CVE-2026-89499ring-buffer: Stop remote reader update when page swap fails

Official description

In the Linux kernel, the following vulnerability has been resolved: ring-buffer: Stop remote reader update when page swap fails The remote swap_reader_page callback can return -EBUSY when the writer moves the head before the remote catches it, particularly during an event storm on a small buffer. __rb_get_reader_page_from_remote() currently warns about that failure but continues with the unchanged reader ID and rearranges the local page list as though the swap succeeded. Handle the callback failure as a recoverable error. Report it with pr_warn_ratelimited() and return NULL. Callers already handle a NULL reader page as a failed attempt. This avoids splicing the same page as both the previous and new reader without flooding the log under contention.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/a14a97048e48471e283d76879b83d2ae323e0722
• https://git.kernel.org/stable/c/5eab74874d11160725c42ab676ba97a797a362eb