netfilter buglog - Apr 2023 - [Bug 1676] New: nft check config causes segmentation fault when using variables for devices in the chain

https://bugzilla.netfilter.org/show_bug.cgi?id=1676

            Bug ID: 1676
           Summary: nft check config causes segmentation fault when using
                    variables for devices in the chain
           Product: nftables
           Version: 1.0.x
          Hardware: x86_64
                OS: Debian GNU/Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: nft
          Assignee: pablo at netfilter.org
          Reporter: jinesh at onelittlehope.com

Setup details:

  libnftables1:amd64           1.0.6-2
  libnftnl11:amd64             1.2.4-2
  nftables                     1.0.6-2

  Linux debianvm 6.1.0-7-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.20-2
(2023-04-08) x86_64 GNU/Linux

Reproduction steps:

1. Create a test.conf file containing:

---snip---
#!/usr/sbin/nft -f

define lan_interfaces = {eth0}
flush ruleset
table netdev filter {
  chain ingress {
    type filter hook ingress devices = $lan_interfaces priority -500; policy
accept;
  }
}
---snip---

2. Run nft -c -f test.conf

Expect no output as syntax is valid. Instead get a Segmentation fault.

Notes:

- I think the issue is that the lan_interfaces variable cannot have a single
element. It needs to have more than one element. e.g. define lan_interfaces
{eth0,lo} works fine and no seg fault.

- I also found that define lan_interfaces = {{eth0}} doesn't generate a seg
fault.

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https://bugzilla.netfilter.org/show_bug.cgi?id=1676

Pablo Neira Ayuso <pablo at netfilter.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #1 from Pablo Neira Ayuso <pablo at netfilter.org> ---
Patch:

https://patchwork.ozlabs.org/project/netfilter-devel/patch/20230425145407.2802-1-pablo
at netfilter.org/

Thanks for reporting.

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https://bugzilla.netfilter.org/show_bug.cgi?id=1676

--- Comment #2 from Pablo Neira Ayuso <pablo at netfilter.org> ---
89b60bc18ca7 ("mnl: handle singleton element in netdevice set")

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