[PATCH] drivers: dma-coherent: free memory when failed to init DMA memory pool

[Michal Nazarewicz]

On Thu, Dec 03 2015, Duan Andy wrote:
> From: Mike Nazarewicz <mpn at google.com> Sent: Thursday, December 03, 2015 8:51 PM
>> To: Duan Fugang-B38611; torvalds at linux-foundation.org;
>> gregkh at linuxfoundation.org; m.szyprowski at samsung.com
>> Cc: linux-arm-kernel at lists.infradead.org; arnd at arndb.de;
>> iamjoonsoo.kim at lge.com; Duan Fugang-B38611
>> Subject: Re: [PATCH] drivers: dma-coherent: free memory when failed to
>> init DMA memory pool
>> 
>> On Thu, Dec 03 2015, Fugang Duan wrote:
>> > Free dma coherent memory when it failed to init DMA memory pool after
>> > calling .dma_init_coherent_memory(), otherwise it causes memmory leak.
>> >
>> > Signed-off-by: Fugang Duan <B38611 at freescale.com>
>> > ---
>> >  drivers/base/dma-coherent.c | 1 +
>> >  1 file changed, 1 insertion(+)
>> >
>> > diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
>> > index 55b8398..beb6bbe 100644
>> > --- a/drivers/base/dma-coherent.c
>> > +++ b/drivers/base/dma-coherent.c
>> > @@ -286,6 +286,7 @@ static int rmem_dma_device_init(struct reserved_mem
>> *rmem, struct device *dev)
>> >  				     &mem) != DMA_MEMORY_MAP) {
>> >  		pr_err("Reserved memory: failed to init DMA memory pool
>> at %pa, size %ld MiB\n",
>> >  			&rmem->base, (unsigned long)rmem->size / SZ_1M);
>> > +		kfree(mem);
>> 
>> mem == NULL at this point.  If dma_init_coherent_memory doesn’t return
>> DMA_MEMORY_MAP, mem pointer is not assigned any value.  If you think
>> there is a memory leak, please demonstrate a path of it happening.

> Kfree() will check mem NULL condition, so no need to add check in
> here.

Sure, but besides the point.  mem is always NULL so kfree(mem) is
a no-op so why add it?  There is no memory leak possible.  What is this
patch fixing?

>> >  		return -ENODEV;
>> >  	}
>> >  	rmem->priv = mem;

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