2022-02-18 19:51:45

by Souptick Joarder

Subject: [PATCH] drm/amdgpu: Initialize value of r in amdgpu_fill_buffer()

From: "Souptick Joarder (HPE)" <[email protected]>

Kernel test robot reported warning ->
drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c:2129:2: warning: Undefined
or garbage value returned to caller [clang-analyzer-core.
uninitialized.UndefReturn]

Initialize r inside amdgpu_fill_buffer().

Reported-by: kernel test robot <[email protected]>
Signed-off-by: Souptick Joarder (HPE) <[email protected]>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 414a22dddc78..5fafb223177f 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -2089,7 +2089,7 @@ int amdgpu_fill_buffer(struct amdgpu_bo *bo,
struct amdgpu_ring *ring = adev->mman.buffer_funcs_ring;
struct dma_fence *fence = NULL;
struct amdgpu_res_cursor dst;
- int r;
+ int r = 0;

if (!adev->mman.buffer_funcs_enabled) {
DRM_ERROR("Trying to clear memory with ring turned off.\n");
--
2.25.1

2022-02-21 08:06:51

by Christian König

Subject: Re: [PATCH] drm/amdgpu: Initialize value of r in amdgpu_fill_buffer()

Am 18.02.22 um 19:53 schrieb Souptick Joarder:
> From: "Souptick Joarder (HPE)" <[email protected]>
>
> Kernel test robot reported warning ->
> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c:2129:2: warning: Undefined
> or garbage value returned to caller [clang-analyzer-core.
> uninitialized.UndefReturn]

Good catch, but that fix is usually seen as bad practice.

The warning is a false positive because the code path which would lead
to returning an undefined value can never happen. There is just no way
the compiler could know that.

I suggest to better initialize the return value directly before the
error handling to indicate that when we have reached this point we can
return success safely.

Regards,
Christian.

>
> Initialize r inside amdgpu_fill_buffer().
>
> Reported-by: kernel test robot <[email protected]>
> Signed-off-by: Souptick Joarder (HPE) <[email protected]>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 414a22dddc78..5fafb223177f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -2089,7 +2089,7 @@ int amdgpu_fill_buffer(struct amdgpu_bo *bo,
> struct amdgpu_ring *ring = adev->mman.buffer_funcs_ring;
> struct dma_fence *fence = NULL;
> struct amdgpu_res_cursor dst;
> - int r;
> + int r = 0;
>
> if (!adev->mman.buffer_funcs_enabled) {
> DRM_ERROR("Trying to clear memory with ring turned off.\n");