drm/i915: Prevent writing into a read-only object via a GGTT mmap

If the user has created a read-only object, they should not be allowed
to circumvent the write protection by using a GGTT mmapping. Deny it.

Also most machines do not support read-only GGTT PTEs, so again we have
to reject attempted writes. Fortunately, this is known a priori, so we
can at least reject in the call to create the mmap (with a sanity check
in the fault handler).

v2: Check the vma->vm_flags during mmap() to allow readonly access.
v3: Remove VM_MAYWRITE to curtail mprotect()

Testcase: igt/gem_userptr_blits/readonly_mmap*
Signed-off-by: Chris Wilson <[email protected]>
Cc: Jon Bloomfield <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Matthew Auld <[email protected]>
Cc: David Herrmann <[email protected]>
Reviewed-by: Matthew Auld <[email protected]> #v1
Reviewed-by: Jon Bloomfield <[email protected]>
Reviewed-by: Joonas Lahtinen <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 6de88add508a..69bd7f697f6d 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1100,7 +1100,7 @@ intel_ring_create_vma(struct drm_i915_private *dev_priv, int size)
 	 * if supported by the platform's GGTT.
 	 */
 	if (vm->has_read_only)
-		obj->gt_ro = 1;
+		i915_gem_object_set_readonly(obj);
 
 	vma = i915_vma_instance(obj, vm, NULL);
 	if (IS_ERR(vma))