Subject: Re: [PATH 0/2] strndup_user, description
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Davi Arnaut <davi.arnaut@gmail.com>
Cc: akpm@osdl.org, linux-kernel@vger.kernel.org
In-Reply-To: <20060214214747.ef05e4d8.davi.arnaut@gmail.com>
References: <20060214214747.ef05e4d8.davi.arnaut@gmail.com>
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Date: Wed, 15 Feb 2006 02:53:10 +0000
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On Maw, 2006-02-14 at 21:47 -0300, Davi Arnaut wrote:
> This patch series creates a strndup_user() function in order to avoid duplicated
> and error-prone (userspace modifying the string after the strlen_user()) code.

Well userspace can still modify in this case. So you could still get a
\0 mid buffer but that seems harmless.

However

> +#define strdup_user(s)	strndup_user(s, PAGE_SIZE)

Better this doesn't exist as it is a wrapper for a bad habit that isnt
yet used so why encourage it.


> +	length = strlen_user(s);

What if n is very large ? Should use strnlen_user clipped by n

Also say the length limit is 8 and the text is "hello\0"

We get length = 5  5 < 8, alloc 5 bytes set 5th to \0 and return "hell
\0"


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