On Tue, Mar 3, 2020 at 5:39 AM Kees Cook keescook@chromium.org wrote:

On Wed, Feb 19, 2020 at 10:22:29PM -0800, Kees Cook wrote:

...

Variables declared in a switch statement before any case statements cannot be automatically initialized with compiler instrumentation (as they are not part of any execution flow). With GCC's proposed automatic stack variable initialization feature, this triggers a warning (and they don't get initialized). Clang's automatic stack variable initialization (via CONFIG_INIT_STACK_ALL=y) doesn't throw a warning, but it also doesn't initialize such variables[1]. Note that these warnings (or silent skipping) happen before the dead-store elimination optimization phase, so even when the automatic initializations are later elided in favor of direct initializations, the warnings remain.

To avoid these problems, move such variables into the "case" where they're used or lift them up into the main function body.

drivers/gpu/drm/drm_edid.c: In function ‘drm_edid_to_eld’: drivers/gpu/drm/drm_edid.c:4395:9: warning: statement will never be executed [-Wswitch-unreachable] 4395 | int sad_count; | ^~~~~~~~~

[1] https://bugs.llvm.org/show_bug.cgi?id=44916

Signed-off-by: Kees Cook keescook@chromium.org

Ping. Can someone pick this up, please?

Whatever the reasons, but your original patch didn't make it through to dri-devel. Can you pls resubmit?

Thanks, Daniel

Thanks!

-Kees

...

---

drivers/gpu/drm/drm_edid.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index 805fb004c8eb..2941b65b427f 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -4392,9 +4392,9 @@ static void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid) dbl = cea_db_payload_len(db);

                  switch (cea_db_tag(db)) {

•                         int sad_count;
  

•                 case AUDIO_BLOCK: {
  
  

•                 case AUDIO_BLOCK:
  

•                         int sad_count;
                          /* Audio Data Block, contains SADs */
                          sad_count = min(dbl / 3, 15 - total_sad_count);
                          if (sad_count >= 1)
  

@@ -4402,6 +4402,7 @@ static void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid) &db[1], sad_count * 3); total_sad_count += sad_count; break;

•                 }
                  case SPEAKER_BLOCK:
                          /* Speaker Allocation Data Block */
                          if (dbl >= 1)
  
  

-- Kees Cook