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SubjectRe: [PATCH 01/24] fix default __strnlen_user macro
On 01/09/11 07:26, Mark Salter wrote:
> The existing __strnlen_user macro simply resolved to strnlen. However, the
> count returned by strnlen_user should include the NULL byte. This patch
> fixes the __strnlen_user macro to include the NULL byte in the count.
>
> Signed-off-by: Mark Salter<msalter@redhat.com>
> ---
> include/asm-generic/uaccess.h | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
> index ac68c99..1d0fdf8 100644
> --- a/include/asm-generic/uaccess.h
> +++ b/include/asm-generic/uaccess.h
> @@ -289,7 +289,7 @@ strncpy_from_user(char *dst, const char __user *src, long count)
> * Return 0 on exception, a value greater than N if too long
> */
> #ifndef __strnlen_user
> -#define __strnlen_user strnlen
> +#define __strnlen_user(s, n) (strnlen((s), (n)) + 1)
> #endif

I don't think this is correct because if you hit maxlen you will add one
to it. e.g. __strnlen_user("abcd\0", 3) would return 4 instead of 3.

It should probably be something like this:

#define __strnlen_user(s, n) ({ \
size_t k = strnlen(s, n); \
k< n ? k + 1 : n; })


I wonder if this change will break anything since it has been incorrect
(according to the comment in uaccess.h at least) for a while. Why does
__strnlen_user have different semantics to strnlen anway?

~Ryan




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