STABLE REQUEST: perf/core: Avoid put_page() when GUP fails

The patch titled ("perf/core: Avoid put_page() when GUP fails") has been merged into linus/master as commit 4716023a8f6a0f4a28047f14dd7ebdc319606b84.

The patch fixes an issue present in all v4.14+ kernels that can cause page reference count underflow, which can lead to unintentional page sharing.

The patch did not have cc: stable footer, so I'm manually requesting -stable inclusion into v4.14+.

There are some trivial conflicts in older kernels. I'd be happy to review/test, if that's useful.