linux-kernel - Re: [PATCH][next] drm/amdkfd: fix null pointer dereference on dev

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Date:   Wed, 29 May 2019 21:29:58 +0000
From:   "Kuehling, Felix" <Felix.Kuehling@....com>
To:     Colin King <colin.king@...onical.com>,
        Oded Gabbay <oded.gabbay@...il.com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        "Zhou, David(ChunMing)" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "Zeng, Oak" <Oak.Zeng@....com>
CC:     "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][next] drm/amdkfd: fix null pointer dereference on dev

On 2019-05-29 11:07 a.m., Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
>
> The pointer dev is set to null yet it is being dereferenced when
> checking dev->dqm->sched_policy.  Fix this by performing the check
> on dev->dqm->sched_policy after dev has been assigned and null
> checked.  Also remove the redundant null assignment to dev.
>
> Addresses-Coverity: ("Explicit null dereference")
> Fixes: 1a058c337676 ("drm/amdkfd: New IOCTL to allocate queue GWS")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>

Reviewed-by: Felix Kuehling <Felix.Kuehling@....com>

Thanks!

   Felix

> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
> index aab2aa6c1dee..ea82828fdc76 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
> @@ -1572,10 +1572,9 @@ static int kfd_ioctl_alloc_queue_gws(struct file *filep,
>   {
>   	int retval;
>   	struct kfd_ioctl_alloc_queue_gws_args *args = data;
> -	struct kfd_dev *dev = NULL;
> +	struct kfd_dev *dev;
>   
> -	if (!hws_gws_support ||
> -		dev->dqm->sched_policy == KFD_SCHED_POLICY_NO_HWS)
> +	if (!hws_gws_support)
>   		return -EINVAL;
>   
>   	dev = kfd_device_by_id(args->gpu_id);
> @@ -1583,6 +1582,8 @@ static int kfd_ioctl_alloc_queue_gws(struct file *filep,
>   		pr_debug("Could not find gpu id 0x%x\n", args->gpu_id);
>   		return -EINVAL;
>   	}
> +	if (dev->dqm->sched_policy == KFD_SCHED_POLICY_NO_HWS)
> +		return -EINVAL;
>   
>   	mutex_lock(&p->mutex);
>   	retval = pqm_set_gws(&p->pqm, args->queue_id, args->num_gws ? dev->gws : NULL);