* [PATCH] staging: comedi: drivers: Fix memory leak in gsc_hpdi_auto_attach
@ 2019-12-15 1:33 Navid Emamdoost
2019-12-15 15:07 ` Markus Elfring
2019-12-16 10:36 ` Ian Abbott
0 siblings, 2 replies; 4+ messages in thread
From: Navid Emamdoost @ 2019-12-15 1:33 UTC (permalink / raw)
To: Ian Abbott, H Hartley Sweeten, Greg Kroah-Hartman,
Navid Emamdoost, devel, linux-kernel
Cc: emamd001
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>
---
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)
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] staging: comedi: drivers: Fix memory leak in gsc_hpdi_auto_attach
2019-12-15 1:33 [PATCH] staging: comedi: drivers: Fix memory leak in gsc_hpdi_auto_attach Navid Emamdoost
@ 2019-12-15 15:07 ` Markus Elfring
2019-12-16 10:36 ` Ian Abbott
1 sibling, 0 replies; 4+ messages in thread
From: Markus Elfring @ 2019-12-15 15:07 UTC (permalink / raw)
To: Navid Emamdoost, devel
Cc: linux-kernel, kernel-janitors, Greg Kroah-Hartman,
H Hartley Sweeten, Ian Abbott, Navid Emamdoost
> In the implementation of gsc_hpdi_auto_attach(), the allocated dma
> description is leaks in case of alignment error, …
Please avoid a typo in this change message.
…
+++ b/drivers/staging/comedi/drivers/gsc_hpdi.c
…
> @@ -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)
I got the impression that return values from calls of the function “dma_alloc_coherent”
should be checked before.
* Would you like to add null pointer checks at other source code places?
* Should the jump targets be accordingly adjusted then for the completion
of the desired exception handling?
Regards,
Markus
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] staging: comedi: drivers: Fix memory leak in gsc_hpdi_auto_attach
2019-12-15 1:33 [PATCH] staging: comedi: drivers: Fix memory leak in gsc_hpdi_auto_attach Navid Emamdoost
2019-12-15 15:07 ` Markus Elfring
@ 2019-12-16 10:36 ` Ian Abbott
2019-12-16 20:18 ` Navid Emamdoost
1 sibling, 1 reply; 4+ messages in thread
From: Ian Abbott @ 2019-12-16 10:36 UTC (permalink / raw)
To: Navid Emamdoost, H Hartley Sweeten, Greg Kroah-Hartman, devel,
linux-kernel
Cc: emamd001
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. )=-
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] staging: comedi: drivers: Fix memory leak in gsc_hpdi_auto_attach
2019-12-16 10:36 ` Ian Abbott
@ 2019-12-16 20:18 ` Navid Emamdoost
0 siblings, 0 replies; 4+ messages in thread
From: Navid Emamdoost @ 2019-12-16 20:18 UTC (permalink / raw)
To: Ian Abbott
Cc: H Hartley Sweeten, Greg Kroah-Hartman, devel, LKML, Navid Emamdoost
Ian, thanks for your feedback.
On Mon, Dec 16, 2019 at 4:36 AM Ian Abbott <abbotti@mev.co.uk> wrote:
>
> 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.
>
I was aware that comedi_alloc_devpriv() is a resource managed
allocation, but was not sure how subsequent dma_desc allocation will
be handled when device detach.
> > ---
> > 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.
>
Yes, this potential null deref is another type of bug, which I will
send a patch for separately.
> --
> -=( 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. )=-
--
Navid.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2019-12-15 1:33 [PATCH] staging: comedi: drivers: Fix memory leak in gsc_hpdi_auto_attach Navid Emamdoost
2019-12-15 15:07 ` Markus Elfring
2019-12-16 10:36 ` Ian Abbott
2019-12-16 20:18 ` Navid Emamdoost
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