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Message-ID: <e712589f-f4c0-4037-8a3c-0d48bd35baef@lucifer.local>
Date: Sat, 15 Apr 2023 09:11:20 +0100
From: Lorenzo Stoakes <lstoakes@...il.com>
To: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] mm/gup: remove vmas parameter from
get_user_pages_remote()
On Sat, Apr 15, 2023 at 09:25:51AM +0900, Tetsuo Handa wrote:
> On 2023/04/15 8:27, Lorenzo Stoakes wrote:
> > diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
> > index f5bcb0dc6267..74d8d4007dec 100644
> > --- a/arch/arm64/kernel/mte.c
> > +++ b/arch/arm64/kernel/mte.c
> > @@ -437,8 +437,9 @@ static int __access_remote_tags(struct mm_struct *mm, unsigned long addr,
> > struct page *page = NULL;
> >
> > ret = get_user_pages_remote(mm, addr, 1, gup_flags, &page,
> > - &vma, NULL);
> > - if (ret <= 0)
> > + NULL);
> > + vma = vma_lookup(mm, addr);
> > + if (ret <= 0 || !vma)
> > break;
>
> This conversion looks wrong. When get_user_pages_remote(&page) returned > 0,
> put_page(page) is needed even if vma_lookup() returned NULL, isn't it?
>
You're right, though actually it's not possible for ret > 0 and vma != NULL
because the GUP code requires the VMA to exist for it to have returned > 0.
I was trying to be too cute here I think, actually we only want to be doing
that lookup if the GUP succeeded in any case.
Let me respin with a fix for this.
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