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authorFlorian Westphal <fw@strlen.de>2016-03-12 11:14:42 +0100
committerDavid S. Miller <davem@davemloft.net>2016-03-14 15:46:41 -0400
commit8626c56c8279b88b91b8df55345cdf89542d5e90 (patch)
treef9a237a3a6fa51ab1a68d1f91584ad1eaf1071f7 /net/bridge
parent180a2c542ce904e256ba0d8732517d7f42b3f3fa (diff)
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bridge: fix potential use-after-free when hook returns QUEUE or STOLEN verdict
Zefir Kurtisi reported kernel panic with an openwrt specific patch. However, it turns out that mainline has a similar bug waiting to happen. Once NF_HOOK() returns the skb is in undefined state and must not be used. Moreover, the okfn must consume the skb to support async processing (NF_QUEUE). Current okfn in this spot doesn't consume it and caller assumes that NF_HOOK return value tells us if skb was freed or not, but thats wrong. It "works" because no in-tree user registers a NFPROTO_BRIDGE hook at LOCAL_IN that returns STOLEN or NF_QUEUE verdicts. Once we add NF_QUEUE support for nftables bridge this will break -- NF_QUEUE holds the skb for async processing, caller will erronoulsy return RX_HANDLER_PASS and on reinject netfilter will access free'd skb. Fix this by pushing skb up the stack in the okfn instead. NB: It also seems dubious to use LOCAL_IN while bypassing PRE_ROUTING completely in this case but this is how its been forever so it seems preferable to not change this. Cc: Felix Fietkau <nbd@openwrt.org> Cc: Zefir Kurtisi <zefir.kurtisi@neratec.com> Signed-off-by: Florian Westphal <fw@strlen.de> Tested-by: Zefir Kurtisi <zefir.kurtisi@neratec.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/bridge')
-rw-r--r--net/bridge/br_input.c16
1 files changed, 7 insertions, 9 deletions
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index f7fba74108a9..160797722228 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -222,7 +222,10 @@ static int br_handle_local_finish(struct net *net, struct sock *sk, struct sk_bu
/* check if vlan is allowed, to avoid spoofing */
if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid))
br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
- return 0; /* process further */
+
+ BR_INPUT_SKB_CB(skb)->brdev = p->br->dev;
+ br_pass_frame_up(skb);
+ return 0;
}
/*
@@ -284,14 +287,9 @@ rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
}
/* Deliver packet to local host only */
- if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN,
- dev_net(skb->dev), NULL, skb, skb->dev, NULL,
- br_handle_local_finish)) {
- return RX_HANDLER_CONSUMED; /* consumed by filter */
- } else {
- *pskb = skb;
- return RX_HANDLER_PASS; /* continue processing */
- }
+ NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, dev_net(skb->dev),
+ NULL, skb, skb->dev, NULL, br_handle_local_finish);
+ return RX_HANDLER_CONSUMED;
}
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