drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
From: Arnd Bergmann <arnd@arndb.de>
clang-21 points out a variable that is conditionally initialized
but then dereferenced:
drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c:1138:6: error: variable 'crtc_state' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
1138 | if (plane_state->crtc)
| ^~~~~~~~~~~~~~~~~
drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c:1142:58: note: uninitialized use occurs here
1142 | ret = dpu_plane_atomic_check_nosspp(plane, plane_state, crtc_state);
| ^~~~~~~~~~
drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c:1138:2: note: remove the 'if' if its condition is always true
1138 | if (plane_state->crtc)
| ^~~~~~~~~~~~~~~~~~~~~~
1139 | crtc_state = drm_atomic_get_new_crtc_state(state,
drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c:1132:35: note: initialize the variable 'crtc_state' to silence this warning
1132 | struct drm_crtc_state *crtc_state;
| ^
| = NULL
The bug is real, but the suggestion from clang to set it to NULL is
unfortunately just as harmful as dereferencing a NULL pointer is little
better than uninitialized data.
Change the function to return an error in this case.
Fixes: 774bcfb73176 ("drm/msm/dpu: add support for virtual planes")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
index 01171c535a27..4987f2f2fee0 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
@@ -1135,10 +1135,10 @@ static int dpu_plane_virtual_atomic_check(struct drm_plane *plane,
if (IS_ERR(plane_state))
return PTR_ERR(plane_state);
- if (plane_state->crtc)
- crtc_state = drm_atomic_get_new_crtc_state(state,
- plane_state->crtc);
+ if (!plane_state->crtc)
+ return -ENXIO;
+ crtc_state = drm_atomic_get_new_crtc_state(state, plane_state->crtc);
ret = dpu_plane_atomic_check_nosspp(plane, plane_state, crtc_state);
if (ret)
return ret;
--
2.39.5On Thu, Aug 07, 2025 at 09:19:48AM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> clang-21 points out a variable that is conditionally initialized
> but then dereferenced:
>
> drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c:1138:6: error: variable 'crtc_state' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
> 1138 | if (plane_state->crtc)
> | ^~~~~~~~~~~~~~~~~
> drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c:1142:58: note: uninitialized use occurs here
> 1142 | ret = dpu_plane_atomic_check_nosspp(plane, plane_state, crtc_state);
> | ^~~~~~~~~~
> drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c:1138:2: note: remove the 'if' if its condition is always true
> 1138 | if (plane_state->crtc)
> | ^~~~~~~~~~~~~~~~~~~~~~
> 1139 | crtc_state = drm_atomic_get_new_crtc_state(state,
> drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c:1132:35: note: initialize the variable 'crtc_state' to silence this warning
> 1132 | struct drm_crtc_state *crtc_state;
> | ^
> | = NULL
>
> The bug is real, but the suggestion from clang to set it to NULL is
> unfortunately just as harmful as dereferencing a NULL pointer is little
> better than uninitialized data.
Having no plane->crtc is a valid setting and it is handled inside
drm_atomic_helper_check_plane_state() by setting plane_state->visible =
false and returning early. Setting crtc_state to NULL is a correct fix.
Could you please send it?
>
> Change the function to return an error in this case.
>
> Fixes: 774bcfb73176 ("drm/msm/dpu: add support for virtual planes")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
--
With best wishes
Dmitry
On Thu, Aug 07, 2025 at 11:09:38AM +0300, Dmitry Baryshkov wrote: > Having no plane->crtc is a valid setting and it is handled inside > drm_atomic_helper_check_plane_state() by setting plane_state->visible = > false and returning early. Setting crtc_state to NULL is a correct fix. > Could you please send it? I sent this fix three weeks ago, could this be applied? https://lore.kernel.org/20250715-drm-msm-fix-const-uninit-warning-v1-1-d6a366fd9a32@kernel.org/ Cheers, Nathan
On Thu, Aug 07, 2025 at 07:34:44AM -0700, Nathan Chancellor wrote: > On Thu, Aug 07, 2025 at 11:09:38AM +0300, Dmitry Baryshkov wrote: > > Having no plane->crtc is a valid setting and it is handled inside > > drm_atomic_helper_check_plane_state() by setting plane_state->visible = > > false and returning early. Setting crtc_state to NULL is a correct fix. > > Could you please send it? > > I sent this fix three weeks ago, could this be applied? It will be picked up for -rc2 (hopefully) > > https://lore.kernel.org/20250715-drm-msm-fix-const-uninit-warning-v1-1-d6a366fd9a32@kernel.org/ > > Cheers, > Nathan -- With best wishes Dmitry
On Sat, Aug 09, 2025 at 11:20:34AM +0300, Dmitry Baryshkov wrote: > On Thu, Aug 07, 2025 at 07:34:44AM -0700, Nathan Chancellor wrote: > > On Thu, Aug 07, 2025 at 11:09:38AM +0300, Dmitry Baryshkov wrote: > > > Having no plane->crtc is a valid setting and it is handled inside > > > drm_atomic_helper_check_plane_state() by setting plane_state->visible = > > > false and returning early. Setting crtc_state to NULL is a correct fix. > > > Could you please send it? > > > > I sent this fix three weeks ago, could this be applied? > > It will be picked up for -rc2 (hopefully) Great, thank you! Even if it slips to -rc3, no worries, as long it is in the pipeline to get there. Cheers, Nathan
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