Bug 2401491 (CVE-2023-53549)

Summary: CVE-2023-53549 kernel: netfilter: ipset: Rework long task execution when adding/deleting entries
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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An uncontrolled resource consumption flaw was found in the Linux kernel's netfilter ipset subsystem when processing large batch operations. A local user with CAP_NET_ADMIN capability can trigger this issue by adding or deleting a large number of ipset entries in a single operation, causing the kernel to execute long-running tasks without yielding. This results in soft lockup conditions and denial of service through system unresponsiveness.
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Description OSIDB Bzimport 2025-10-04 16:03:38 UTC
In the Linux kernel, the following vulnerability has been resolved:

netfilter: ipset: Rework long task execution when adding/deleting entries

When adding/deleting large number of elements in one step in ipset, it can
take a reasonable amount of time and can result in soft lockup errors. The
patch 5f7b51bf09ba ("netfilter: ipset: Limit the maximal range of
consecutive elements to add/delete") tried to fix it by limiting the max
elements to process at all. However it was not enough, it is still possible
that we get hung tasks. Lowering the limit is not reasonable, so the
approach in this patch is as follows: rely on the method used at resizing
sets and save the state when we reach a smaller internal batch limit,
unlock/lock and proceed from the saved state. Thus we can avoid long
continuous tasks and at the same time removed the limit to add/delete large
number of elements in one step.

The nfnl mutex is held during the whole operation which prevents one to
issue other ipset commands in parallel.