Messages in this thread | | | Date | Fri, 19 Feb 2016 14:06:00 +0000 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH 2/2] ARM: dma-mapping: fix alloc/free for coherent + CMA + gfp=0 |
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On Fri, Feb 19, 2016 at 09:12:04AM +0100, Rabin Vincent wrote: > Given a device which uses arm_coherent_dma_ops and on which > dev_get_cma_area(dev) returns non-NULL, the following usage of the DMA > API with gfp=0 results in a memory leak and memory corruption. > > p = dma_alloc_coherent(dev, sz, &dma, 0); > if (p) > dma_free_coherent(dev, sz, p, dma); > > The memory leak is because the alloc allocates using > __alloc_simple_buffer() but the free attempts > dma_release_from_contiguous(), which does not do free anything since the > page is not in the CMA area.
I'd really like to see a better solution to this problem: over the course of the years, I've seen a number of patches that rearrange the test order at allocation time because of some problem or the other.
What we need is a better way to ensure that we use the correct release functionality - having two independent set of tests where the order matters is really not very good.
Maybe someone can put some thought into this...
-- RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
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