Re: [PATCH] dma: Fix a double free in dma_async_device_register
From: Dave Jiang <dave.jiang@intel.com>
Date: 2021-03-30 16:06:07
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On 3/30/2021 2:01 AM, 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.
Thanks for the fix. I think it would make sense to set it to NULL in __dma_async_device_channel_register() cleanup path after it calls free_percpu(chan->local) right? That would address any other instances of this issue happening else where.
quoted hunk ↗ jump to hunk
Fixes: d2fb0a0438384 ("dmaengine: break out channel registration") Signed-off-by: Lv Yunlong <redacted> --- 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);