linux-kernel - [PATCH] dma: Fix a double free in dma_async_device

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Date:   Tue, 30 Mar 2021 02:01:49 -0700
From:   Lv Yunlong <lyl2019@...l.ustc.edu.cn>
To:     vkoul@...nel.org, dave.jiang@...el.com
Cc:     dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lv Yunlong <lyl2019@...l.ustc.edu.cn>
Subject: [PATCH] dma: Fix a double free in dma_async_device_register

In the first list_for_each_entry() macro of dma_async_device_register,
it gets the chan from list and calls __dma_async_device_channel_register
(..,chan). We can see that chan->local is allocated by alloc_percpu() and
it is freed chan->local by free_percpu(chan->local) when
__dma_async_device_channel_register() failed.

But after __dma_async_device_channel_register() failed, the caller will
goto err_out and freed the chan->local in the second time by free_percpu().

The cause of this problem is forget to set chan->local to NULL when
chan->local was freed in __dma_async_device_channel_register(). My
patch sets chan->local to NULL when the callee failed to avoid double free.

Fixes: d2fb0a0438384 ("dmaengine: break out channel registration")
Signed-off-by: Lv Yunlong <lyl2019@...l.ustc.edu.cn>
---
 drivers/dma/dmaengine.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index fe6a460c4373..fef64b198c95 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -1249,8 +1249,10 @@ int dma_async_device_register(struct dma_device *device)
 	/* represent channels in sysfs. Probably want devs too */
 	list_for_each_entry(chan, &device->channels, device_node) {
 		rc = __dma_async_device_channel_register(device, chan);
-		if (rc < 0)
+		if (rc < 0) {
+			chan->local = NULL;
 			goto err_out;
+		}
 	}

 	mutex_lock(&dma_list_mutex);
-- 
2.25.1