From 92cb3e5980638a37c56091e605aa837d0af05a9d Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Christian=20K=C3=B6nig?= Date: Thu, 1 Aug 2019 15:11:14 +0200 Subject: [PATCH] dma-buf: fix stack corruption in dma_fence_chain_release MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We can't free up the chain using recursion or we run into a stack overflow. Manually free up the dangling chain nodes to avoid recursion. Signed-off-by: Christian König Acked-by: Lionel Landwerlin Fixes: 7bf60c52e093 ("dma-buf: add new dma_fence_chain container v7") Link: https://patchwork.freedesktop.org/patch/321612/ --- drivers/dma-buf/dma-fence-chain.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/drivers/dma-buf/dma-fence-chain.c b/drivers/dma-buf/dma-fence-chain.c index b5089f64be2a..44a741677d25 100644 --- a/drivers/dma-buf/dma-fence-chain.c +++ b/drivers/dma-buf/dma-fence-chain.c @@ -178,8 +178,30 @@ static bool dma_fence_chain_signaled(struct dma_fence *fence) static void dma_fence_chain_release(struct dma_fence *fence) { struct dma_fence_chain *chain = to_dma_fence_chain(fence); + struct dma_fence *prev; + + /* Manually unlink the chain as much as possible to avoid recursion + * and potential stack overflow. + */ + while ((prev = rcu_dereference_protected(chain->prev, true))) { + struct dma_fence_chain *prev_chain; + + if (kref_read(&prev->refcount) > 1) + break; + + prev_chain = to_dma_fence_chain(prev); + if (!prev_chain) + break; + + /* No need for atomic operations since we hold the last + * reference to prev_chain. + */ + chain->prev = prev_chain->prev; + RCU_INIT_POINTER(prev_chain->prev, NULL); + dma_fence_put(prev); + } + dma_fence_put(prev); - dma_fence_put(rcu_dereference_protected(chain->prev, true)); dma_fence_put(chain->fence); dma_fence_free(fence); }