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| author | Michael Braun <michael-dev@fami-braun.de> | 2010-03-16 08:26:22 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2010-03-16 08:26:22 +0100 |
| commit | 7f7708f0055e49e331f267700aa8b2ee879f004c (patch) | |
| tree | 385da7d1b722232c3c9003af52079318aa51326e /net/bridge/br_forward.c | |
| parent | bridge: Move NULL mdb check into br_mdb_ip_get (diff) | |
| download | linux-7f7708f0055e49e331f267700aa8b2ee879f004c.tar.xz linux-7f7708f0055e49e331f267700aa8b2ee879f004c.zip | |
bridge: Fix br_forward crash in promiscuous mode
From: Michael Braun <michael-dev@fami-braun.de>
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 <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/bridge/br_forward.c')
| -rw-r--r-- | net/bridge/br_forward.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c index d61e6f741125..8347916efe88 100644 --- a/net/bridge/br_forward.c +++ b/net/bridge/br_forward.c @@ -19,6 +19,10 @@ #include <linux/netfilter_bridge.h> #include "br_private.h" +static int deliver_clone(struct net_bridge_port *prev, struct sk_buff *skb, + void (*__packet_hook)(const struct net_bridge_port *p, + struct sk_buff *skb)); + /* Don't forward packets to originating port or forwarding diasabled */ static inline int should_deliver(const struct net_bridge_port *p, const struct sk_buff *skb) @@ -94,14 +98,18 @@ void br_deliver(const struct net_bridge_port *to, struct sk_buff *skb) } /* called with rcu_read_lock */ -void br_forward(const struct net_bridge_port *to, struct sk_buff *skb) +void br_forward(const struct net_bridge_port *to, struct sk_buff *skb, struct sk_buff *skb0) { if (should_deliver(to, skb)) { - __br_forward(to, skb); + if (skb0) + deliver_clone(to, skb, __br_forward); + else + __br_forward(to, skb); return; } - kfree_skb(skb); + if (!skb0) + kfree_skb(skb); } static int deliver_clone(struct net_bridge_port *prev, struct sk_buff *skb, |