CVE-2026-68175: tracing: Fix resource leak on mmiotrace trace_pipe close

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

tracing: Fix resource leak on mmiotrace tracepipe close

The mmiotrace tracer was added May 12th 2008. At that time, resources created in pipeopen() could not be freed because there was not pipeclose function pointer of the tracer. The pipeclose function pointer was added in December 7th, 2009, but the mmiotrace tracer was not updated.

mmiopipeopen() allocates a headeriter and takes a pcidev reference when tracepipe is opened. mmioclose() frees them, but it was only wired to the tracer's .close callback.

tracingreleasepipe() invokes .pipeclose, not .close, when the tracepipe file is released. As a result, closing tracepipe with the mmiotrace tracer active leaked the headeriter allocation and left a stale pcidev reference.

Set .pipeclose to mmioclose, matching how functiongraph wires both callbacks to the same handler.

Note, if the tracepipe is read to completion, it will clean up the resources, but if one were to run:

# head -n 1 /sys/kernel/tracing/tracepipe VERSION 20070824

Over and over again, it would trigger a massive leak.