[PATCH] drm/amd/amdgpu: Fix GPR read from debugfs (v2)

[Alex Deucher]

On Wed, Mar 11, 2020 at 4:33 PM Tom St Denis <tom.stdenis at amd.com> wrote:
>
> The offset into the array was specified in bytes but should
> be in terms of 32-bit words.  Also prevent large reads that
> would also cause a buffer overread.
>
> v2:  Read from correct offset from internal storage buffer.
>
> Signed-off-by: Tom St Denis <tom.stdenis at amd.com>
> Acked-by: Christian König <christian.koenig at amd.com>

Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> index 00942afc4e13..02bb1be11ffe 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> @@ -784,11 +784,11 @@ static ssize_t amdgpu_debugfs_gpr_read(struct file *f, char __user *buf,
>         ssize_t result = 0;
>         uint32_t offset, se, sh, cu, wave, simd, thread, bank, *data;
>
> -       if (size & 3 || *pos & 3)
> +       if (size > 4096 || size & 3 || *pos & 3)
>                 return -EINVAL;
>
>         /* decode offset */
> -       offset = *pos & GENMASK_ULL(11, 0);
> +       offset = (*pos & GENMASK_ULL(11, 0)) >> 2;
>         se = (*pos & GENMASK_ULL(19, 12)) >> 12;
>         sh = (*pos & GENMASK_ULL(27, 20)) >> 20;
>         cu = (*pos & GENMASK_ULL(35, 28)) >> 28;
> @@ -826,7 +826,7 @@ static ssize_t amdgpu_debugfs_gpr_read(struct file *f, char __user *buf,
>         while (size) {
>                 uint32_t value;
>
> -               value = data[offset++];
> +               value = data[result >> 2];
>                 r = put_user(value, (uint32_t *)buf);
>                 if (r) {
>                         result = r;
> --
> 2.24.1
>
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