In the Linux kernel, the following vulnerability has been resolved: ring-buffer: Make cpu_buffer::free_page a buffer_data_read_page Discar

In the Linux kernel, the following vulnerability has been resolved:

ring-buffer: Make cpu_buffer::free_page a buffer_data_read_page

Discarding a cached reader page after a concurrent ring buffer resize
uses the new global subbuf_order for the free_pages() call. This
mismatched order may crashes the kernel or leaks memory because the cached
page was allocated under the old size.

Save the actual free_page order alongside the page address to ensure we
always refer to the correct value and do not rely on the potentially
stalled cpu_buffer->subbuf_order value. The simplest is to make
free_page a buffer_data_read_page which already covers exactly what we
need: a page address and a page order.