[PATCH 11/11] [RFC] drm/i915/dp: fix array overflow warning

Arnd Bergmann arnd at kernel.org
Mon Mar 22 16:02:49 UTC 2021

From: Arnd Bergmann <arnd at arndb.de>

gcc-11 warns that intel_dp_check_mst_status() has a local array of
fourteen bytes and passes the last four bytes into a function that
expects a six-byte array:

drivers/gpu/drm/i915/display/intel_dp.c: In function ‘intel_dp_check_mst_status’:
drivers/gpu/drm/i915/display/intel_dp.c:4556:22: error: ‘drm_dp_channel_eq_ok’ reading 6 bytes from a region of size 4 [-Werror=stringop-overread]
 4556 |                     !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
      |                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/i915/display/intel_dp.c:4556:22: note: referencing argument 1 of type ‘const u8 *’ {aka ‘const unsigned char *’}
In file included from drivers/gpu/drm/i915/display/intel_dp.c:38:
include/drm/drm_dp_helper.h:1459:6: note: in a call to function ‘drm_dp_channel_eq_ok’
 1459 | bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
      |      ^~~~~~~~~~~~~~~~~~~~

Clearly something is wrong here, but I can't quite figure out what.
Changing the array size to 16 bytes avoids the warning, but is
probably the wrong solution here.

Signed-off-by: Arnd Bergmann <arnd at arndb.de>
 drivers/gpu/drm/i915/display/intel_dp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 8c12d5375607..830e2515f119 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -65,7 +65,7 @@
 #include "intel_vdsc.h"
 #include "intel_vrr.h"
-#define DP_DPRX_ESI_LEN 14
+#define DP_DPRX_ESI_LEN 16
 /* DP DSC throughput values used for slice count calculations KPixels/s */
 #define DP_DSC_PEAK_PIXEL_RATE			2720000

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