linux-kernel - Re: [PATCH v2 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit

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Date:   Wed, 26 Jan 2022 22:38:04 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Fenghua Yu <fenghua.yu@...el.com>
Cc:     Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        iommu@...ts.linux-foundation.org, x86 <x86@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 05/11] iommu/sva: Assign a PASID to mm on PASID
 allocation and free it on mm exit

On Wed, Jan 26 2022 at 09:36, Fenghua Yu wrote:
> On Wed, Jan 26, 2022 at 03:23:42PM +0100, Thomas Gleixner wrote:
>> On Tue, Jan 25 2022 at 07:18, Fenghua Yu wrote:
>> While looking at ioasid_put() usage I tripped over the following UAF
>> issue:
>> 
>> --- a/drivers/iommu/intel/iommu.c
>> +++ b/drivers/iommu/intel/iommu.c
>> @@ -4817,8 +4817,10 @@ static int aux_domain_add_dev(struct dma
>>  	auxiliary_unlink_device(domain, dev);
>>  link_failed:
>>  	spin_unlock_irqrestore(&device_domain_lock, flags);
>> -	if (list_empty(&domain->subdevices) && domain->default_pasid > 0)
>> +	if (list_empty(&domain->subdevices) && domain->default_pasid > 0) {
>>  		ioasid_put(domain->default_pasid);
>> +		domain->default_pasid = INVALID_IOASID;
>> +	}
>>  
>>  	return ret;
>>  }
>> @@ -4847,8 +4849,10 @@ static void aux_domain_remove_dev(struct
>>  
>>  	spin_unlock_irqrestore(&device_domain_lock, flags);
>>  
>> -	if (list_empty(&domain->subdevices) && domain->default_pasid > 0)
>> +	if (list_empty(&domain->subdevices) && domain->default_pasid > 0) {
>>  		ioasid_put(domain->default_pasid);
>> +		domain->default_pasid = INVALID_IOASID;
>> +	}
>>  }
>>  
>>  static int prepare_domain_attach_device(struct iommu_domain *domain,
>
> The above patch fixes an existing issue. I will put it in a separate patch,
> right?

Correct.

> It cannot be applied cleanly to the upstream tree. Do you want me to base
> the above patch (and the whole patch set) to the upstream tree or a specific
> tip branch?

Against Linus tree please so that the bugfix applies.

> I will fold the following patch into patch #5. The patch #11 (the doc patch)
> also needs to remove one paragraph talking about refcount.
>
> So I will send the whole patch set with the following changes:
> 1. One new bug fix patch (the above patch)
> 2. Updated patch #5 (with the following patch folded)
> 3. Updated patch #11 (removing refcount description)

Looks good.

Thanks,

        tglx