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In-Reply-To: <761793f4-cd16-fcc1-8777-f7e032604e1e@nvidia.com>
From:   Aleksandr Nogikh <nogikh@google.com>
Date:   Wed, 31 Aug 2022 11:40:54 +0200
Message-ID: <CANp29Y6Wk21aqLjJ2ygTykZgqZ+3=1kQks6cTYrB_=TVRQqghw@mail.gmail.com>
Subject: Re: [syzbot] general protection fault in vma_is_shmem
To:     John Hubbard <jhubbard@nvidia.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        syzbot <syzbot+681bbbb80445ead3c040@syzkaller.appspotmail.com>,
        hughd@google.com, LKML <linux-kernel@vger.kernel.org>,
        linux-mm@kvack.org,
        "'Aleksandr Nogikh' via syzkaller-bugs" 
        <syzkaller-bugs@googlegroups.com>,
        Alistair Popple <apopple@nvidia.com>,
        David Hildenbrand <david@redhat.com>,
        Jason Gunthorpe <jgg@nvidia.com>
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Let's tell syzbot about the fix

#syz fix: mm/gup.c: Fix return value for __gup_longterm_locked()

On Mon, Aug 22, 2022 at 2:10 AM 'John Hubbard' via syzkaller-bugs
<syzkaller-bugs@googlegroups.com> wrote:
>
> On 8/21/22 16:31, Andrew Morton wrote:
> > On Sun, 21 Aug 2022 16:18:48 -0700 John Hubbard <jhubbard@nvidia.com> wrote:
> >
> >>> vmas[] array.  We haven't messed with gup.c much this time around -
> >>> just one patch from Alistair ("mm/gup.c: simplify and fix
> >>> check_and_migrate_movable_pages() return codes").  It does touch this
> >>> area, but I can't immediately see how it could newly cause this.
> >>>
> >>
> >> Neither can I, even after looking at both of these recent commits to
> >> gup.c in this branch:
> >>
> >> commit 4d1225cd5560 ("mm/gup.c: simplify and fix
> >> check_and_migrate_movable_pages() return codes")
> >>
> >> commit 0e5d6dac6b65 ("mm/gup: fix FOLL_FORCE COW security issue and
> >> remove FOLL_COW")
> >>
> >> As you say, a bisection would really help here.
> >
> > Might
> > https://lkml.kernel.org/r/20220821183547.950370-1-syoshida@redhat.com
> > save us?
> >
> >
>
> aha yes, that looks right.
>
>
> thanks,
> --
> John Hubbard
> NVIDIA
>
> --
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