[patch 05/37] bridge-netfilter: dont overwrite memory outside of skb

Greg KH
2006-09-06T23:01:20Z

[-- Attachment #1: bridge-netfilter-don-t-overwrite-memory-outside-of-skb.patch --]
[-- Type: text/plain, Size: 1987 bytes --]

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

------------------
From: Stephen Hemminger <shemminger@osdl.org>

The bridge netfilter code needs to check for space at the
front of the skb before overwriting; otherwise if skb from
device doesn't have headroom, then it will cause random
memory corruption.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
include/linux/netfilter_bridge.h | 16 ++++++++++++----
net/bridge/br_forward.c | 10 +++++++---
2 files changed, 19 insertions(+), 7 deletions(-)

--- linux-2.6.17.11.orig/include/linux/netfilter_bridge.h
+++ linux-2.6.17.11/include/linux/netfilter_bridge.h
@@ -47,18 +47,26 @@ enum nf_br_hook_priorities {
#define BRNF_BRIDGED 0x08
#define BRNF_NF_BRIDGE_PREROUTING 0x10

-
/* Only used in br_forward.c */
-static inline
-void nf_bridge_maybe_copy_header(struct sk_buff *skb)
+static inline int nf_bridge_maybe_copy_header(struct sk_buff *skb)
{
+ int err;
+
if (skb->nf_bridge) {
if (skb->protocol == __constant_htons(ETH_P_8021Q)) {
+ err = skb_cow(skb, 18);
+ if (err)
+ return err;
memcpy(skb->data - 18, skb->nf_bridge->data, 18);
skb_push(skb, 4);
- } else
+ } else {
+ err = skb_cow(skb, 16);
+ if (err)
+ return err;
memcpy(skb->data - 16, skb->nf_bridge->data, 16);
+ }
}
+ return 0;
}

/* This is called by the IP fragmenting code and it ensures there is
--- linux-2.6.17.11.orig/net/bridge/br_forward.c
+++ linux-2.6.17.11/net/bridge/br_forward.c
@@ -43,11 +43,15 @@ int br_dev_queue_push_xmit(struct sk_buf
else {
#ifdef CONFIG_BRIDGE_NETFILTER
/* ip_refrag calls ip_fragment, doesn't copy the MAC header. */
- nf_bridge_maybe_copy_header(skb);
+ if (nf_bridge_maybe_copy_header(skb))
+ kfree_skb(skb);
+ else
#endif
- skb_push(skb, ETH_HLEN);
+ {
+ skb_push(skb, ETH_HLEN);

- dev_queue_xmit(skb);
+ dev_queue_xmit(skb);
+ }
}

return 0;

--