CVE-2026-89771

/// Technical description

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

ring-buffer: Fix subbuf resize race with ring buffer readers

trace_buffer subbuf_size is read lockless in ring_buffer_read_page() and

ring_buffer_read_start(), while it can simultaneously be resized with

ring_buffer_subbuf_order_set().

Instead of trace_buffer::subbuf_size, use bpage::order in

ring_buffer_read_start() and ring_buffer_read_page().

In ring_buffer_read_start(), even with resize_disabled, there is still a

possibility of a race with a buffer modification. Hold the trace_buffer

mutex to synchronise with any pending ring buffer order modification.

trace_buffer::subbuf_size is now actually useless, remove it. Also,

create accessors rb_subbuf_capacity() and rb_page_capacity() which

return the actual size available for storing events, while

rb_subbuf_size() returns the actual subbuf page-size.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References