[patch 05/37] bridge-netfilter: dont overwrite memory outside of skb
From: Greg KH <gregkh@suse.de>
Date: 2006-09-06 23:01:20
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-stable review patch. If anyone has any objections, please let us know. ------------------ From: Stephen Hemminger <redacted> 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 <redacted> 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; --