Messages in this thread | | | From | Marin Mitov <> | Subject | Re: [BUG][PATCH]dma-coherent.c: error path bug | Date | Mon, 7 Jun 2010 07:43:19 +0300 |
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On Monday, June 07, 2010 07:27:49 am FUJITA Tomonori wrote: > On Mon, 7 Jun 2010 07:08:56 +0300 > Marin Mitov <mitov@issp.bas.bg> wrote: > > > On Monday, June 07, 2010 05:30:48 am FUJITA Tomonori wrote: > > > On Sun, 6 Jun 2010 13:53:04 +0300 > > > Marin Mitov <mitov@issp.bas.bg> wrote: > > > > > > > Hi all, > > > > > > > > The error path in dma_declare_coherent_memory() leaves > > > > the pointer dev->dma_mem non completely initialized. > > > > > > > > If allocation of dev->dma_mem succeeds, > > > > but allocation of dev->dma_mem->bitmap fails > > > > dev->dma_mem is freed, but left non NULL > > > > and non completely initialized. > > > > > > > > Either zero it after being freed (one liner patch), or assign to > > > > dev->dma_mem only completely initialized structure (patch included). > > > > > > > > Comments welcome. > > > > > > > > Marin Mitov > > > > > > > > Signed-off-by: Marin Mitov <mitov@issp.bas.bg> > > > > > > Hmm, if dma_declare_coherent_memory() fails, the driver doesn't use > > > dev->dma_mem. So even if dev->dma_mem points to a freed memory, I'm > > > not sure that it causes a real problem. We could call this patch a > > > cleanup though. > > > > > My understanding of dma_alloc_coherent() is that we first try to allocate from > > per-device coherent memory and we do it using dma_alloc_from_coherent() > > (in drivers/base/dma-coherent.c) if dev->dma_mem is not NULL (and we have > > left it not NULL, here is the problem). If allocation of dev->dma_mem->bitmap > > fails dev->dma_mem must be NULL. > > But are there any driver that can continue when dma_declare_coherent_memory() fails? > I do not know if such a real driver exists.
My understanding of drivers' use of dma_declare_coherent_memory() is to declare some (may be on board) memory as coherent, so when they call dma_alloc_coherent() the request is satisfied first from this area and when it is exhausted fall back to other pools of coherent memory. As far as a fall back exists the driver may continue even if dma_declare_coherent_memory() fails.
Marin Mitov
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