blob: 6288267b2e89b20be8b84ce8b7bc0befca07024b [file] [log] [blame]
From 80f44dc05cc312060b5755d69b4bf30d8dbccb13 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@amd.com>
Date: Thu, 1 Aug 2019 15:11:14 +0200
Subject: [PATCH] dma-buf: fix stack corruption in dma_fence_chain_release
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commit 92cb3e5980638a37c56091e605aa837d0af05a9d upstream.
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 K├Ânig <christian.koenig@amd.com>
Acked-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: 7bf60c52e093 ("dma-buf: add new dma_fence_chain container v7")
Link: https://patchwork.freedesktop.org/patch/321612/
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
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);
}
--
2.27.0