linux-kernel - Re: [PATCH v2] proc: use untagged_addr() for pagemap

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Date:   Fri, 4 Dec 2020 09:34:08 +0800
From:   Miles Chen <miles.chen@...iatek.com>
To:     Catalin Marinas <catalin.marinas@....com>
CC:     Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <wsd_upstream@...iatek.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Marco Elver <elver@...gle.com>,
        "Will Deacon" <will@...nel.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Song Bao Hua <song.bao.hua@...ilicon.com>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH v2] proc: use untagged_addr() for pagemap_read addresses

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@....com>
> 
> That should be will@...nel.org.

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@....com>