linux-kernel - Re: [PATCH v8 1/5] iommu/arm-smmu: Destroy domain context in failure path

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Message-ID: <CAFp+6iH7DdMnG2oMXWDGXNUjQsB1aPwOXEnrfHR-VoJzzqUPUA@mail.gmail.com>
Date:   Thu, 8 Mar 2018 11:02:49 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>," <joro@...tes.org>,
        "robh+dt" <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Will Deacon <will.deacon@....com>,
        Rob Clark <robdclark@...il.com>,
        "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>," <iommu@...ts.linux-foundation.org>,
        devicetree@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>,
        Tomasz Figa <tfiga@...omium.org>, jcrouse@...eaurora.org,
        Stephen Boyd <sboyd@...eaurora.org>,
        Sricharan R <sricharan@...eaurora.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Archit Taneja <architt@...eaurora.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v8 1/5] iommu/arm-smmu: Destroy domain context in failure path

On Wed, Mar 7, 2018 at 5:50 PM, Robin Murphy <robin.murphy@....com> wrote:
> On 02/03/18 10:10, Vivek Gautam wrote:
>>
>> If we fail after initializing domain_context, we should destroy
>> the context to free up resources.
>
>
> Have another think about why the "problem" this patch caters for cannot ever
> happen (hint: consider how domain->smmu is used in
> arm_smmu_init_domain_context()). And then also about the really
> catastrophically bad problem it actually introduces (hint:
> "iommu_attach(domain, good_dev); iommu_attach(domain, bad_dev);")

Got it, we would end up destroying good_dev's domain context with this.
Thanks

regards
Vivek

>
> Robin.
>
>
>> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
>> ---
>>
>>   * New patch added in this series.
>>
>>   drivers/iommu/arm-smmu.c | 7 ++++++-
>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
>> index 69e7c60792a8..ffc152c36002 100644
>> --- a/drivers/iommu/arm-smmu.c
>> +++ b/drivers/iommu/arm-smmu.c
>> @@ -1223,11 +1223,16 @@ static int arm_smmu_attach_dev(struct iommu_domain
>> *domain, struct device *dev)
>>                 dev_err(dev,
>>                         "cannot attach to SMMU %s whilst already attached
>> to domain on SMMU %s\n",
>>                         dev_name(smmu_domain->smmu->dev),
>> dev_name(smmu->dev));
>> -               return -EINVAL;
>> +               ret = -EINVAL;
>> +               goto destroy_domain;
>>         }
>>         /* Looks ok, so add the device to the domain */
>>         return arm_smmu_domain_add_master(smmu_domain, fwspec);
>> +
>> +destroy_domain:
>> +       arm_smmu_destroy_domain_context(domain);
>> +       return ret;
>>   }
>>     static int arm_smmu_map(struct iommu_domain *domain, unsigned long
>> iova,
>>
>



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