linux-kernel - Re: [PATCHv2] drm/amdkfd: Remove vla

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Message-ID: <e71e9512-d4cf-9aa2-fef2-075833fc8e40@amd.com>
Date:   Wed, 11 Apr 2018 11:31:07 -0400
From:   Felix Kuehling <felix.kuehling@....com>
To:     Laura Abbott <labbott@...hat.com>,
        Oded Gabbay <oded.gabbay@...il.com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>
Cc:     David Airlie <airlied@...ux.ie>, dri-devel@...ts.freedesktop.org,
        amd-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel-hardening@...ts.openwall.com,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCHv2] drm/amdkfd: Remove vla

On 2018-04-10 09:02 PM, Laura Abbott wrote:
> There's an ongoing effort to remove VLAs[1] from the kernel to eventually
> turn on -Wvla. Switch to a constant value that covers all hardware.
>
> [1] https://lkml.org/lkml/2018/3/7/621
>
> Signed-off-by: Laura Abbott <labbott@...hat.com>
> ---
> v2: Switch to a larger size to account for other hardware
> ---
>  drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c b/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c
> index 035c351f47c5..c3a5a80e31ae 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c
> @@ -139,10 +139,12 @@ static void interrupt_wq(struct work_struct *work)
>  {
>  	struct kfd_dev *dev = container_of(work, struct kfd_dev,
>  						interrupt_work);
> +	uint32_t ih_ring_entry[8];
>  
> -	uint32_t ih_ring_entry[DIV_ROUND_UP(
> -				dev->device_info->ih_ring_entry_size,
> -				sizeof(uint32_t))];
> +	if (dev->device_info->ih_ring_entry_size > (8 * sizeof(uint32_t))) {
> +		dev_err(kfd_chardev(), "Ring entry too small\n");

When the ring entry size really is too small, this will potentially
flood the kernel log. Maybe a WARN_ONCE would be more helpful. With that
fixed, this patch is Reviewed-by: Felix Kuehling <Felix.Kuehling@....com>

Regards,
  Felix

> +		return;
> +	}
>  
>  	while (dequeue_ih_ring_entry(dev, ih_ring_entry))
>  		dev->device_info->event_interrupt_class->interrupt_wq(dev,