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netfilter: bridge: replace physindev with physinif in nf_bridge_info

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[ Upstream commit 9874808878d9eed407e3977fd11fee49de1e1d86 ]

An skb can be added to a neigh->arp_queue while waiting for an arp
reply. Where original skb's skb->dev can be different to neigh's
neigh->dev. For instance in case of bridging dnated skb from one veth to
another, the skb would be added to a neigh->arp_queue of the bridge.

As skb->dev can be reset back to nf_bridge->physindev and used, and as
there is no explicit mechanism that prevents this physindev from been
freed under us (for instance neigh_flush_dev doesn't cleanup skbs from
different device's neigh queue) we can crash on e.g. this stack:

arp_process
  neigh_update
    skb = __skb_dequeue(&neigh->arp_queue)
      neigh_resolve_output(..., skb)
        ...
          br_nf_dev_xmit
            br_nf_pre_routing_finish_bridge_slow
              skb->dev = nf_bridge->physindev
              br_handle_frame_finish

Let's use plain ifindex instead of net_device link. To peek into the
original net_device we will use dev_get_by_index_rcu(). Thus either we
get device and are safe to use it or we don't get it and drop skb.

Fixes: c4e70a87d9 ("netfilter: bridge: rename br_netfilter.c to br_netfilter_hooks.c")
Suggested-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Pavel Tikhomirov
2024-01-11 23:06:40 +08:00
committed by Greg Kroah-Hartman
parent 754ca18ed3
commit 7ae19ee81c
6 changed files with 61 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/netfilter_bridge.h
View File

@@ -42,7 +42,7 @@ static inline int nf_bridge_get_physinif(const struct sk_buff *skb)
if (!nf_bridge)
return 0;
return nf_bridge->physindev ? nf_bridge->physindev->ifindex : 0;
return nf_bridge->physinif;
}
static inline int nf_bridge_get_physoutif(const struct sk_buff *skb)
@@ -60,7 +60,7 @@ nf_bridge_get_physindev(const struct sk_buff *skb, struct net *net)
{
const struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
return nf_bridge ? nf_bridge->physindev : NULL;
return nf_bridge ? dev_get_by_index_rcu(net, nf_bridge->physinif) : NULL;
}
static inline struct net_device *

2
include/linux/skbuff.h
View File

@@ -301,7 +301,7 @@ struct nf_bridge_info {
u8 bridged_dnat:1;
u8 sabotage_in_done:1;
__u16 frag_max_size;
struct net_device *physindev;
int physinif;
/* always valid & non-NULL from FORWARD on, for physdev match */
struct net_device *physoutdev;