linux-kernel - [PATCH V2] dma-mapping: Set dma_mem pointer as NULL after it's freed

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Message-Id: <20231214082526.1212264-1-joakim.zhang@cixtech.com>
Date:   Thu, 14 Dec 2023 16:25:26 +0800
From:   joakim.zhang@...tech.com
To:     hch@....de, m.szyprowski@...sung.com, robin.murphy@....com
Cc:     iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
        cix-kernel-upstream@...tech.com,
        Joakim Zhang <joakim.zhang@...tech.com>
Subject: [PATCH V2] dma-mapping: Set dma_mem pointer as NULL after it's freed

From: Joakim Zhang <joakim.zhang@...tech.com>

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@...tech.com>
---
ChangeLogs:
V1->V2:
	* remove _dma_release_coherent_memory() from
	rmem_dma_device_release()
	* update commit message
---
 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 c21abc77c53e..ff5683a57f77 100644
--- a/kernel/dma/coherent.c
+++ b/kernel/dma/coherent.c
@@ -132,8 +132,10 @@ int dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr,
 
 void dma_release_coherent_memory(struct device *dev)
 {
-	if (dev)
+	if (dev) {
 		_dma_release_coherent_memory(dev->dma_mem);
+		dev->dma_mem = NULL;
+	}
 }
 
 static void *__dma_alloc_from_coherent(struct device *dev,
-- 
2.25.1