This is a note to let you know that I've just added the patch titled
drm/mediatek: Init `ddp_comp` with devm_kcalloc()
to the 6.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-mediatek-init-ddp_comp-with-devm_kcalloc.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 8903dec4902dc079e6d3288a4a54417f7ec682cc
Author: Douglas Anderson <dianders@xxxxxxxxxxxx>
Date: Thu Mar 28 09:22:49 2024 -0700
drm/mediatek: Init `ddp_comp` with devm_kcalloc()
[ Upstream commit 01a2c5123e27b3c4685bf2fc4c2e879f6e0c7b33 ]
In the case where `conn_routes` is true we allocate an extra slot in
the `ddp_comp` array but mtk_drm_crtc_create() never seemed to
initialize it in the test case I ran. For me, this caused a later
crash when we looped through the array in mtk_drm_crtc_mode_valid().
This showed up for me when I booted with `slub_debug=FZPUA` which
poisons the memory initially. Without `slub_debug` I couldn't
reproduce, presumably because the later code handles the value being
NULL and in most cases (not guaranteed in all cases) the memory the
allocator returned started out as 0.
It really doesn't hurt to initialize the array with devm_kcalloc()
since the array is small and the overhead of initting a handful of
elements to 0 is small. In general initting memory to zero is a safer
practice and usually it's suggested to only use the non-initting alloc
functions if you really need to.
Let's switch the function to use an allocation function that zeros the
memory. For me, this avoids the crash.
Fixes: 01389b324c97 ("drm/mediatek: Add connector dynamic selection capability")
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Reviewed-by: CK Hu <ck.hu@xxxxxxxxxxxx>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20240328092248.1.I2e73c38c0f264ee2fa4a09cdd83994e37ba9f541@changeid/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
index 3d17de34d72bd..d398fa1871165 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
@@ -992,10 +992,10 @@ int mtk_drm_crtc_create(struct drm_device *drm_dev,
mtk_crtc->mmsys_dev = priv->mmsys_dev;
mtk_crtc->ddp_comp_nr = path_len;
- mtk_crtc->ddp_comp = devm_kmalloc_array(dev,
- mtk_crtc->ddp_comp_nr + (conn_routes ? 1 : 0),
- sizeof(*mtk_crtc->ddp_comp),
- GFP_KERNEL);
+ mtk_crtc->ddp_comp = devm_kcalloc(dev,
+ mtk_crtc->ddp_comp_nr + (conn_routes ? 1 : 0),
+ sizeof(*mtk_crtc->ddp_comp),
+ GFP_KERNEL);
if (!mtk_crtc->ddp_comp)
return -ENOMEM;
