Bug 2422697 (CVE-2025-68186)

Summary: CVE-2025-68186 kernel: Linux kernel: Denial of Service in ring-buffer component
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in the Linux kernel. An issue in the ring-buffer component, specifically within the `ring_buffer_map_get_reader()` function, can lead to an incorrect warning. This occurs when a reader catches up to a writer, causing the `rb_get_reader_page()` function to return NULL unexpectedly. A local user could exploit this to cause a Denial of Service (DoS).
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Description OSIDB Bzimport 2025-12-16 14:04:36 UTC 
In the Linux kernel, the following vulnerability has been resolved:

ring-buffer: Do not warn in ring_buffer_map_get_reader() when reader catches up

The function ring_buffer_map_get_reader() is a bit more strict than the
other get reader functions, and except for certain situations the
rb_get_reader_page() should not return NULL. If it does, it triggers a
warning.

This warning was triggering but after looking at why, it was because
another acceptable situation was happening and it wasn't checked for.

If the reader catches up to the writer and there's still data to be read
on the reader page, then the rb_get_reader_page() will return NULL as
there's no new page to get.

In this situation, the reader page should not be updated and no warning
should trigger.
Comment 1 Alexander B 2025-12-17 02:15:57 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025121633-CVE-2025-68186-8a42@gregkh/T