CVE-2026-43042mpls: add seqcount to protect the platform_label{,s} pair

Official description

In the Linux kernel, the following vulnerability has been resolved: mpls: add seqcount to protect the platform_label{,s} pair The RCU-protected codepaths (mpls_forward, mpls_dump_routes) can have an inconsistent view of platform_labels vs platform_label in case of a concurrent resize (resize_platform_label_table, under platform_mutex). This can lead to OOB accesses. This patch adds a seqcount, so that we get a consistent snapshot. Note that mpls_label_ok is also susceptible to this, so the check against RTA_DST in rtm_to_route_config, done outside platform_mutex, is not sufficient. This value gets passed to mpls_label_ok once more in both mpls_route_add and mpls_route_del, so there is no issue, but that additional check must not be removed.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/6b9184ebc936f791631e51e783ab30320b3770e4
• https://git.kernel.org/stable/c/0d377825548fe598595b5a5fa4a309fb593d8fb4
• https://git.kernel.org/stable/c/8adc5b6fc876928d8c95555d30b66fa50b07421e
• https://git.kernel.org/stable/c/5bb3caf0bbfb56f1a00d2af072ac3d8395a3b9ef
• https://git.kernel.org/stable/c/629ec78ef8608d955ce217880cdc3e1873af3a15