linux-kernel - Re: [PATCH v36 10/24] mm: Add vm

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Date:   Thu, 06 Aug 2020 14:35:17 +0100
From:   Darren Kenny <darren.kenny@...cle.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>, x86@...nel.org,
        linux-sgx@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jethro Beekman <jethro@...tanix.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        andriy.shevchenko@...ux.intel.com, asapek@...gle.com, bp@...en8.de,
        cedric.xing@...el.com, chenalexchen@...gle.com,
        conradparker@...gle.com, cyhanish@...gle.com,
        dave.hansen@...el.com, haitao.huang@...el.com,
        josh@...htriplett.org, kai.huang@...el.com, kai.svahn@...el.com,
        kmoy@...gle.com, ludloff@...gle.com, luto@...nel.org,
        nhorman@...hat.com, npmccallum@...hat.com, puiterwijk@...hat.com,
        rientjes@...gle.com, tglx@...utronix.de, yaozhangx@...gle.com
Subject: Re: [PATCH v36 10/24] mm: Add vm_ops->mprotect()

On Thursday, 2020-07-16 at 16:52:49 +03, Jarkko Sakkinen wrote:
> From: Sean Christopherson <sean.j.christopherson@...el.com>
>
> Add vm_ops()->mprotect() for additional constraints for a VMA.
>
> Intel Software Guard eXtensions (SGX) will use this callback to add two
> constraints:
>
> 1. Verify that the address range does not have holes: each page address
>    must be filled with an enclave page.
> 2. Verify that VMA permissions won't surpass the permissions of any enclave
>    page within the address range. Enclave cryptographically sealed
>    permissions for each page address that set the upper limit for possible
>    VMA permissions. Not respecting this can cause #GP's to be emitted.
>
> Cc: linux-mm@...ck.org
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Matthew Wilcox <willy@...radead.org>
> Acked-by: Jethro Beekman <jethro@...tanix.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Co-developed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

Reviewed-by: Darren Kenny <darren.kenny@...cle.com>

> ---
>  include/linux/mm.h | 3 +++
>  mm/mprotect.c      | 5 ++++-
>  2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index dc7b87310c10..458e8cb99aaf 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -542,6 +542,9 @@ struct vm_operations_struct {
>  	void (*close)(struct vm_area_struct * area);
>  	int (*split)(struct vm_area_struct * area, unsigned long addr);
>  	int (*mremap)(struct vm_area_struct * area);
> +	int (*mprotect)(struct vm_area_struct *vma,
> +			struct vm_area_struct **pprev, unsigned long start,
> +			unsigned long end, unsigned long newflags);
>  	vm_fault_t (*fault)(struct vm_fault *vmf);
>  	vm_fault_t (*huge_fault)(struct vm_fault *vmf,
>  			enum page_entry_size pe_size);
> diff --git a/mm/mprotect.c b/mm/mprotect.c
> index ce8b8a5eacbb..f170f3da8a4f 100644
> --- a/mm/mprotect.c
> +++ b/mm/mprotect.c
> @@ -610,7 +610,10 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
>  		tmp = vma->vm_end;
>  		if (tmp > end)
>  			tmp = end;
> -		error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
> +		if (vma->vm_ops && vma->vm_ops->mprotect)
> +			error = vma->vm_ops->mprotect(vma, &prev, nstart, tmp, newflags);
> +		else
> +			error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
>  		if (error)
>  			goto out;
>  		nstart = tmp;
> -- 
> 2.25.1