From: Arnd Bergmann arnd@arndb.de
gcc warns about an out-of-bounds access when the using nonzero values for 'plane_id' on kmb->plane_status:
drivers/gpu/drm/kmb/kmb_plane.c: In function 'kmb_plane_atomic_disable': drivers/gpu/drm/kmb/kmb_plane.c:128:20: warning: array subscript 3 is above array bounds of 'struct layer_status[1]' [-Warray-bounds] 128 | kmb->plane_status[plane_id].ctrl = LCD_CTRL_GL2_ENABLE; | ~~~~~~~~~~~~~~~~~^~~~~~~~~~ drivers/gpu/drm/kmb/kmb_plane.c:125:20: warning: array subscript 2 is above array bounds of 'struct layer_status[1]' [-Warray-bounds] 125 | kmb->plane_status[plane_id].ctrl = LCD_CTRL_GL1_ENABLE; | ~~~~~~~~~~~~~~~~~^~~~~~~~~~ drivers/gpu/drm/kmb/kmb_plane.c:122:20: warning: array subscript 1 is above array bounds of 'struct layer_status[1]' [-Warray-bounds] 122 | kmb->plane_status[plane_id].ctrl = LCD_CTRL_VL2_ENABLE;
Having the array truncated to one entry seems intentional, so add a range check before indexing it to make it clearer what is going on and shut up the warning.
I received the warning from the kernel test robot after a private patch that turns on Warray-bounds unconditionally.
Fixes: 7f7b96a8a0a1 ("drm/kmb: Add support for KeemBay Display") Reported-by: kernel test robot lkp@intel.com Signed-off-by: Arnd Bergmann arnd@arndb.de --- drivers/gpu/drm/kmb/kmb_plane.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/gpu/drm/kmb/kmb_plane.c b/drivers/gpu/drm/kmb/kmb_plane.c index 8448d1edb553..be8eea3830c1 100644 --- a/drivers/gpu/drm/kmb/kmb_plane.c +++ b/drivers/gpu/drm/kmb/kmb_plane.c @@ -114,6 +114,9 @@ static void kmb_plane_atomic_disable(struct drm_plane *plane,
kmb = to_kmb(plane->dev);
+ if (WARN_ON(plane_id >= KMB_MAX_PLANES)) + return; + switch (plane_id) { case LAYER_0: kmb->plane_status[plane_id].ctrl = LCD_CTRL_VL1_ENABLE;