CVE-2024-39503

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

netfilter: ipset: Fix race between namespace cleanup and gc in the list:set type

Lion Ackermann reported that there is a race condition between namespace cleanup in ipset and the garbage collection of the list:set type. The namespace cleanup can destroy the list:set type of sets while the gc of the set type is waiting to run in rcu cleanup. The latter uses data from the destroyed set which thus leads use after free. The patch contains the following parts:

• When destroying all sets, first remove the garbage collectors, then wait if needed and then destroy the sets.
• Fix the badly ordered wait then remove gc for the destroy a single set case.
• Fix the missing rcu locking in the list:set type in the userspace test case.
• Use proper RCU list handlings in the list:set type.

The patch depends on c1193d9bbbd3 (netfilter: ipset: Add list flush to cancel_gc).

Weakness

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Software

Extended Description

A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:

A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.

Potential Mitigations

• Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
• Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/29.html

References

• https://git.kernel.org/stable/c/0f1bb77c6d837c9513943bc7c08f04c5cc5c6568
• https://git.kernel.org/stable/c/2ba35b37f780c6410bb4bba9c3072596d8576702
• https://git.kernel.org/stable/c/390b353d1a1da3e9c6c0fd14fe650d69063c95d6
• https://git.kernel.org/stable/c/4e7aaa6b82d63e8ddcbfb56b4fd3d014ca586f10
• https://git.kernel.org/stable/c/90ae20d47de602198eb69e6cd7a3db3420abfc08
• https://git.kernel.org/stable/c/93b53c202b51a69e42ca57f5a183f7e008e19f83
• https://git.kernel.org/stable/c/c0761d1f1ce1d5b85b5e82bbb714df12de1aa8c3
• https://git.kernel.org/stable/c/0f1bb77c6d837c9513943bc7c08f04c5cc5c6568
• https://git.kernel.org/stable/c/2ba35b37f780c6410bb4bba9c3072596d8576702
• https://git.kernel.org/stable/c/390b353d1a1da3e9c6c0fd14fe650d69063c95d6
• https://git.kernel.org/stable/c/4e7aaa6b82d63e8ddcbfb56b4fd3d014ca586f10
• https://git.kernel.org/stable/c/90ae20d47de602198eb69e6cd7a3db3420abfc08
• https://git.kernel.org/stable/c/93b53c202b51a69e42ca57f5a183f7e008e19f83
• https://git.kernel.org/stable/c/c0761d1f1ce1d5b85b5e82bbb714df12de1aa8c3
• https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html