linux-kernel - Re: sysfs_ops show vector: size of buffer not required?

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Message-ID: <20100126043646.GB32066@kroah.com>
Date:	Mon, 25 Jan 2010 20:36:46 -0800
From:	Greg KH <greg@...ah.com>
To:	Himanshu Chauhan <himanshu@...metricore.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Kernel Newbies <kernelnewbies@...linux.org>
Subject: Re: sysfs_ops show vector: size of buffer not required?

On Sun, Jan 24, 2010 at 01:11:18PM +0530, Himanshu Chauhan wrote:
> Hi All,
> 
> The sysfs_ops's show vector doesn't have a size of the
> buffer given to the vector, while store on the other hand
> has. What is the rationale behind it?

If you need to check the size, you are doing something wrong.

Seriously, that is the reason.  A sysfs file should be a single value,
which will never overflow the buffer.

> I see most of the implementations doing strcpy in the
> show vectors. Ill behaved driver might overwrite the
> given buffer when size is not known. Should this be addressed
> by providing the buffer size along with the buffer pointer?

Nope.

Again, a single value only, it easily fits into the buffer size.

thanks,

greg k-h
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