async_tx: fix dma_wait_for_async_tx

Fix dma_wait_for_async_tx to not loop forever in the case where a
dependency chain is longer than two entries.  This condition will not
happen with current in-kernel drivers, but fix it for future drivers.

Found-by: Saeed Bishara <saeed.bishara@gmail.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/crypto/async_tx/async_tx.c b/crypto/async_tx/async_tx.c
index 035007145e78..bc18cbb8ea79 100644
--- a/crypto/async_tx/async_tx.c
+++ b/crypto/async_tx/async_tx.c
@@ -80,6 +80,7 @@ dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx)
 {
         enum dma_status status;
         struct dma_async_tx_descriptor *iter;
+        struct dma_async_tx_descriptor *parent;
 
         if (!tx)
                 return DMA_SUCCESS;
@@ -87,8 +88,15 @@ dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx)
         /* poll through the dependency chain, return when tx is complete */
         do {
                 iter = tx;
-                while (iter->cookie == -EBUSY)
-                        iter = iter->parent;
+
+                /* find the root of the unsubmitted dependency chain */
+                while (iter->cookie == -EBUSY) {
+                        parent = iter->parent;
+                        if (parent && parent->cookie == -EBUSY)
+                                iter = iter->parent;
+                        else
+                                break;
+                }
 
                 status = dma_sync_wait(iter->chan, iter->cookie);
         } while (status == DMA_IN_PROGRESS || (iter != tx));