drm/i915: Relax mmap VMA check

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 <[email protected]>
Fixes: 5c4604e ("drm/i915: Prevent a race during I915_GEM_MMAP ioctl with WC set")
Reported-by: Guenter Roeck <[email protected]>
Cc: Adam Zabrocki <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: <[email protected]> # v4.0+
Cc: Akash Goel <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: [email protected]
Reviewed-by: Chris Wilson <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit a90e194)
Signed-off-by: Rodrigo Vivi <[email protected]>

drivers/gpu/drm/i915/i915_gem.c

@@ -1688,7 +1688,8 @@ __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);
 }
 
 /**