perf/x86/intel/pt: Fix crash with stop filters in single-range mode

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: perf/x86/intel/pt: Fix crash with stop filters in single-range mode Add a check for !buf->single before calling pt_buffer_region_size in a place where a missing check can cause a kernel crash. Fixes a bug introduced by commit 670638477aed ("perf/x86/intel/pt: Opportunistically use single range output mode"), which added a support for PT single-range output mode. Since that commit if a PT stop filter range is hit while tracing, the kernel will crash because of a null pointer dereference in pt_handle_status due to calling pt_buffer_region_size without a ToPA configured. The commit which introduced single-range mode guarded almost all uses of the ToPA buffer variables with checks of the buf->single variable, but missed the case where tracing was stopped by the PT hardware, which happens when execution hits a configured stop filter. Tested that hitting a stop filter while PT recording successfully records a trace with this patch but crashes without this patch.

References

• https://git.kernel.org/stable/c/456f041e035913fcedb275aff6f8a71dfebcd394
• https://git.kernel.org/stable/c/e83d941fd3445f660d2f43647c580a320cc384f6
• https://git.kernel.org/stable/c/feffb6ae2c80b9a8206450cdef90f5943baced99
• https://git.kernel.org/stable/c/1d9093457b243061a9bba23543c38726e864a643