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SubjectRe: [PATCH v40 10/24] mm: Add 'mprotect' hook to struct vm_operations_struct
On Wed, Nov 04, 2020 at 04:54:16PM +0200, Jarkko Sakkinen wrote:
> From: Sean Christopherson <sean.j.christopherson@intel.com>
>
> Background
> ==========
>
> 1. SGX enclave pages are populated with data by copying from normal memory
> via ioctl() (SGX_IOC_ENCLAVE_ADD_PAGES), which will be added later in
> this series.
> 2. It is desirable to be able to restrict those normal memory data sources.
> For instance, to ensure that the source data is executable before
> copying data to an executable enclave page.
> 3. Enclave page permissions are dynamic (just like normal permissions) and
> can be adjusted at runtime with mprotect().
>
> This creates a problem because the original data source may have long since
> vanished at the time when enclave page permissions are established (mmap()
> or mprotect()).
>
> The solution (elsewhere in this series) is to force enclaves creators to
> declare their paging permission *intent* up front to the ioctl(). This
> intent can me immediately compared to the source data’s mapping and
> rejected if necessary.
>
> The “intent” is also stashed off for later comparison with enclave
> PTEs. This ensures that any future mmap()/mprotect() operations
> performed by the enclave creator or done on behalf of the enclave
> can be compared with the earlier declared permissions.
>
> Problem
> =======
>
> There is an existing mmap() hook which allows SGX to perform this
> permission comparison at mmap() time. However, there is no corresponding
> ->mprotect() hook.
>
> Solution
> ========
>
> Add a vm_ops->mprotect() hook so that mprotect() operations which are
> inconsistent with any page's stashed intent can be rejected by the driver.
>
> 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>
> Reviewed-by: Darren Kenny <darren.kenny@oracle.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>
> ---
> include/linux/mm.h | 3 +++
> mm/mprotect.c | 5 ++++-
> 2 files changed, 7 insertions(+), 1 deletion(-)

This needs an ACK from an mm person.

--
Regards/Gruss,
Boris.

https://people.kernel.org/tglx/notes-about-netiquette

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