Bug 1224726 (CVE-2024-35839)

Summary: VUL-0: CVE-2024-35839: kernel: netfilter: bridge: replace physindev with physinif in nf_bridge_info
Product: [Novell Products] SUSE Security Incidents Reporter: SMASH SMASH <smash_bz>
Component: IncidentsAssignee: Denis Kirjanov <denis.kirjanov>
Status: NEW --- QA Contact: Security Team bot <security-team>
Severity: Normal    
Priority: P3 - Medium CC: gabriele.sonnu, jlee, mhocko
Version: unspecified   
Target Milestone: ---   
Hardware: Other   
OS: Other   
URL: https://smash.suse.de/issue/406402/
Whiteboard: CVSSv3.1:SUSE:CVE-2024-35839:5.5:(AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
Found By: Security Response Team Services Priority:
Business Priority: Blocker: ---
Marketing QA Status: --- IT Deployment: ---

Description SMASH SMASH 2024-05-20 16:09:29 UTC
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.

References:
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2024-35839
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2024/CVE-2024-35839.mbox
https://git.kernel.org/stable/c/7ae19ee81ca56b13c50a78de6c47d5b8fdc9d97b
https://git.kernel.org/stable/c/9325e3188a9cf3f69fc6f32af59844bbc5b90547
https://git.kernel.org/stable/c/544add1f1cfb78c3dfa3e6edcf4668f6be5e730c
https://git.kernel.org/stable/c/9874808878d9eed407e3977fd11fee49de1e1d86
https://www.cve.org/CVERecord?id=CVE-2024-35839
https://bugzilla.redhat.com/show_bug.cgi?id=2281284
Comment 1 Joey Lee 2024-05-21 06:58:36 UTC
https://www.suse.com/security/cve/CVE-2024-35839.html
cvss 5.5
Comment 3 Joey Lee 2024-05-23 11:20:02 UTC
Hi Denis,

Because this is a issue for netfilter. Could you please help to handle it?

If this is not in your area, just reset bug assigner to kernel-bugs@suse.de. Kernel Security Sentinel will find other expert.

Thanks a lot!