From 7f7708f0055e49e331f267700aa8b2ee879f004c Mon Sep 17 00:00:00 2001 From: Michael Braun Date: Tue, 16 Mar 2010 00:26:22 -0700 Subject: bridge: Fix br_forward crash in promiscuous mode From: Michael Braun bridge: Fix br_forward crash in promiscuous mode It's a linux-next kernel from 2010-03-12 on an x86 system and it OOPs in the bridge module in br_pass_frame_up (called by br_handle_frame_finish) because brdev cannot be dereferenced (its set to a non-null value). Adding some BUG_ON statements revealed that BR_INPUT_SKB_CB(skb)->brdev == br-dev (as set in br_handle_frame_finish first) only holds until br_forward is called. The next call to br_pass_frame_up then fails. Digging deeper it seems that br_forward either frees the skb or passes it to NF_HOOK which will in turn take care of freeing the skb. The same is holds for br_pass_frame_ip. So it seems as if two independent skb allocations are required. As far as I can see, commit b33084be192ee1e347d98bb5c9e38a53d98d35e2 ("bridge: Avoid unnecessary clone on forward path") removed skb duplication and so likely causes this crash. This crash does not happen on 2.6.33. I've therefore modified br_forward the same way br_flood has been modified so that the skb is not freed if skb0 is going to be used and I can confirm that the attached patch resolves the issue for me. Signed-off-by: Herbert Xu Signed-off-by: David S. Miller --- net/bridge/br_input.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/bridge/br_input.c') diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c index 53b39851d87..08a72e63fb8 100644 --- a/net/bridge/br_input.c +++ b/net/bridge/br_input.c @@ -90,7 +90,7 @@ int br_handle_frame_finish(struct sk_buff *skb) if (skb) { if (dst) - br_forward(dst->dst, skb); + br_forward(dst->dst, skb, skb2); else br_flood_forward(br, skb, skb2); } -- cgit v1.2.3-18-g5258