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

icmp: change the order of rate limits

ICMP messages are ratelimited :

After the blamed commits, the two rate limiters are applied in this order:

1. host wide ratelimit (icmp_global_allow())

2. Per destination ratelimit (inetpeer based)

In order to avoid side-channels attacks, we need to apply
the per destination check first.

This patch makes the following change :

1. icmp_global_allow() checks if the host wide limit is reached.
   But credits are not yet consumed. This is deferred to 3)

2. The per destination limit is checked/updated.
   This might add a new node in inetpeer tree.

3. icmp_global_consume() consumes tokens if prior operations succeeded.

This means that host wide ratelimit is still effective
in keeping inetpeer tree small even under DDOS.

As a bonus, I removed icmp_global.lock as the fast path
can use a lock-free operation.

References

• https://nvd.nist.gov/vuln/detail/CVE-2024-47678
• https://git.kernel.org/stable/c/483397b4ba280813e4a9c161a0a85172ddb43d19
• https://git.kernel.org/stable/c/662ec52260cc07b9ae53ecd3925183c29d34288b
• https://git.kernel.org/stable/c/8c2bd38b95f75f3d2a08c93e35303e26d480d24e
• https://git.kernel.org/stable/c/997ba8889611891f91e8ad83583466aeab6239a3
• https://git.kernel.org/stable/c/a7722921adb046e3836eb84372241f32584bdb07