linux-kernel - Re: [PATCH v2 2/6] mdev: Make mdev alias unique among all mdevs

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Date:   Thu, 29 Aug 2019 20:31:29 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Parav Pandit <parav@...lanox.com>, <alex.williamson@...hat.com>,
        <jiri@...lanox.com>, <kwankhede@...dia.com>, <cohuck@...hat.com>,
        <davem@...emloft.net>
CC:     <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 2/6] mdev: Make mdev alias unique among all mdevs

On 2019/8/29 19:19, Parav Pandit wrote:
> Mdev alias should be unique among all the mdevs, so that when such alias
> is used by the mdev users to derive other objects, there is no
> collision in a given system.
> 
> Signed-off-by: Parav Pandit <parav@...lanox.com>
> 
> ---
> Changelog:
> v1->v2:
>  - Moved alias NULL check at beginning
> v0->v1:
>  - Fixed inclusiong of alias for NULL check
>  - Added ratelimited debug print for sha1 hash collision error
> ---
>  drivers/vfio/mdev/mdev_core.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
> index 3bdff0469607..c9bf2ac362b9 100644
> --- a/drivers/vfio/mdev/mdev_core.c
> +++ b/drivers/vfio/mdev/mdev_core.c
> @@ -388,6 +388,13 @@ int mdev_device_create(struct kobject *kobj, struct device *dev,
>  			ret = -EEXIST;
>  			goto mdev_fail;
>  		}
> +		if (alias && tmp->alias && strcmp(alias, tmp->alias) == 0) {

!strcmp(alias, tmp->alias) is a more common kernel pattern.

Also if we limit max len of the alias in patch 1, maybe use that to limit the
string compare too.

> +			mutex_unlock(&mdev_list_lock);
> +			ret = -EEXIST;
> +			dev_dbg_ratelimited(dev, "Hash collision in alias creation for UUID %pUl\n",
> +					    uuid);
> +			goto mdev_fail;
> +		}
>  	}
>  
>  	mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
>