CVE-2026-89499

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.