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| author | Florian Westphal <fw@strlen.de> | 2016-03-12 11:14:42 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-03-14 15:46:41 -0400 |
| commit | 8626c56c8279b88b91b8df55345cdf89542d5e90 (patch) | |
| tree | f9a237a3a6fa51ab1a68d1f91584ad1eaf1071f7 /net/bridge/br_input.c | |
| parent | 180a2c542ce904e256ba0d8732517d7f42b3f3fa (diff) | |
| download | linux-8626c56c8279b88b91b8df55345cdf89542d5e90.tar.gz | |
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/br_input.c')
| -rw-r--r-- | net/bridge/br_input.c | 16 |
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; } forward: |