CVE-2026-46100

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

fs: afs: revert mmap_prepare() change

Partially reverts commit 9d5403b1036c ("fs: convert most other
generic_file_*mmap() users to .mmap_prepare()").

This is because the .mmap invocation establishes a refcount, but
.mmap_prepare is called at a point where a merge or an allocation failure
might happen after the call, which would leak the refcount increment.

Functionality is being added to permit the use of .mmap_prepare in this
case, but in the interim, we need to fix this.