linux-kernel - Re: [PATCH 1/1] drm/amdkfd: Create file descriptor after client is added to smi

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Message-ID: <a85f7751-8e60-d8f4-a281-4fb50389ae7e@amd.com>
Date:   Wed, 30 Mar 2022 12:29:53 -0400
From:   Felix Kuehling <felix.kuehling@....com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     linux-kernel@...r.kernel.org,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 1/1] drm/amdkfd: Create file descriptor after client is
 added to smi_clients list


Am 2022-03-30 um 03:51 schrieb Lee Jones:
> This ensures userspace cannot prematurely clean-up the client before
> it is fully initialised which has been proven to cause issues in the
> past.
>
> Cc: Felix Kuehling <Felix.Kuehling@....com>
> Cc: Alex Deucher <alexander.deucher@....com>
> Cc: "Christian König" <christian.koenig@....com>
> Cc: "Pan, Xinhui" <Xinhui.Pan@....com>
> Cc: David Airlie <airlied@...ux.ie>
> Cc: Daniel Vetter <daniel@...ll.ch>
> Cc: amd-gfx@...ts.freedesktop.org
> Cc: dri-devel@...ts.freedesktop.org
> Signed-off-by: Lee Jones <lee.jones@...aro.org>
> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_smi_events.c | 18 +++++++++---------
>   1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_smi_events.c b/drivers/gpu/drm/amd/amdkfd/kfd_smi_events.c
> index e4beebb1c80a2..c5d5398d45cbf 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_smi_events.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_smi_events.c
> @@ -247,15 +247,6 @@ int kfd_smi_event_open(struct kfd_dev *dev, uint32_t *fd)
>   		return ret;
>   	}
>   
> -	ret = anon_inode_getfd(kfd_smi_name, &kfd_smi_ev_fops, (void *)client,
> -			       O_RDWR);
> -	if (ret < 0) {
> -		kfifo_free(&client->fifo);
> -		kfree(client);
> -		return ret;
> -	}
> -	*fd = ret;
> -
>   	init_waitqueue_head(&client->wait_queue);
>   	spin_lock_init(&client->lock);
>   	client->events = 0;
> @@ -265,5 +256,14 @@ int kfd_smi_event_open(struct kfd_dev *dev, uint32_t *fd)
>   	list_add_rcu(&client->list, &dev->smi_clients);
>   	spin_unlock(&dev->smi_lock);
>   
> +	ret = anon_inode_getfd(kfd_smi_name, &kfd_smi_ev_fops, (void *)client,
> +			       O_RDWR);
> +	if (ret < 0) {

Thank you for the patch. This looks like the correct solution. But you 
also need to remove the client from the dev->smi_clients list here 
before kfree(client). With that fixed, the patch is

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


> +		kfifo_free(&client->fifo);
> +		kfree(client);
> +		return ret;
> +	}
> +	*fd = ret;
> +
>   	return 0;
>   }