CVE-2023-52501

In the Linux kernel, the following vulnerability has been resolved:
ring-buffer: Do not attempt to read past “commit” When iterating over the
ring buffer while the ring buffer is active, the writer can corrupt the
reader. There’s barriers to help detect this and handle it, but that code
missed the case where the last event was at the very end of the page and
has only 4 bytes left. The checks to detect the corruption by the writer to
reads needs to see the length of the event. If the length in the first 4
bytes is zero then the length is stored in the second 4 bytes. But if the
writer is in the process of updating that code, there’s a small window
where the length in the first 4 bytes could be zero even though the length
is only 4 bytes. That will cause rb_event_length() to read the next 4 bytes
which could happen to be off the allocated page. To protect against this,
fail immediately if the next event pointer is less than 8 bytes from the
end of the commit (last byte of data), as all events must be a minimum of 8
bytes anyway.