linux-kernel - Re: [PATCH v12 10/11] sparc64: Add support for ADI (Application Data Integrity)

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Date:   Mon, 5 Mar 2018 14:14:50 -0700
From:   Khalid Aziz <khalid.aziz@...cle.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>, davem@...emloft.net,
        akpm@...ux-foundation.org
Cc:     corbet@....net, bob.picco@...cle.com, steven.sistare@...cle.com,
        pasha.tatashin@...cle.com, mike.kravetz@...cle.com,
        rob.gardner@...cle.com, mingo@...nel.org, nitin.m.gupta@...cle.com,
        anthony.yznaga@...cle.com, kirill.shutemov@...ux.intel.com,
        tom.hromatka@...cle.com, allen.pais@...cle.com,
        tklauser@...tanz.ch, shannon.nelson@...cle.com,
        vijay.ac.kumar@...cle.com, mhocko@...e.com, jack@...e.cz,
        punit.agrawal@....com, hughd@...gle.com, thomas.tai@...cle.com,
        ross.zwisler@...ux.intel.com, dave.jiang@...el.com,
        willy@...radead.org, minchan@...nel.org,
        imbrenda@...ux.vnet.ibm.com, aarcange@...hat.com,
        kstewart@...uxfoundation.org, pombredanne@...b.com,
        tglx@...utronix.de, gregkh@...uxfoundation.org,
        nagarathnam.muthusamy@...cle.com, linux@...ck-us.net,
        jane.chu@...cle.com, dan.j.williams@...el.com, jglisse@...hat.com,
        ktkhai@...tuozzo.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        sparclinux@...r.kernel.org, Khalid Aziz <khalid@...ehiking.org>
Subject: Re: [PATCH v12 10/11] sparc64: Add support for ADI (Application Data
 Integrity)

On 03/05/2018 12:22 PM, Dave Hansen wrote:
> On 02/21/2018 09:15 AM, Khalid Aziz wrote:
>> +#define arch_validate_prot(prot, addr) sparc_validate_prot(prot, addr)
>> +static inline int sparc_validate_prot(unsigned long prot, unsigned long addr)
>> +{
>> +	if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM | PROT_ADI))
>> +		return 0;
>> +	if (prot & PROT_ADI) {
>> +		if (!adi_capable())
>> +			return 0;
>> +
>> +		if (addr) {
>> +			struct vm_area_struct *vma;
>> +
>> +			vma = find_vma(current->mm, addr);
>> +			if (vma) {
>> +				/* ADI can not be enabled on PFN
>> +				 * mapped pages
>> +				 */
>> +				if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
>> +					return 0;
> 
> You don't hold mmap_sem here.  How can this work?
>

Are you suggesting that vma returned by find_vma() could be split or 
merged underneath me if I do not hold mmap_sem and thus make the flag 
check invalid? If so, that is a good point.

Thanks,
Khalid