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

[Khalid Aziz]

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