linux-kernel - Re: [PATCH v2] dma: Fix a double free in dma_async_device

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Message-ID: <756f1b55-5ab8-157c-95c7-a071c572248e@intel.com>
Date:   Tue, 30 Mar 2021 19:48:33 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Lv Yunlong <lyl2019@...l.ustc.edu.cn>, vkoul@...nel.org
Cc:     dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] dma: Fix a double free in dma_async_device_register


On 3/30/2021 6:44 PM, Lv Yunlong wrote:
> 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>

Reviewed-by: Dave Jiang <dave.jiang@...el.com>


> ---
>   drivers/dma/dmaengine.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
> index fe6a460c4373..af3ee288bc11 100644
> --- a/drivers/dma/dmaengine.c
> +++ b/drivers/dma/dmaengine.c
> @@ -1086,6 +1086,7 @@ static int __dma_async_device_channel_register(struct dma_device *device,
>   	kfree(chan->dev);
>    err_free_local:
>   	free_percpu(chan->local);
> +	chan->local = NULL;
>   	return rc;
>   }
>