linux-kernel - Re: [PATCH 3/7] mm/gup: remove vmas parameter from get_user_pages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

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.