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++;