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@xxxxxxx> > Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx> > --- > 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);
