[patch 07/16] Fix L2TP oopses.

Greg KH
2007-11-15T06:44:48Z

[-- Attachment #1: fix-l2tp-oopses.patch --]
[-- Type: text/plain, Size: 3195 bytes --]

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

------------------
From: James Chapman <jchapman@katalix.com>

changeset 91781004b9c029ee55b7aa9ef950a373ba865dc6 in mainline.

[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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/net/pppol2tp.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)

--- a/drivers/net/pppol2tp.c
+++ b/drivers/net/pppol2tp.c
@@ -487,7 +487,7 @@ static int pppol2tp_recv_core(struct soc
{
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;
@@ -495,7 +495,7 @@ static int pppol2tp_recv_core(struct soc

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));
@@ -508,7 +508,7 @@ static int pppol2tp_recv_core(struct soc
}

/* Point to L2TP header */
- ptr = skb->data;
+ optr = ptr = skb->data;

/* Get L2TP header flags */
hdrflags = ntohs(*(__be16*)ptr);
@@ -636,12 +636,14 @@ static int pppol2tp_recv_core(struct soc
/* 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
@@ -651,6 +653,9 @@ static int pppol2tp_recv_core(struct soc
* 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);

@@ -708,6 +713,10 @@ discard:
return 0;

error:
+ /* Put UDP header back */
+ __skb_push(skb, sizeof(struct udphdr));
+
+no_tunnel:
return 1;
}

@@ -1049,6 +1058,8 @@ static int pppol2tp_xmit(struct ppp_chan
/* 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;

--