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Message-ID: <70f001cd-eaec-874f-9742-c44e66368a2a@acm.org>
Date: Sat, 18 Apr 2020 08:40:20 -0700
From: Bart Van Assche <bvanassche@....org>
To: Jan Kara <jack@...e.cz>, Christoph Hellwig <hch@....de>
Cc: axboe@...nel.dk, yuyufen@...wei.com, tj@...nel.org, tytso@....edu,
gregkh@...uxfoundation.org, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/8] bdi: add a ->dev_name field to struct
backing_dev_info
On 2020-04-17 01:59, Jan Kara wrote:
> On Thu 16-04-20 18:54:48, Christoph Hellwig wrote:
>> @@ -938,7 +938,8 @@ int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
>> if (bdi->dev) /* The driver needs to use separate queues per device */
>> return 0;
>>
>> - dev = device_create_vargs(bdi_class, NULL, MKDEV(0, 0), bdi, fmt, args);
>> + vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
>> + dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
>> if (IS_ERR(dev))
>> return PTR_ERR(dev);
>>
>
> This can have a sideeffect not only bdi->dev_name will be truncated to 64
> chars (which generally doesn't matter) but possibly also kobject name will
> be truncated in the same way. Which may have user visible effects. E.g.
> for fs/vboxsf 64 chars need not be enough. So shouldn't we rather do it the
> other way around - i.e., let device_create_vargs() create the device name
> and then copy to bdi->dev_name whatever fits?
How about using kvasprintf() instead of vsnprintf()?
Thanks,
Bart.
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