linux-kernel - Re: [RFC] prctl: Deprecate non PR_SET_MM

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Message-ID: <48bcd917-4eb8-9da6-ec4b-e76a654695c4@linux.alibaba.com>
Date:   Tue, 3 Apr 2018 16:15:20 -0700
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     Cyrill Gorcunov <gorcunov@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Andrey Vagin <avagin@...nvz.org>,
        Andrew Morton <akpm@...uxfoundation.org>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Michal Hocko <mhocko@...nel.org>
Subject: Re: [RFC] prctl: Deprecate non PR_SET_MM_MAP operations



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@...nvz.org>
> CC: Andrew Morton <akpm@...uxfoundation.org>
> CC: Pavel Emelyanov <xemul@...tuozzo.com>
> CC: Michael Kerrisk <mtk.manpages@...il.com>
> CC: Yang Shi <yang.shi@...ux.alibaba.com>
> CC: Michal Hocko <mhocko@...nel.org>
> Signed-off-by: Cyrill Gorcunov <gorcunov@...il.com>
> ---
> 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);
>