[PATCH v2] drm/amdgpu: Fix cat debugfs amdgpu_regs_didt causes kernel null pointer

[Christian König]

Am 23.11.23 um 02:22 schrieb Lu Yao:
> For 'AMDGPU_FAMILY_SI' family cards, in 'si_common_early_init' func, init
> 'didt_rreg' and 'didt_wreg' to 'NULL'. But in func
> 'amdgpu_debugfs_regs_didt_read/write', using 'RREG32_DIDT' 'WREG32_DIDT'
> lacks of relevant judgment. And other 'amdgpu_ip_block_version' that use
> these two definitions won't be added for 'AMDGPU_FAMILY_SI'.
>
> So, add null pointer judgment before calling.
>
> Signed-off-by: Lu Yao <yaolu at kylinos.cn>

Reviewed-by: Christian König <christian.koenig at amd.com>

> ---
> Changes in v2:
>    1. Drop dev_err message.
>    2. Change error code from 'EPERM' to 'EOPNOTSUPP'
> Link to v1: https://lore.kernel.org/all/20231122093509.34302-1-yaolu@kylinos.cn/
> Thanks Christian for his comments.
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> index a53f436fa9f1..e098cd66fa2a 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> @@ -638,6 +638,9 @@ static ssize_t amdgpu_debugfs_regs_didt_read(struct file *f, char __user *buf,
>   	if (size & 0x3 || *pos & 0x3)
>   		return -EINVAL;
>   
> +	if (adev->didt_rreg == NULL)
> +		return -EOPNOTSUPP;
> +
>   	r = pm_runtime_get_sync(adev_to_drm(adev)->dev);
>   	if (r < 0) {
>   		pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);
> @@ -694,6 +697,9 @@ static ssize_t amdgpu_debugfs_regs_didt_write(struct file *f, const char __user
>   	if (size & 0x3 || *pos & 0x3)
>   		return -EINVAL;
>   
> +	if (adev->didt_wreg == NULL)
> +		return -EOPNOTSUPP;
> +
>   	r = pm_runtime_get_sync(adev_to_drm(adev)->dev);
>   	if (r < 0) {
>   		pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);