linux-kernel - Re: [PATCH v3 1/2] x86: Don't let pgprot_modify() change the page encryption bit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <eb422a3d-9f0e-5101-ebb6-c16f90219c3c@amd.com>
Date:   Mon, 16 Mar 2020 14:43:40 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Thomas Hellström (VMware) 
        <thomas_os@...pmail.org>, x86@...nel.org,
        Christoph Hellwig <hch@...radead.org>
Cc:     linux-kernel@...r.kernel.org,
        Thomas Hellstrom <thellstrom@...are.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Christian König <christian.koenig@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH v3 1/2] x86: Don't let pgprot_modify() change the page
 encryption bit

On 3/4/20 5:45 AM, Thomas Hellström (VMware) wrote:
> From: Thomas Hellstrom <thellstrom@...are.com>
> 
> When SEV or SME is enabled and active, vm_get_page_prot() typically
> returns with the encryption bit set. This means that users of
> pgprot_modify(, vm_get_page_prot()) (mprotect_fixup, do_mmap) end up with
> a value of vma->vm_pg_prot that is not consistent with the intended
> protection of the PTEs. This is also important for fault handlers that
> rely on the VMA vm_page_prot to set the page protection. Fix this by
> not allowing pgprot_modify() to change the encryption bit, similar to
> how it's done for PAT bits.
> 
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Christoph Hellwig <hch@...radead.org>
> Cc: Christian König <christian.koenig@....com>
> Cc: Marek Szyprowski <m.szyprowski@...sung.com>
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Signed-off-by: Thomas Hellstrom <thellstrom@...are.com>
> Reviewed-by: Dave Hansen <dave.hansen@...ux.intel.com>

Acked-by: Tom Lendacky <thomas.lendacky@....com>

> ---
>  arch/x86/include/asm/pgtable.h       | 7 +++++--
>  arch/x86/include/asm/pgtable_types.h | 2 +-
>  2 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
> index d9925b10e326..c4615032c5ef 100644
> --- a/arch/x86/include/asm/pgtable.h
> +++ b/arch/x86/include/asm/pgtable.h
> @@ -627,12 +627,15 @@ static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
>  	return __pmd(val);
>  }
>  
> -/* mprotect needs to preserve PAT bits when updating vm_page_prot */
> +/*
> + * mprotect needs to preserve PAT and encryption bits when updating
> + * vm_page_prot
> + */
>  #define pgprot_modify pgprot_modify
>  static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
>  {
>  	pgprotval_t preservebits = pgprot_val(oldprot) & _PAGE_CHG_MASK;
> -	pgprotval_t addbits = pgprot_val(newprot);
> +	pgprotval_t addbits = pgprot_val(newprot) & ~_PAGE_CHG_MASK;
>  	return __pgprot(preservebits | addbits);
>  }
>  
> diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
> index 0239998d8cdc..65c2ecd730c5 100644
> --- a/arch/x86/include/asm/pgtable_types.h
> +++ b/arch/x86/include/asm/pgtable_types.h
> @@ -118,7 +118,7 @@
>   */
>  #define _PAGE_CHG_MASK	(PTE_PFN_MASK | _PAGE_PCD | _PAGE_PWT |		\
>  			 _PAGE_SPECIAL | _PAGE_ACCESSED | _PAGE_DIRTY |	\
> -			 _PAGE_SOFT_DIRTY | _PAGE_DEVMAP)
> +			 _PAGE_SOFT_DIRTY | _PAGE_DEVMAP | _PAGE_ENC)
>  #define _HPAGE_CHG_MASK (_PAGE_CHG_MASK | _PAGE_PSE)
>  
>  /*
>