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If we have framebuffers that are >= 4GiB in size we will overflow the fb size check in intel_fill_fb_info(). Currently that is only possible with NV12 and CCS as offsets[1] may be anything between 0 and 0xffffffff. offsets[0] is currently required to be 0 so we can't hit the overflow with any single plane format (thanks to max fb size of 8kx8k and max stride of 32 KiB). In the future we may allow almost any framebuffer to exceed 4GiB in size so we really should fix the overflow. Not that the overflow is particularly dangerous. It's mostly just a sanity check against insane userspace. The display engine can't write to memory anyway so I suppose in the worst case we might anger the hw by attempting scanout past the end of the ggtt, or we might scan out some data that we're not supposed to see from other parts of the ggtt. Note that triggering this overflow depends on the driver aligning the fb height to the next tile boundary to push the calculated size above 4GiB. With linear buffers the effective tile height is one so that never happens, and the core already has a check for 32bit overflow of offsets[]+pitches[]*height. v2: Drop the unnecessary cast (Chris) Testcase: igt/kms_big_fb/x-tiled-addfb-size-offset-overflow Testcase: igt/kms_big_fb/y-tiled-addfb-size-offset-overflow Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Link: https://patchwork.freedesktop.org/patch/msgid/20180912180443.28649-1-ville.syrjala@linux.intel.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.