Re: [PATCH] drm/i915: Check input parameter for NULL

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Hi,

On 22/02/2022 14:46, Yongzhi Liu wrote:
[why]
i915_gem_object_put_pages_phys() frees pages and standard
pattern is to allow caller to not care if it's
NULL or not. This will reduce burden on
the callers to perform this check.

I don't think we want this in general, and definitely not just for phys objects and leaving others not handle NULL.

See comment at the call site for these vfuncs:

	/*
	 * XXX Temporary hijinx to avoid updating all backends to handle
	 * NULL pages. In the future, when we have more asynchronous
	 * get_pages backends we should be better able to handle the
	 * cancellation of the async task in a more uniform manner.
	 */
	if (!IS_ERR_OR_NULL(pages))
		obj->ops->put_pages(obj, pages);

Maarten owns this area these days so he can comment as well.

Regards,

Tvrtko

[how]
Fix it by adding Null check.

Signed-off-by: Yongzhi Liu <lyz_cs@xxxxxxxxxx>
---
  drivers/gpu/drm/i915/gem/i915_gem_phys.c | 8 ++++++--
  1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_phys.c b/drivers/gpu/drm/i915/gem/i915_gem_phys.c
index ca6faff..09c3dcb 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_phys.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_phys.c
@@ -95,8 +95,13 @@ void
  i915_gem_object_put_pages_phys(struct drm_i915_gem_object *obj,
  			       struct sg_table *pages)
  {
-	dma_addr_t dma = sg_dma_address(pages->sgl);
-	void *vaddr = sg_page(pages->sgl);
+	dma_addr_t dma;
+	void *vaddr;
+
+	if (!pages)
+		return;
+	dma = sg_dma_address(pages->sgl);
+	vaddr = sg_page(pages->sgl);
__i915_gem_object_release_shmem(obj, pages, false);



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