| From 1d9093457b243061a9bba23543c38726e864a643 Mon Sep 17 00:00:00 2001 |
| From: Tristan Hume <tristan@thume.ca> |
| Date: Thu, 27 Jan 2022 17:08:06 -0500 |
| Subject: perf/x86/intel/pt: Fix crash with stop filters in single-range mode |
| |
| From: Tristan Hume <tristan@thume.ca> |
| |
| commit 1d9093457b243061a9bba23543c38726e864a643 upstream. |
| |
| 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. |
| |
| Fixes: 670638477aed ("perf/x86/intel/pt: Opportunistically use single range output mode") |
| Signed-off-by: Tristan Hume <tristan@thume.ca> |
| Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> |
| Reviewed-by: Adrian Hunter <adrian.hunter@intel.com> |
| Cc: stable@kernel.org |
| Link: https://lkml.kernel.org/r/20220127220806.73664-1-tristan@thume.ca |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| arch/x86/events/intel/pt.c | 5 +++-- |
| 1 file changed, 3 insertions(+), 2 deletions(-) |
| |
| --- a/arch/x86/events/intel/pt.c |
| +++ b/arch/x86/events/intel/pt.c |
| @@ -897,8 +897,9 @@ static void pt_handle_status(struct pt * |
| * means we are already losing data; need to let the decoder |
| * know. |
| */ |
| - if (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries) || |
| - buf->output_off == pt_buffer_region_size(buf)) { |
| + if (!buf->single && |
| + (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries) || |
| + buf->output_off == pt_buffer_region_size(buf))) { |
| perf_aux_output_flag(&pt->handle, |
| PERF_AUX_FLAG_TRUNCATED); |
| advance++; |