[PATCH 4.19 073/148] dma-mapping: clear dev->dma_mem to NULL after freeing it

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4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joakim Zhang <joakim.zhang@xxxxxxxxxxx>

[ Upstream commit b07bc2347672cc8c7293c64499f1488278c5ca3d ]

Reproduced with below sequence:
dma_declare_coherent_memory()->dma_release_coherent_memory()
->dma_declare_coherent_memory()->"return -EBUSY" error

It will return -EBUSY from the dma_assign_coherent_memory()
in dma_declare_coherent_memory(), the reason is that dev->dma_mem
pointer has not been set to NULL after it's freed.

Fixes: cf65a0f6f6ff ("dma-mapping: move all DMA mapping code to kernel/dma")
Signed-off-by: Joakim Zhang <joakim.zhang@xxxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 kernel/dma/coherent.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/dma/coherent.c b/kernel/dma/coherent.c
index 597d40893862..4c7ffd094a57 100644
--- a/kernel/dma/coherent.c
+++ b/kernel/dma/coherent.c
@@ -369,8 +369,10 @@ static int rmem_dma_device_init(struct reserved_mem *rmem, struct device *dev)
 static void rmem_dma_device_release(struct reserved_mem *rmem,
 				    struct device *dev)
 {
-	if (dev)
+	if (dev) {
 		dev->dma_mem = NULL;
+		dev->dma_mem = NULL;
+	}
 }
 
 static const struct reserved_mem_ops rmem_dma_ops = {
-- 
2.43.0







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