Re: [PATCH v2] proc: use untagged_addr() for pagemap_read addresses

[Miles Chen]

On Thu, 2020-12-03 at 11:30 +0000, Catalin Marinas wrote:
> On Fri, Nov 27, 2020 at 01:07:38PM +0800, Miles Chen wrote:
> > Cc: Will Deacon <will.deacon@xxxxxxx>
> 
> That should be will@xxxxxxxxxx.

ok, I will fix it and submit v3
> 
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > index 217aa2705d5d..92b277388f05 100644
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -1599,11 +1599,15 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
> >  
> >  	src = *ppos;
> >  	svpfn = src / PM_ENTRY_BYTES;
> > -	start_vaddr = svpfn << PAGE_SHIFT;
> >  	end_vaddr = mm->task_size;
> >  
> >  	/* watch out for wraparound */
> > -	if (svpfn > mm->task_size >> PAGE_SHIFT)
> > +	start_vaddr = end_vaddr;
> > +	if (svpfn < (ULONG_MAX >> PAGE_SHIFT))
> 
> Does this need to be strict less-than? I think a less-than or equal
> would work better.

Thanks, I will fix it and submit v3.
> 
> > +		start_vaddr = untagged_addr(svpfn << PAGE_SHIFT);
> > +
> > +	/* Ensure the address is inside the task */
> > +	if (start_vaddr > mm->task_size)
> >  		start_vaddr = end_vaddr;
> 
> Otherwise the logic looks fine to me. With the above:
> 
> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>