Date: Thu, 10 Aug 2017 17:23:52 +0200
From: Michal Hocko <mhocko@kernel.org>
To: riel@redhat.com
Cc: linux-kernel@vger.kernel.org, mike.kravetz@oracle.com,
        linux-mm@kvack.org, fweimer@redhat.com, colm@allcosts.net,
        akpm@linux-foundation.org, keescook@chromium.org, luto@amacapital.net,
        wad@chromium.org, mingo@kernel.org, kirill@shutemov.name,
        dave.hansen@intel.com
Subject: Re: [PATCH 2/2] mm,fork: introduce MADV_WIPEONFORK
Message-ID: <20170810152352.GZ23863@dhcp22.suse.cz>
References: <20170806140425.20937-1-riel@redhat.com>
 <20170806140425.20937-3-riel@redhat.com>
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On Sun 06-08-17 10:04:25, Rik van Riel wrote:
[...]
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 17921b0390b4..db1fb2802ecc 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -659,6 +659,13 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
>  		tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
>  		tmp->vm_next = tmp->vm_prev = NULL;
>  		file = tmp->vm_file;
> +
> +		/* With VM_WIPEONFORK, the child gets an empty VMA. */
> +		if (tmp->vm_flags & VM_WIPEONFORK) {
> +			tmp->vm_file = file = NULL;
> +			tmp->vm_ops = NULL;
> +		}

What about VM_SHARED/|VM)MAYSHARE flags. Is it OK to keep the around? At
least do_anonymous_page SIGBUS on !vm_ops && VM_SHARED. Or do I miss
where those flags are cleared?

> +
>  		if (file) {
>  			struct inode *inode = file_inode(file);
>  			struct address_space *mapping = file->f_mapping;
-- 
Michal Hocko
SUSE Labs