CVE-2025-38564

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

perf/core: Handle buffer mapping fail correctly in perf_mmap()

After successful allocation of a buffer or a successful attachment to an existing buffer perfmmap() tries to map the buffer read only into the page table. If that fails, the already set up page table entries are zapped, but the other perf specific side effects of that failure are not handled. The calling code just cleans up the VMA and does not invoke perfmmap_close().

This leaks reference counts, corrupts user->vm accounting and also results in an unbalanced invocation of event::event_mapped().

Cure this by moving the event::eventmapped() invocation before the maprange() call so that on maprange() failure perfmmapclose() can be invoked without causing an unbalanced event::eventunmapped() call.

perfmmapclose() undoes the reference counts and eventually frees buffers.