Vulnerability CVE-2023-52501
Published: 2024-03-02

Description:
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.

 References:
https://git.kernel.org/stable/c/cee5151c5410e868826b8afecfb356f3799ebea3
https://git.kernel.org/stable/c/344f2f3e61a90f0150c754796ec9a17fcaeec03d
https://git.kernel.org/stable/c/b08a4938229dbb530a35c41b83002a1457c6ff49
https://git.kernel.org/stable/c/75fc9e99b3a71006720ad1e029db11a4b5c32d4a
https://git.kernel.org/stable/c/95a404bd60af6c4d9d8db01ad14fe8957ece31ca
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