -0800
Subject: [PATCH] [PPP]: L2TP: Fix oops in transmit and receive paths
Changes made on 18-sep to fix skb handling in the pppol2tp driver
broke the transmit and receive paths. Users are only running into this
now because distros are now using 2.6.23 and I must have messed up
when I tested the change.
For receive, we now do our own calculation of how much to pull from
the skb (variable length L2TP header) rather than using
skb_transport_offset(). Also, if the skb isn't a data packet, it must
be passed back to UDP with skb->data pointing to the UDP header.
For transmit, make sure skb->sk is set up because ip_queue_xmit()
needs it.
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
drivers/net/pppol2tp.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)
diff --git a/drivers/net/pppol2tp.c b/drivers/net/pppol2tp.c
index f8904fd92369..a7556cd2df79 100644
--- a/drivers/net/pppol2tp.c
+++ b/drivers/net/pppol2tp.c
@@ -488,7 +488,7 @@ static int pppol2tp_recv_core(struct sock *sock, struct sk_buff *skb)
{
struct pppol2tp_session *session = NULL;
struct pppol2tp_tunnel *tunnel;
- unsigned char *ptr;
+ unsigned char *ptr, *optr;
u16 hdrflags;
u16 tunnel_id, session_id;
int length;
@@ -496,7 +496,7 @@ static int pppol2tp_recv_core(struct sock *sock, struct sk_buff *skb)
tunnel = pppol2tp_sock_to_tunnel(sock);
if (tunnel == NULL)
- goto error;
+ goto no_tunnel;
/* UDP always verifies the packet length. */
__skb_pull(skb, sizeof(struct udphdr));
@@ -509,7 +509,7 @@ static int pppol2tp_recv_core(struct sock *sock, struct sk_buff *skb)
}
/* Point to L2TP header */
- ptr = skb->data;
+ optr = ptr = skb->data;
/* Get L2TP header flags */
hdrflags = ntohs(*(__be16*)ptr);
@@ -637,12 +637,14 @@ static int pppol2tp_recv_core(struct sock *sock, struct sk_buff *skb)
/* If offset bit set, skip it. */
if (hdrflags & L2TP_HDRFLAG_O) {
offset = ntohs(*(__be16 *)ptr);
- skb->transport_header += 2 + offset;
- if (!pskb_may_pull(skb, skb_transport_offset(skb) + 2))
- goto discard;
+ ptr += 2 + offset;
}
- __skb_pull(skb, skb_transport_offset(skb));
+ offset = ptr - optr;
+ if (!pskb_may_pull(skb, offset))
+ goto discard;
+
+ __skb_pull(skb, offset);
/* Skip PPP header, if present. In testing, Microsoft L2TP clients
* don't send the PPP header (PPP header compression enabled), but
@@ -652,6 +654,9 @@ static int pppol2tp_recv_core(struct sock *sock, struct sk_buff *skb)
* Note that skb->data[] isn't dereferenced from a u16 ptr here since
* the field may be unaligned.
*/
+ if (!pskb_may_pull(skb, 2))
+ goto discard;
+
if ((skb->data[0] == 0xff) && (skb->data[1] == 0x03))
skb_pull(skb, 2);
@@ -709,6 +714,10 @@ discard:
return 0;
error:
+ /* Put UDP header back */
+ __skb_push(skb, sizeof(struct udphdr));
+
+no_tunnel:
return 1;
}
@@ -1050,6 +1059,8 @@ static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
/* Get routing info from the tunnel socket */
dst_release(skb->dst);
skb->dst = sk_dst_get(sk_tun);
+ skb_orphan(skb);
+ skb->sk = sk_tun;
/* Queue the packet to IP for output */
len = skb->len;
--
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