perf/core: Check kernel access when kernel callchains are requested

Overview

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

perf/core: Check kernel access when kernel callchains are requested

perf_event_open() currently gates perf_allow_kernel() only on !attr.exclude_kernel.

However, users can still request kernel callchain collection with attr.exclude_callchain_kernel == 0 even when attr.exclude_kernel == 1. That still requires kernel profiling privilege, but the existing check does not enforce it.

Update the permission check to call perf_allow_kernel() when either kernel sampling is requested or kernel callchains are requested.

This keeps permission checks aligned with requested data and prevents unprivileged use of kernel callchain capture.

Affected

• Linux >= 0764771dab80d7b84b9a271bee7f1b21a04a3f0c < 132bee76097be421ab3012130b5b506324cf2be1
• Linux >= 0764771dab80d7b84b9a271bee7f1b21a04a3f0c < 2581b43e162cfc43e6f5d8dd8d2b38f3441550de
• Linux >= 0764771dab80d7b84b9a271bee7f1b21a04a3f0c < 6e187281f978a2bff98ead6aa40f8ddc9a2c9afb
• Linux >= 0764771dab80d7b84b9a271bee7f1b21a04a3f0c < a4573a3838ae4fc73b70019cfa1dac9aaea7cc2f
• Linux 2.6.31

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.