Re: [PATCH v1 2/2] drm/sprd: fix potential NULL dereference

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Hi,

on the changes for platform_get_resource(), you can

Acked-by: Thomas Zimmermann <tzimmermann@xxxxxxx>

but see my comments below.

Am 24.12.21 um 15:12 schrieb Kevin Tang:
platform_get_resource() may fail and return NULL, so check it's value
before using it.

'drm' could be null in sprd_drm_shutdown, and drm_warn maybe dereference
it, remove this warning log.

Cc: Orson Zhai <orsonzhai@xxxxxxxxx>
Cc: Chunyan Zhang <zhang.lyra@xxxxxxxxx>
Signed-off-by: Kevin Tang <kevin.tang@xxxxxxxxxx>
---
  drivers/gpu/drm/sprd/sprd_dpu.c | 3 +++
  drivers/gpu/drm/sprd/sprd_drm.c | 8 ++------
  drivers/gpu/drm/sprd/sprd_dsi.c | 3 +++
  3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/sprd/sprd_dpu.c b/drivers/gpu/drm/sprd/sprd_dpu.c
index 06a3414ee..69683b7ba 100644
--- a/drivers/gpu/drm/sprd/sprd_dpu.c
+++ b/drivers/gpu/drm/sprd/sprd_dpu.c
@@ -790,6 +790,9 @@ static int sprd_dpu_context_init(struct sprd_dpu *dpu,
  	int ret;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -EINVAL;
+

You can add an error message if this fails.


  	ctx->base = devm_ioremap(dev, res->start, resource_size(res));
  	if (!ctx->base) {
  		dev_err(dev, "failed to map dpu registers\n");
diff --git a/drivers/gpu/drm/sprd/sprd_drm.c b/drivers/gpu/drm/sprd/sprd_drm.c
index a077e2d4d..54030839e 100644
--- a/drivers/gpu/drm/sprd/sprd_drm.c
+++ b/drivers/gpu/drm/sprd/sprd_drm.c
@@ -154,12 +154,8 @@ static void sprd_drm_shutdown(struct platform_device *pdev)
  {
  	struct drm_device *drm = platform_get_drvdata(pdev);
- if (!drm) {
-		drm_warn(drm, "drm device is not available, no shutdown\n");
-		return;
-	}
-
-	drm_atomic_helper_shutdown(drm);
+	if (drm)
+		drm_atomic_helper_shutdown(drm);

This change should be in a separate patch. Instead of removing the warning, you should rather use dev_err() or dev_warn() from [1]. Not being able to shut down here looks like a serious driver bug that the user should know about.


  }
static const struct of_device_id drm_match_table[] = {
diff --git a/drivers/gpu/drm/sprd/sprd_dsi.c b/drivers/gpu/drm/sprd/sprd_dsi.c
index 911b3cddc..955c5995a 100644
--- a/drivers/gpu/drm/sprd/sprd_dsi.c
+++ b/drivers/gpu/drm/sprd/sprd_dsi.c
@@ -907,6 +907,9 @@ static int sprd_dsi_context_init(struct sprd_dsi *dsi,
  	struct resource *res;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -EINVAL;
+

Again, an error message seems appropriate.

Best regards
Thomas

[1] https://elixir.bootlin.com/linux/latest/source/include/linux/dev_printk.h#L145

  	ctx->base = devm_ioremap(dev, res->start, resource_size(res));
  	if (!ctx->base) {
  		drm_err(dsi->drm, "failed to map dsi host registers\n");

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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