[Intel-gfx] [PATCH] drm/i915: Relax mmap VMA check

[Chris Wilson]

Quoting Tvrtko Ursulin (2019-03-05 11:04:08)
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> Legacy behaviour was to allow non-page-aligned mmap requests, as does the
> linux mmap(2) implementation by virtue of automatically rounding up for
> the caller.
> 
> To avoid breaking legacy userspace relax the newly introduced fix.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Fixes: 5c4604e757ba ("drm/i915: Prevent a race during I915_GEM_MMAP ioctl with WC set")
> Reported-by: Guenter Roeck <linux at roeck-us.net>
> Cc: Adam Zabrocki <adamza at microsoft.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: <stable at vger.kernel.org> # v4.0+
> Cc: Akash Goel <akash.goel at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: intel-gfx at lists.freedesktop.org
> ---
>  drivers/gpu/drm/i915/i915_gem.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index a1ad5e137a97..0196ad97adcb 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1593,7 +1593,8 @@ __vma_matches(struct vm_area_struct *vma, struct file *filp,
>         if (vma->vm_file != filp)
>                 return false;
>  
> -       return vma->vm_start == addr && (vma->vm_end - vma->vm_start) == size;
> +       return vma->vm_start == addr &&
> +              (vma->vm_end - vma->vm_start) == PAGE_ALIGN(size);

Gosh and darnation,
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris