Messages in this thread | | | Subject | Re: [PATCH] dma: Fix a double free in dma_async_device_register | From | Dave Jiang <> | Date | Tue, 30 Mar 2021 09:05:15 -0700 |
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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.
> > Fixes: d2fb0a0438384 ("dmaengine: break out channel registration") > Signed-off-by: Lv Yunlong <lyl2019@mail.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);
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