Re: [PATCH] drm/amdkfd: fix a potential NULL pointer dereference

[Kuehling, Felix]

On 2019-09-18 12:30 p.m., Allen Pais wrote:
> alloc_workqueue is not checked for errors and as a result,
> a potential NULL dereference could occur.
>
> Signed-off-by: Allen Pais <allen.pais@xxxxxxxxxx>
> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c b/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c
> index c56ac47..caa82a8 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c
> @@ -62,6 +62,11 @@ int kfd_interrupt_init(struct kfd_dev *kfd)
>   	}
>   
>   	kfd->ih_wq = alloc_workqueue("KFD IH", WQ_HIGHPRI, 1);
> +	if (unlikely(!kfd->ih_wq)) {
> +		fifo_free(&kfd->ih_fifo);

This does not compile. I think this should be kfifo_free.

> +		dev_err(kfd_chardev(), "Failed to allocate KFD IH workqueue\n");
> +		return kfd->ih_wq;

This throws a compiler warning "return makes integer from pointer 
without a cast". What's worse, kfd->ih_wq is NULL here and 
kfd_interrupt_init returns 0 to mean success, so returning a NULL 
pointer is definitely not what you want here. This function should 
return a negative error code on failure. I propose -ENOMEM.

I'm going to apply your patch with those fixes.

Regards,
 Â Felix


> +	}
>   	spin_lock_init(&kfd->interrupt_lock);
>   
>   	INIT_WORK(&kfd->interrupt_work, interrupt_wq);