[PATCH 1/4] drm/i915/display: Fix out-of-bounds access in pipe-related tracepoints

Gustavo Sousa gustavo.sousa at intel.com
Thu Aug 29 22:00:44 UTC 2024 

Some display trace events use array members to store frame and scanline
counts for each pipe. However, those arrays are declared with 3 as the
hardcoded size, which cause out-of-bounds access when the trace event is
enabled on a platform that contains pipe D.

For example, when looking at the last 10 intel_pipe_enable events after
running IGT's testdisplay, we see the following on a MTL machine that
has pipe D available:

    $ trace-cmd report -R -F intel_pipe_enable \
    > | tail \
    > | sed 's,\(frame=.*\) \(scanline=.*\),\n\t   \1\n\t\2,'
         testdisplay-6715  [002] 17591.063491: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[83, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-6715  [003] 17591.264742: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[89, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-6715  [003] 17591.464541: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[8f, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-6715  [001] 17591.695827: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[95, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-6715  [000] 17591.915841: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[9a, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-6715  [000] 17592.127114: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[a0, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-6715  [002] 17592.358351: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[a8, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-6715  [002] 17592.580467: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[ae, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-6715  [000] 17592.950946: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[b8, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-6715  [004] 17593.079597: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[bf, 01, 00, 00, 01, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[00, 00, 00, 00, 3a, 04, 00, 00, 00, 00, 00, 00] pipe=1

Which shows zeros for pipe A's scanline counts. That happens because
pipe D's frame counts are overwriting them.

Let's fix that by making the arrays bring able to store info for all
possible pipes.

With the fix, we get the following:

    $ trace-cmd report -R -F intel_pipe_enable \
    > | tail \
    > | sed 's,\(frame=.*\) \(scanline=.*\),\n\t   \1\n\t\2,'
         testdisplay-7040  [003] 18067.489565: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[8c, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[8e, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-7040  [002] 18067.699312: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[92, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[58, 02, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-7040  [002] 18067.908868: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[98, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[58, 02, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-7040  [002] 18068.122802: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[9d, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[58, 02, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-7040  [003] 18068.331019: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[a2, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[e0, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-7040  [002] 18068.529067: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[a8, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[e0, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-7040  [003] 18068.742033: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[ae, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[e0, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-7040  [002] 18068.956229: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[b3, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[1f, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-7040  [002] 18069.295322: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[bb, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[7b, 08, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=0
         testdisplay-7040  [010] 18069.423527: intel_pipe_enable:     dev=0000:00:02.0
               frame=ARRAY[c2, 01, 00, 00, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00]
            scanline=ARRAY[d0, 05, 00, 00, 3a, 04, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00] pipe=1

Which makes more sense now.

Signed-off-by: Gustavo Sousa <gustavo.sousa at intel.com>
---
 drivers/gpu/drm/i915/display/intel_display_trace.h | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_trace.h b/drivers/gpu/drm/i915/display/intel_display_trace.h
index c734ef1fba3c..8a3185862089 100644
--- a/drivers/gpu/drm/i915/display/intel_display_trace.h
+++ b/drivers/gpu/drm/i915/display/intel_display_trace.h
@@ -15,6 +15,7 @@
 
 #include "i915_drv.h"
 #include "intel_crtc.h"
+#include "intel_display_limits.h"
 #include "intel_display_types.h"
 #include "intel_vblank.h"
 
@@ -27,8 +28,8 @@ TRACE_EVENT(intel_pipe_enable,
 
 	    TP_STRUCT__entry(
 			     __string(dev, __dev_name_kms(crtc))
-			     __array(u32, frame, 3)
-			     __array(u32, scanline, 3)
+			     __array(u32, frame, I915_MAX_PIPES)
+			     __array(u32, scanline, I915_MAX_PIPES)
 			     __field(enum pipe, pipe)
 			     ),
 	    TP_fast_assign(
@@ -55,8 +56,8 @@ TRACE_EVENT(intel_pipe_disable,
 
 	    TP_STRUCT__entry(
 			     __string(dev, __dev_name_kms(crtc))
-			     __array(u32, frame, 3)
-			     __array(u32, scanline, 3)
+			     __array(u32, frame, I915_MAX_PIPES)
+			     __array(u32, scanline, I915_MAX_PIPES)
 			     __field(enum pipe, pipe)
 			     ),
 
@@ -184,8 +185,8 @@ TRACE_EVENT(intel_memory_cxsr,
 
 	    TP_STRUCT__entry(
 			     __string(dev, __dev_name_i915(dev_priv))
-			     __array(u32, frame, 3)
-			     __array(u32, scanline, 3)
+			     __array(u32, frame, I915_MAX_PIPES)
+			     __array(u32, scanline, I915_MAX_PIPES)
 			     __field(bool, old)
 			     __field(bool, new)
 			     ),
-- 
2.46.0

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