linux-kernel - Re: [PATCH Trivial] intel-iommu: check return value of device_to

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Message-ID: <CABawtvO5jOOanD_5Bzt6ebNOJaMUTvKNs8V9wah5QW_mBC1EFA@mail.gmail.com>
Date:	Fri, 10 Jan 2014 10:16:30 +0800
From:	Ethan Zhao <ethan.kernel@...il.com>
To:	Joerg Roedel <joro@...tes.org>
Cc:	ethan zhao <ethan.zhao@...cle.com>, dwmw2@...radead.org,
	Yinghai Lu <yinghai@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>, jiang.liu@...ux.intel.com,
	iommu@...ts.linux-foundation.org,
	linux-pci <linux-pci@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH Trivial] intel-iommu: check return value of
 device_to_iommu() before using it

On Thu, Jan 9, 2014 at 8:01 PM, Joerg Roedel <joro@...tes.org> wrote:
> On Thu, Jan 09, 2014 at 09:58:42AM +0800, ethan zhao wrote:
>>  drivers/iommu/intel-iommu.c |    2 ++
>>  1 files changed, 2 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
>> index 40203ad..5b4531a 100644
>> --- a/drivers/iommu/intel-iommu.c
>> +++ b/drivers/iommu/intel-iommu.c
>> @@ -1105,6 +1105,8 @@ static struct device_domain_info
>> *iommu_support_dev_iotlb(
>>      struct device_domain_info *info;
>>      struct intel_iommu *iommu = device_to_iommu(segment, bus, devfn);
>>
>> +    if (!iommu)
>> +        return NULL;
>>      if (!ecap_dev_iotlb_support(iommu->ecap))
>>          return NULL;
>
> This call can not fail, iommu_support_dev_iotlb() is only called from
> domain_context_mapping_one() which does the iommu==NULL check on its
> own before the call.
>
Agree, till now, was checked in domain_context_mapping_one(), but how
about if we query information with iommu_support_dev_iotlb() in other
code ?

Thanks,
Ethan
>
>         Joerg
>
>
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