[PATCH v10 0/3] Secure Memory Allocation Framework

Wed Oct 5 13:40:14 UTC 2016

because with ion it is up to userland to decide which heap to use
and until now userland doesn't have any way to get device constraints...

I will prefer let a central allocator (in kernel) decide from the
attached devices
which allocator is the best. It is what I have implemented in smaf.

Benjamin

2016-10-05 15:19 GMT+02:00 Daniel Vetter <daniel at ffwll.ch>:
> On Tue, Oct 04, 2016 at 01:47:21PM +0200, Benjamin Gaignard wrote:
>> version 10 changes:
>>  - rebased on kernel 4.8 tag
>>  - minor typo fix
>>
>> version 9 changes:
>>  - rebased on 4.8-rc5
>>  - struct dma_attrs doesn't exist anymore so update CMA allocator
>>    to compile with new dma_*_attr functions
>>  - add example SMAF use case in cover letter
>>
>> version 8 changes:
>>  - rework of the structures used within ioctl
>>    by adding a version field and padding to be futur proof
>>  - rename fake secure moduel to test secure module
>>  - fix the various remarks done on the previous patcheset
>>
>> version 7 changes:
>>  - rebased on kernel 4.6-rc7
>>  - simplify secure module API
>>  - add vma ops to be able to detect mmap/munmap calls
>>  - add ioctl to get number and allocator names
>>  - update libsmaf with adding tests
>>    https://git.linaro.org/people/benjamin.gaignard/libsmaf.git
>>  - add debug log in fake secure module
>>
>> version 6 changes:
>>  - rebased on kernel 4.5-rc4
>>  - fix mmapping bug while requested allocation size isn't a a multiple of
>>    PAGE_SIZE (add a test for this in libsmaf)
>>
>> version 5 changes:
>>  - rebased on kernel 4.3-rc6
>>  - rework locking schema and make handle status use an atomic_t
>>  - add a fake secure module to allow performing tests without trusted
>>    environment
>>
>> version 4 changes:
>>  - rebased on kernel 4.3-rc3
>>  - fix missing EXPORT_SYMBOL for smaf_create_handle()
>>
>> version 3 changes:
>>  - Remove ioctl for allocator selection instead provide the name of
>>    the targeted allocator with allocation request.
>>    Selecting allocator from userland isn't the prefered way of working
>>    but is needed when the first user of the buffer is a software component.
>>  - Fix issues in case of error while creating smaf handle.
>>  - Fix module license.
>>  - Update libsmaf and tests to care of the SMAF API evolution
>>    https://git.linaro.org/people/benjamin.gaignard/libsmaf.git
>>
>> version 2 changes:
>>  - Add one ioctl to allow allocator selection from userspace.
>>    This is required for the uses case where the first user of
>>    the buffer is a software IP which can't perform dma_buf attachement.
>>  - Add name and ranking to allocator structure to be able to sort them.
>>  - Create a tiny library to test SMAF:
>>    https://git.linaro.org/people/benjamin.gaignard/libsmaf.git
>>  - Fix one issue when try to secure buffer without secure module registered
>>
>> SMAF aim to solve two problems: allocating memory that fit with hardware IPs
>> constraints and secure those data from bus point of view.
>>
>> One example of SMAF usage is camera preview: on SoC you may use either an USB
>> webcam or the built-in camera interface and the frames could be send directly
>> to the dipslay Ip or handle by GPU.
>> Most of USB interfaces and GPU have mmu but almost all built-in camera
>> interace and display Ips don't have mmu so when selecting how allocate
>> buffer you need to be aware of each devices constraints (contiguous memroy,
>> stride, boundary, alignment ...).
>> ION has solve this problem by let userland decide which allocator (heap) to use
>> but this require to adapt userland for each platform and sometime for each
>> use case.
>>
>> To be sure to select the best allocation method for devices SMAF implement
>> deferred allocation mechanism: memory allocation is only done when the first
>> device effectively required it.
>> Allocator modules have to implement a match() to let SMAF know if they are
>> compatibles with devices needs.
>> This patch set provide an example of allocator module which use
>> dma_{alloc/free/mmap}_attrs() and check if at least one device have
>> coherent_dma_mask set to DMA_BIT_MASK(32) in match function.
>>
>> In the same camera preview use case, SMAF allow to protect the data from being
>> read by unauthorized IPs (i.e. a malware to dump camera stream).
>> Until now I have only see access rights protection at process/thread level
>> (PKeys/MPK) or on file (SELinux) but nothing allow to drive data bus firewalls.
>> SMAF propose an interface to control and implement those firewalls.
>> Like IOMMU, firewalls IPs can help to protect memory from malicious/faulty devices
>> that are attempting DMA attacks.
>>
>> Secure modules are responsibles of granting and revoking devices access rights
>> on the memory. Secure module is also called to check if CPU map memory into
>> kernel and user address spaces.
>> An example of secure module implementation can be found here:
>> http://git.linaro.org/people/benjamin.gaignard/optee-sdp.git
>> This code isn't yet part of the patch set because it depends on generic TEE
>> which is still under discussion (https://lwn.net/Articles/644646/)
>>
>> For allocation part of SMAF code I get inspirated by Sumit Semwal work about
>> constraint aware allocator.
>
> semi-random review comment, and a bit late: Why not implement smaf as a
> new heap in ion? I think consensus is pretty much that we'll be stuck with
> ion forever, and I think it's better to have 1 central buffer allocater
> than lots of them ...
> -Daniel
>
>>
>> Benjamin Gaignard (3):
>>   create SMAF module
>>   SMAF: add CMA allocator
>>   SMAF: add test secure module
>>
>>  drivers/Kconfig                |   2 +
>>  drivers/Makefile               |   1 +
>>  drivers/smaf/Kconfig           |  17 +
>>  drivers/smaf/Makefile          |   3 +
>>  drivers/smaf/smaf-cma.c        | 186 ++++++++++
>>  drivers/smaf/smaf-core.c       | 818 +++++++++++++++++++++++++++++++++++++++++
>>  drivers/smaf/smaf-testsecure.c |  90 +++++
>>  include/linux/smaf-allocator.h |  45 +++
>>  include/linux/smaf-secure.h    |  65 ++++
>>  include/uapi/linux/smaf.h      |  85 +++++
>>  10 files changed, 1312 insertions(+)
>>  create mode 100644 drivers/smaf/Kconfig
>>  create mode 100644 drivers/smaf/Makefile
>>  create mode 100644 drivers/smaf/smaf-cma.c
>>  create mode 100644 drivers/smaf/smaf-core.c
>>  create mode 100644 drivers/smaf/smaf-testsecure.c
>>  create mode 100644 include/linux/smaf-allocator.h
>>  create mode 100644 include/linux/smaf-secure.h
>>  create mode 100644 include/uapi/linux/smaf.h
>>
>> --
>> 1.9.1
>>
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>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
Benjamin Gaignard

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