[Linaro-mm-sig] Re: [PATCH 2/4] dma-buf: warn about dma_fence_array container rules

On Wed, Jan 19, 2022 at 02:43:37PM +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.

Signed-off-by: Christian König christian.koenig@amd.com

drivers/dma-buf/dma-fence-array.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)

diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c index 3e07f961e2f3..4bfbcb885bbc 100644 --- a/drivers/dma-buf/dma-fence-array.c +++ b/drivers/dma-buf/dma-fence-array.c @@ -176,6 +176,19 @@ 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 (seqno--)

• WARN_ON(dma_fence_is_container(fences[seqno]));
  

Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch

• return array;

} EXPORT_SYMBOL(dma_fence_array_create); -- 2.25.1