Messages in this thread |  | | Subject | Re: [PATCH] staging: comedi: drivers: Fix memory leak in gsc_hpdi_auto_attach | From | Ian Abbott <> | Date | Mon, 16 Dec 2019 10:36:28 +0000 |
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On 15/12/2019 01:33, Navid Emamdoost wrote: > In the implementation of gsc_hpdi_auto_attach(), the allocated dma > description is leaks in case of alignment error, or failure of > gsc_hpdi_setup_dma_descriptors() or comedi_alloc_subdevices(). Release > devpriv->dma_desc via dma_free_coherent(). > > Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Actually, there is no memory leak (although there is another problem that I'll mention below). If the "auto_attach" handler gsc_hpdi_auto_attach() returns an error, then the "detach" handler gsc_hpdi_detach() will be called automatically to clean up. (This is true for all comedi drivers). gsc_hpdi_detach() calls gsc_hpdi_free_dma() to free the DMA buffers and DMA descriptors.
> --- > drivers/staging/comedi/drivers/gsc_hpdi.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > > diff --git a/drivers/staging/comedi/drivers/gsc_hpdi.c b/drivers/staging/comedi/drivers/gsc_hpdi.c > index 4bdf44d82879..c0c7047a6d1b 100644 > --- a/drivers/staging/comedi/drivers/gsc_hpdi.c > +++ b/drivers/staging/comedi/drivers/gsc_hpdi.c > @@ -633,16 +633,17 @@ static int gsc_hpdi_auto_attach(struct comedi_device *dev, > if (devpriv->dma_desc_phys_addr & 0xf) { > dev_warn(dev->class_dev, > " dma descriptors not quad-word aligned (bug)\n"); > - return -EIO; > + retval = -EIO; > + goto release_dma_desc; > } > > retval = gsc_hpdi_setup_dma_descriptors(dev, 0x1000); > if (retval < 0) > - return retval; > + goto release_dma_desc; > > retval = comedi_alloc_subdevices(dev, 1); > if (retval) > - return retval; > + goto release_dma_desc; > > /* Digital I/O subdevice */ > s = &dev->subdevices[0]; > @@ -660,6 +661,15 @@ static int gsc_hpdi_auto_attach(struct comedi_device *dev, > s->cancel = gsc_hpdi_cancel; > > return gsc_hpdi_init(dev); > + > +release_dma_desc: > + if (devpriv->dma_desc) > + dma_free_coherent(&pcidev->dev, > + sizeof(struct plx_dma_desc) * > + NUM_DMA_DESCRIPTORS, > + devpriv->dma_desc, > + devpriv->dma_desc_phys_addr); > + return retval; > } > > static void gsc_hpdi_detach(struct comedi_device *dev) >
This patch could actually result in devpriv->dma_desc being freed twice - once in the 'release_dma_desc:' code and again when gsc_hpdi_detach() is called externally as part of the clean-up.
The real bug in the original code is that it does not check whether any of the calls to dma_alloc_coherent() returned NULL. If any of the calls to dma_alloc_coherent() returns NULL, gsc_hpdi_auto_attach() needs to return an error (-ENOMEM). The subsequent call to gsc_hpdi_detach() will then free whatever DMA coherent buffers where allocated.
-- -=( Ian Abbott <abbotti@mev.co.uk> || Web: www.mev.co.uk )=- -=( MEV Ltd. is a company registered in England & Wales. )=- -=( Registered number: 02862268. Registered address: )=- -=( 15 West Park Road, Bramhall, STOCKPORT, SK7 3JZ, UK. )=-
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