On Wed, 15 Feb 2006 02:53:10 +0000
Alan Cox <[email protected]> wrote:
> 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.
Yes.
> 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.
>
Ok, I will inline it.
>
> > + length = strlen_user(s);
>
> What if n is very large ? Should use strnlen_user clipped by n
That's what "if (length > n) length = n" is for.
> 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"
No, we would get length = 6, strlen_user returns the size of the string
_including_ the terminating NUL.
--
Davi Arnaut
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