[PATCH] drm/exynos: gsc: allocate formats as a flexible array member

[Rosen Penev]

The formats array is allocated separately with devm_kcalloc() and only
referenced through the gsc_context. Make it a flexible array member at
the end of the context and allocate both in one go with struct_size().

Annotate it with __counted_by(num_formats) so the array accesses can be
bounds checked with FORTIFY_SOURCE and UBSAN_BOUNDS.

Assisted-by: LLM
Signed-off-by: Rosen Penev <rosenp at gmail.com>
---
 drivers/gpu/drm/exynos/exynos_drm_gsc.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_gsc.c b/drivers/gpu/drm/exynos/exynos_drm_gsc.c
index d9637ddfcfc4..f1807ef664e1 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_gsc.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_gsc.c
@@ -99,7 +99,6 @@ struct gsc_context {
 	void		*dma_priv;
 	struct device	*dev;
 	struct exynos_drm_ipp_task	*task;
-	struct exynos_drm_ipp_formats	*formats;
 	unsigned int			num_formats;
 
 	void __iomem	*regs;
@@ -110,6 +109,7 @@ struct gsc_context {
 	int	id;
 	int	irq;
 	bool	rotation;
+	struct exynos_drm_ipp_formats	formats[] __counted_by(num_formats);
 };
 
 /**
@@ -1222,21 +1222,19 @@ static int gsc_probe(struct platform_device *pdev)
 	struct gsc_context *ctx;
 	int num_formats, ret, i, j;
 
-	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
+	num_formats = ARRAY_SIZE(gsc_formats) + ARRAY_SIZE(gsc_tiled_formats);
+	ctx = devm_kzalloc(dev, struct_size(ctx, formats, num_formats), GFP_KERNEL);
 	if (!ctx)
 		return -ENOMEM;
 
+	ctx->num_formats = num_formats;
+	formats = ctx->formats;
+
 	driver_data = device_get_match_data(dev);
 	ctx->dev = dev;
 	ctx->num_clocks = driver_data->num_clocks;
 	ctx->clk_names = driver_data->clk_names;
 
-	/* construct formats/limits array */
-	num_formats = ARRAY_SIZE(gsc_formats) + ARRAY_SIZE(gsc_tiled_formats);
-	formats = devm_kcalloc(dev, num_formats, sizeof(*formats), GFP_KERNEL);
-	if (!formats)
-		return -ENOMEM;
-
 	/* linear formats */
 	for (i = 0; i < ARRAY_SIZE(gsc_formats); i++) {
 		formats[i].fourcc = gsc_formats[i];
@@ -1256,9 +1254,6 @@ static int gsc_probe(struct platform_device *pdev)
 		formats[j].num_limits = driver_data->num_limits;
 	}
 
-	ctx->formats = formats;
-	ctx->num_formats = num_formats;
-
 	/* clock control */
 	for (i = 0; i < ctx->num_clocks; i++) {
 		ctx->clocks[i] = devm_clk_get(dev, ctx->clk_names[i]);
-- 
2.56.0