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Thu, 07 Aug 2025 03:34:52 -0700 (PDT) Date: Thu, 7 Aug 2025 13:34:48 +0300 From: Dan Carpenter To: Chenyuan Yang Cc: Maxime Ripard , wens@csie.org, maarten.lankhorst@linux.intel.com, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, jernej.skrabec@gmail.com, samuel@sholland.org, neil.armstrong@linaro.org, dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drm/sun4i: backend: Fix error pointers in sun4i_backend_atomic_check Message-ID: References: <20250314012029.668306-1-chenyuan0y@gmail.com> <20250314-prophetic-attentive-platypus-3ab214@houat> Precedence: bulk X-Mailing-List: linux-sunxi@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Fri, Mar 14, 2025 at 11:00:26AM -0500, Chenyuan Yang wrote: > HI Maxime. > > Thanks so much for pointing that out! > > How about such a patch? > This patch is corrupted so we can't review it. > diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.c > b/drivers/gpu/drm/sun4i/sun4i_backend.c > index 2dded3b828df..5ad0e90d3e6b 100644 > --- a/drivers/gpu/drm/sun4i/sun4i_backend.c > +++ b/drivers/gpu/drm/sun4i/sun4i_backend.c > @@ -490,9 +490,14 @@ static int sun4i_backend_atomic_check(struct > sunxi_engine *engine, > drm_for_each_plane_mask(plane, drm, crtc_state->plane_mask) { > struct drm_plane_state *plane_state = > drm_atomic_get_plane_state(state, plane); > - struct sun4i_layer_state *layer_state = > - state_to_sun4i_layer_state(plane_state); > - struct drm_framebuffer *fb = plane_state->fb; > + struct sun4i_layer_state *layer_state = NULL; > + struct drm_framebuffer *fb = NULL; No need to initialize things like this. NULL isn't a valid pointer. This just disables static checker tools from finding uninitialized variable warnings so all the expense of writing the checker tools is now wasted. regards, dan carpenter > + > + if (IS_ERR(plane_state)) > + return PTR_ERR(plane_state); > + > + layer_state = state_to_sun4i_layer_state(plane_state); > + fb = plane_state->fb; > > if (!sun4i_backend_plane_is_supported(plane_state, > &layer_state->uses_frontend)) > -- > > -Chenyuan > > On Fri, Mar 14, 2025 at 2:17 AM Maxime Ripard wrote: > > > > Hi, > > > > On Thu, Mar 13, 2025 at 08:20:29PM -0500, Chenyuan Yang wrote: > > > The function sun4i_backend_atomic_check was dereferencing pointers > > > returned by drm_atomic_get_plane_state without checking for errors. This > > > could lead to undefined behavior if the function returns an error pointer. > > > > > > This commit adds checks using IS_ERR to ensure that plane_state is > > > valid before dereferencing them. > > > > > > Similar to commit da29abe71e16 > > > ("drm/amd/display: Fix error pointers in amdgpu_dm_crtc_mem_type_changed"). > > > > > > Fixes: 96180dde23b7 ("drm/sun4i: backend: Add a custom atomic_check for the frontend") > > > Signed-off-by: Chenyuan Yang > > > --- > > > drivers/gpu/drm/sun4i/sun4i_backend.c | 4 ++++ > > > 1 file changed, 4 insertions(+) > > > > > > diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.c b/drivers/gpu/drm/sun4i/sun4i_backend.c > > > index 2dded3b828df..a8e0e2123764 100644 > > > --- a/drivers/gpu/drm/sun4i/sun4i_backend.c > > > +++ b/drivers/gpu/drm/sun4i/sun4i_backend.c > > > @@ -490,6 +490,10 @@ static int sun4i_backend_atomic_check(struct sunxi_engine *engine, > > > drm_for_each_plane_mask(plane, drm, crtc_state->plane_mask) { > > > struct drm_plane_state *plane_state = > > > drm_atomic_get_plane_state(state, plane); > > > + > > > + if (IS_ERR(plane_state)) > > > + return PTR_ERR(plane_state); > > > + > > > > This introduces a build warning. You shouldn't mix declarations and code. > > > > Maxime