[Linaro-mm-sig] [PATCH v3] Add udmabuf misc device
daniel.vetter at ffwll.ch
Tue May 29 12:29:43 UTC 2018
On Tue, May 29, 2018 at 12:48 PM, Gerd Hoffmann <kraxel at redhat.com> wrote:
>> > > qemu test branch:
>> > > https://git.kraxel.org/cgit/qemu/log/?h=sirius/udmabuf
>> > > + if (!shmem_mapping(file_inode(ubuf->filp)->i_mapping))
>> > > + goto err_free_ubuf;
>> Can/should we test here that the memfd has a locked down size here?
> Makes sense. Suggested way to check that? unstatic memfd_get_seals()
> function (mm/shmem.c)? Or is there some better way?
> Also which seals should we require? Is F_SEAL_SHRINK enough?
Yes I think that's enough.
Hm ... I think we also need to prevent the F_SEAL_WRITE, because
there's no way to stop dma from tampering with the buffer once it's a
dma-buf. Otherwise evil userspace could create a memfd, F_SEAL_SHRINK
it, make a dma-buf out of it, F_SEAL_WRITE it, hand it to some
unsuspecting priviledged service and then pull it over the table with
a few dma-buf writes.
>> On that: Link to userspace patches/git tree using this would be nice.
> See above.
Ow, I was blind :-)
Software Engineer, Intel Corporation
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