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SubjectRe: [PATCH v06 05/36] uapi linux/sysctl.h: use __kernel_size_t instead of size_t
On Sun, Aug 06, 2017 at 06:43:56PM +0200, Mikko Rapeli wrote:
> Fixes userspace compilation error:
>
> error: unknown type name ‘size_t’
>
> Signed-off-by: Mikko Rapeli <mikko.rapeli@iki.fi>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: David S. Miller <davem@davemloft.net>
> ---
> include/uapi/linux/sysctl.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/uapi/linux/sysctl.h b/include/uapi/linux/sysctl.h
> index e13d48058b8d..35a4b8b417fe 100644
> --- a/include/uapi/linux/sysctl.h
> +++ b/include/uapi/linux/sysctl.h
> @@ -35,9 +35,9 @@ struct __sysctl_args {
> int __user *name;
> int nlen;
> void __user *oldval;
> - size_t __user *oldlenp;
> + __kernel_size_t __user *oldlenp;
> void __user *newval;
> - size_t newlen;
> + __kernel_size_t newlen;
> unsigned long __unused[4];
> };

You should be extremely careful when replacing size_t with __kernel_size_t
because e.g. on x32 you have sizeof(size_t) < sizeof(__kernel_size_t).

In case of sysctl.h this replacement would be wrong.

I submitted an alternative fix for this bug some time ago, see
http://lkml.kernel.org/r/20170222230652.GA14373@altlinux.org


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