linux-kernel - Re: [PATCHv4 02/18] mm/ksm: Do not merge pages with different KeyIDs

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Date:   Mon, 9 Jul 2018 14:03:20 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv4 02/18] mm/ksm: Do not merge pages with different KeyIDs

On Tue, Jun 26, 2018 at 05:22:29PM +0300, Kirill A. Shutemov wrote:
> Pages encrypted with different encryption keys are not subject to KSM

Perhaps not allowed instead of subject?
> merge. Otherwise it would cross security boundary.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>  include/linux/mm.h | 7 +++++++
>  mm/ksm.c           | 3 +++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index ebf4bd8bd0bf..406a28cadfcf 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1548,6 +1548,13 @@ static inline int vma_keyid(struct vm_area_struct *vma)
>  }
>  #endif
>  
> +#ifndef page_keyid
> +static inline int page_keyid(struct page *page)
> +{
> +	return 0;
> +}
> +#endif
> +
>  #ifdef CONFIG_SHMEM
>  /*
>   * The vma_is_shmem is not inline because it is used only by slow
> diff --git a/mm/ksm.c b/mm/ksm.c
> index a6d43cf9a982..1bd7b9710e29 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -1214,6 +1214,9 @@ static int try_to_merge_one_page(struct vm_area_struct *vma,
>  	if (!PageAnon(page))
>  		goto out;
>  
> +	if (page_keyid(page) != page_keyid(kpage))
> +		goto out;
> +
>  	/*
>  	 * We need the page lock to read a stable PageSwapCache in
>  	 * write_protect_page().  We use trylock_page() instead of
> -- 
> 2.18.0
>