linux-stable/drivers/dma-buf/Kconfig
Daniel Vetter 84335675f2 dma-buf: Add debug option
We have too many people abusing the struct page they can get at but
really shouldn't in importers. Aside from that the backing page might
simply not exist (for dynamic p2p mappings) looking at it and using it
e.g. for mmap can also wreak the page handling of the exporter
completely. Importers really must go through the proper interface like
dma_buf_mmap for everything.

I'm semi-tempted to enforce this for dynamic importers since those
really have no excuse at all to break the rules.

Unfortuantely we can't store the right pointers somewhere safe to make
sure we oops on something recognizable, so best is to just wrangle
them a bit by flipping all the bits. At least on x86 kernel addresses
have all their high bits sets and the struct page array is fairly low
in the kernel mapping, so flipping all the bits gives us a very high
pointer in userspace and hence excellent chances for an invalid
dereference.

v2: Add a note to the @map_dma_buf hook that exporters shouldn't do
fancy caching tricks, which would blow up with this address scrambling
trick here (Chris)

Enable by default when CONFIG_DMA_API_DEBUG is enabled.

v3: Only one copy of the mangle/unmangle code (Christian)

v4: #ifdef, not #if (0day)

v5: sg_table can also be an ERR_PTR (Chris, Christian)

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Stevens <stevensd@chromium.org>
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Link: https://patchwork.freedesktop.org/patch/msgid/20210115164739.3958206-1-daniel.vetter@ffwll.ch
2021-01-18 14:26:51 +01:00

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# SPDX-License-Identifier: GPL-2.0-only
menu "DMABUF options"
config SYNC_FILE
bool "Explicit Synchronization Framework"
default n
select DMA_SHARED_BUFFER
help
The Sync File Framework adds explicit synchronization via
userspace. It enables send/receive 'struct dma_fence' objects to/from
userspace via Sync File fds for synchronization between drivers via
userspace components. It has been ported from Android.
The first and main user for this is graphics in which a fence is
associated with a buffer. When a job is submitted to the GPU a fence
is attached to the buffer and is transferred via userspace, using Sync
Files fds, to the DRM driver for example. More details at
Documentation/driver-api/sync_file.rst.
config SW_SYNC
bool "Sync File Validation Framework"
default n
depends on SYNC_FILE
depends on DEBUG_FS
help
A sync object driver that uses a 32bit counter to coordinate
synchronization. Useful when there is no hardware primitive backing
the synchronization.
WARNING: improper use of this can result in deadlocking kernel
drivers from userspace. Intended for test and debug only.
config UDMABUF
bool "userspace dmabuf misc driver"
default n
depends on DMA_SHARED_BUFFER
depends on MEMFD_CREATE || COMPILE_TEST
help
A driver to let userspace turn memfd regions into dma-bufs.
Qemu can use this to create host dmabufs for guest framebuffers.
config DMABUF_MOVE_NOTIFY
bool "Move notify between drivers (EXPERIMENTAL)"
default n
help
Don't pin buffers if the dynamic DMA-buf interface is available on
both the exporter as well as the importer. This fixes a security
problem where userspace is able to pin unrestricted amounts of memory
through DMA-buf.
This is marked experimental because we don't yet have a consistent
execution context and memory management between drivers.
config DMABUF_DEBUG
bool "DMA-BUF debug checks"
default y if DMA_API_DEBUG
help
This option enables additional checks for DMA-BUF importers and
exporters. Specifically it validates that importers do not peek at the
underlying struct page when they import a buffer.
config DMABUF_SELFTESTS
tristate "Selftests for the dma-buf interfaces"
default n
depends on DMA_SHARED_BUFFER
menuconfig DMABUF_HEAPS
bool "DMA-BUF Userland Memory Heaps"
select DMA_SHARED_BUFFER
help
Choose this option to enable the DMA-BUF userland memory heaps.
This options creates per heap chardevs in /dev/dma_heap/ which
allows userspace to allocate dma-bufs that can be shared
between drivers.
source "drivers/dma-buf/heaps/Kconfig"
endmenu