Re: [PATCHv2 02/16] iommu/omap: omap_iommu_attach() should return ENODEV, not NULL

[Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org>]

Hi Suman,

On Tuesday 25 February 2014 16:32:03 Suman Anna wrote:
> On 02/25/2014 03:13 PM, Laurent Pinchart wrote:
> > On Thursday 13 February 2014 12:15:33 Suman Anna wrote:
> >> From: Florian Vaussard <florian.vaussard-p8DiymsW2f8@public.gmane.org>
> >> 
> >> omap_iommu_attach() returns NULL or ERR_PTR in case of error, but
> >> omap_iommu_attach_dev() only checks for IS_ERR. Thus a NULL return value
> >> (in case driver_find_device fails) will cause the kernel to panic when
> >> omap_iommu_attach_dev() dereferences the pointer.
> >> 
> >> In such case, omap_iommu_attach() should return ENODEV, not NULL.
> >> 
> >> Signed-off-by: Florian Vaussard <florian.vaussard-p8DiymsW2f8@public.gmane.org>
> >> Acked-by: Suman Anna <s-anna-l0cyMroinI0@public.gmane.org>
> >> ---
> >> 
> >>   drivers/iommu/omap-iommu.c | 4 ++--
> >>   1 file changed, 2 insertions(+), 2 deletions(-)
> >> 
> >> diff --git a/drivers/iommu/omap-iommu.c b/drivers/iommu/omap-iommu.c
> >> index fff2ffd..6272c36 100644
> >> --- a/drivers/iommu/omap-iommu.c
> >> +++ b/drivers/iommu/omap-iommu.c
> >> @@ -863,7 +863,7 @@ static int device_match_by_alias(struct device *dev,
> >> void *data) **/
> >> 
> >>   static struct omap_iommu *omap_iommu_attach(const char *name, u32
> >>   *iopgd)
> >>   {
> >> -	int err = -ENOMEM;
> >> +	int err = -ENODEV;
> >>   	struct device *dev;
> >>   	struct omap_iommu *obj;
> >> 
> >> @@ -871,7 +871,7 @@ static struct omap_iommu *omap_iommu_attach(const
> >> char *name, u32 *iopgd)
> >>   				(void *)name,
> >>   				device_match_by_alias);
> >>   	if (!dev)
> >> -		return NULL;
> >> +		return ERR_PTR(err);
> > 
> > I would return ERR_PTR(-ENODEV) here, and remove the initialization at
> > declaration of err above.
> 
> The initialization at the beginning is also serving one another exit
> path (a check for try_module_get), where err is not being set. If the
> initialization is removed, then the err has to be set explicitly at the
> other place. Let me know if you still want this changed.

The return value of iommu_enable() is unconditionally stored in err before the 
try_module_get() call, so that code patch is buggy anyway and should be fixed. 
I would still remove the initialization at declaration and assign -ENODEV to 
err explicitly when try_module_get() fails before the goto err_module.

> >>   	obj = to_iommu(dev);

-- 
Regards,

Laurent Pinchart