Reconfiguring MPLS channel while down causes segfault on bird 3.2.0

[David Petera]

Hi Max,

thanks for the bug report.

I've been able to reproduce it in our labs also, so can confirm it is 
indeed a bug in v3.

I have forwarded it to our issue tracker and our dev team will 
investigate it further.

If we need more information from you, we will let you know.

Happy routing,
David

PS: Thanks for the pointers!

David Petera (he/him) | BIRD Tech Support | CZ.NIC, z.s.p.o.

On 4/3/26 02:38, Max Hearnden via Bird-users wrote:
> Hello, I've found an issue with bird 3.2.0 which can be reproduced 
> with the following configuration (no peer required). Just run 
> configure after starting bird.
>
>
> router id 1;
>
> mpls table mtab;
> mpls domain mdom;
>
> protocol bgp test {
>   local 192.0.2.2 port 8179 as 65000;
>   neighbor 192.0.2.1 as 65001;
>   mpls {label policy aggregate;};
> }
>
> It appears that this issue is caused because c->mpls_map is only set 
> in mpls_channel_start instead of mpls_channel_init which would also 
> match the deallocation in mpls_channel_cleanup. This means that before 
> the channel is first up c->mpls_map is null and would cause a null 
> pointer dereference as part of mpls_fec_map_reconfigure (called in 
> mpls_channel_reconfigure).
>