Re: [PATCH v36 10/24] mm: Add vm_ops->mprotect()

From: Darren Kenny <darren.kenny@oracle.com>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	x86@kernel.org, linux-sgx@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Matthew Wilcox <willy@infradead.org>,
	Jethro Beekman <jethro@fortanix.com>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	andriy.shevchenko@linux.intel.com, asapek@google.com,
	bp@alien8.de, cedric.xing@intel.com, chenalexchen@google.com,
	conradparker@google.com, cyhanish@google.com,
	dave.hansen@intel.com, haitao.huang@intel.com,
	josh@joshtriplett.org, kai.huang@intel.com, kai.svahn@intel.com,
	kmoy@google.com, ludloff@google.com, luto@kernel.org,
	nhorman@redhat.com, npmccallum@redhat.com, puiterwijk@redhat.com,
	rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com
Subject: Re: [PATCH v36 10/24] mm: Add vm_ops->mprotect()
Date: Thu, 06 Aug 2020 14:35:17 +0100	[thread overview]
Message-ID: <m2mu37rj6y.fsf@oracle.com> (raw)
In-Reply-To: <20200716135303.276442-11-jarkko.sakkinen@linux.intel.com>

On Thursday, 2020-07-16 at 16:52:49 +03, Jarkko Sakkinen wrote:
> From: Sean Christopherson <sean.j.christopherson@intel.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@kvack.org
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Matthew Wilcox <willy@infradead.org>
> Acked-by: Jethro Beekman <jethro@fortanix.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Co-developed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

Reviewed-by: Darren Kenny <darren.kenny@oracle.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