CVE-2024-35839 netfilter: bridge: replace physindev with physinif in nf_bridge_info

2024-05-1714:27:30

Linux

www.cve.org

netfilter

bridge

linux kernel

vulnerability

skb

neigh

arp reply

6.4 Medium

AI Score

Confidence

Low

0.0004 Low

EPSS

Percentile

15.5%

JSON

In the Linux kernel, the following vulnerability has been resolved:

netfilter: bridge: replace physindev with physinif in nf_bridge_info

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.

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "include/linux/netfilter_bridge.h",
      "include/linux/skbuff.h",
      "net/bridge/br_netfilter_hooks.c",
      "net/bridge/br_netfilter_ipv6.c",
      "net/ipv4/netfilter/nf_reject_ipv4.c",
      "net/ipv6/netfilter/nf_reject_ipv6.c"
    ],
    "versions": [
      {
        "version": "c4e70a87d975",
        "lessThan": "7ae19ee81ca5",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "c4e70a87d975",
        "lessThan": "9325e3188a9c",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "c4e70a87d975",
        "lessThan": "544add1f1cfb",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "c4e70a87d975",
        "lessThan": "9874808878d9",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "include/linux/netfilter_bridge.h",
      "include/linux/skbuff.h",
      "net/bridge/br_netfilter_hooks.c",
      "net/bridge/br_netfilter_ipv6.c",
      "net/ipv4/netfilter/nf_reject_ipv4.c",
      "net/ipv6/netfilter/nf_reject_ipv6.c"
    ],
    "versions": [
      {
        "version": "4.2",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "4.2",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.1.75",
        "lessThanOrEqual": "6.1.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.6.14",
        "lessThanOrEqual": "6.6.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.7.2",
        "lessThanOrEqual": "6.7.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.8",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]