Re: [RFC] prctl: Deprecate non PR_SET_MM_MAP operations

[Yang Shi]

On 4/3/18 3:37 PM, Cyrill Gorcunov wrote:
> An ability to manipulate mm_struct fields was introduced in
> sake of CRIU in first place. Later we provide more suitable
> and safe operation PR_SET_MM_MAP where all fields to be modifed
> are passed in one structure which allows us to make more detailed
> verification.
>
> Still old interface remains present for compatibility reason
> though CRIU itself already switched to PR_SET_MM_MAP on its
> own long ago.
>
> Googling didn't reveal some other users of this operation
> so I think it should be safe to issue deprecation warning
> first time and get rid of this interface after a couple
> of releases.
>
> CC: Andrey Vagin <avagin@xxxxxxxxxx>
> CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxx>
> CC: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
> CC: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
> CC: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
> CC: Michal Hocko <mhocko@xxxxxxxxxx>
> Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
> ---
> Or we can simply drop it off because PR_SET_MM_MAP covers all needs,
> and I would rather prefer to do that asap.

Thanks for making it deprecated. I'd prefer just drop it off if nobody 
objects. The change will get soaked in linux-next for a while , we will 
know if it breaks compatibility (it sounds very unlikely).

Yang

>   kernel/sys.c |    2 ++
>   1 file changed, 2 insertions(+)
>
> Index: linux-ml.git/kernel/sys.c
> ===================================================================
> --- linux-ml.git.orig/kernel/sys.c
> +++ linux-ml.git/kernel/sys.c
> @@ -2052,6 +2052,8 @@ static int prctl_set_mm(int opt, unsigne
>   	if (!capable(CAP_SYS_RESOURCE))
>   		return -EPERM;
>   
> +	pr_warn_once("Non PR_SET_MM_MAP operations are deprecated\n");
> +
>   	if (opt == PR_SET_MM_EXE_FILE)
>   		return prctl_set_mm_exe_file(mm, (unsigned int)addr);
>