The Linux kernel ring-buffer vulnerability (CVE-2026-89499) arises when the remote swap_reader_page callback returns -EBUSY if the writer moves the head before the remote reader catches up, especially during event storms on small buffers. The affected function __rb_get_reader_page_from_remote() used to warn about this failure but proceeded with the unchanged reader ID and rearranged the local page list as if the swap succeeded. This could lead to splicing the same page as both previous and new reader and flooding logs under contention. The patch changes the handling to treat the callback failure as a recoverable error by logging a rate-limited warning and returning NULL, which callers already handle as a failed attempt, thus preventing the incorrect page splicing and log flooding.

This vulnerability could cause improper internal state in the ring-buffer subsystem, potentially leading to incorrect page splicing and excessive log flooding under high contention. There is no indication of direct security impact such as privilege escalation or denial of service beyond internal kernel logging and state consistency issues. No known exploits in the wild have been reported.

A fix has been implemented in the Linux kernel to handle the remote swap_reader_page callback failure correctly by treating it as a recoverable error and preventing improper page splicing and log flooding. Users should apply the official kernel updates that include this fix. Since no patch links or vendor advisories are provided, check the Linux kernel official repositories or security advisories for the relevant update.