2022-02-22 18:34:34

by Yongzhi Liu

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

[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.

[how]
Fix it by adding Null check.

Signed-off-by: Yongzhi Liu <[email protected]>
---
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);

--
2.7.4

2022-02-22 20:01:07

by Tvrtko Ursulin

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

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 <[email protected]>
> ---
> 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);
>