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CVE-2024-47678: icmp: change the order of rate limits

5.5 CVSS

Description

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.

CVSS Base Severity: MEDIUM

CVSS Base Score: 5.5

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Vendor: Linux

Product: Linux

EPSS Score: 0.03% (probability of being exploited)

EPSS Percentile: 5.59% (scored less or equal to compared to others)

EPSS Date: 2025-06-02 (when was this score calculated)

SSVC Exploitation: none

SSVC Technical Impact: partial

SSVC Automatable: false