[04/11] dma-buf: warn about dma_fence_array container rules v2
Commit Message
It's not allowed to nest another dma_fence container into a dma_fence_array
or otherwise we can run into recursion.
Warn about that when we create a dma_fence_array.
v2: fix comment style and typo in the warning pointed out by Thomas
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
drivers/dma-buf/dma-fence-array.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
Comments
On Mon, 2022-01-24 at 14:03 +0100, Christian König wrote:
> It's not allowed to nest another dma_fence container into a
> dma_fence_array
> or otherwise we can run into recursion.
>
> Warn about that when we create a dma_fence_array.
>
> v2: fix comment style and typo in the warning pointed out by Thomas
>
> Signed-off-by: Christian König <christian.koenig@amd.com>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
> drivers/dma-buf/dma-fence-array.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-
> fence-array.c
> index 3e07f961e2f3..cb1bacb5a42b 100644
> --- a/drivers/dma-buf/dma-fence-array.c
> +++ b/drivers/dma-buf/dma-fence-array.c
> @@ -176,6 +176,20 @@ struct dma_fence_array
> *dma_fence_array_create(int num_fences,
>
> array->base.error = PENDING_ERROR;
>
> + /*
> + * dma_fence_array objects should never contain any other
> fence
> + * containers or otherwise we run into recursion and
> potential kernel
> + * stack overflow on operations on the dma_fence_array.
> + *
> + * The correct way of handling this is to flatten out the
> array by the
> + * caller instead.
> + *
> + * Enforce this here by checking that we don't create a
> dma_fence_array
> + * with any container inside.
> + */
> + while (num_fences--)
> + WARN_ON(dma_fence_is_container(fences[num_fences]));
> +
> return array;
> }
> EXPORT_SYMBOL(dma_fence_array_create);
@@ -176,6 +176,20 @@ struct dma_fence_array *dma_fence_array_create(int num_fences,
array->base.error = PENDING_ERROR;
+ /*
+ * dma_fence_array objects should never contain any other fence
+ * containers or otherwise we run into recursion and potential kernel
+ * stack overflow on operations on the dma_fence_array.
+ *
+ * The correct way of handling this is to flatten out the array by the
+ * caller instead.
+ *
+ * Enforce this here by checking that we don't create a dma_fence_array
+ * with any container inside.
+ */
+ while (num_fences--)
+ WARN_ON(dma_fence_is_container(fences[num_fences]));
+
return array;
}
EXPORT_SYMBOL(dma_fence_array_create);