[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAJuCfpG5T71Sc46pB2eGpV7TreMZX2VZ-kDfaNmtn+etP0q9JA@mail.gmail.com>
Date: Thu, 11 Jan 2024 20:20:22 +0000
From: Suren Baghdasaryan <surenb@...gle.com>
To: David Hildenbrand <david@...hat.com>
Cc: syzbot <syzbot+705209281e36404998f6@...kaller.appspotmail.com>,
Peter Xu <peterx@...hat.com>, aarcange@...hat.com, akpm@...ux-foundation.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm?] kernel BUG in move_pages
On Thu, Jan 11, 2024 at 6:58 PM David Hildenbrand <david@...hat.com> wrote:
>
> On 11.01.24 19:34, Suren Baghdasaryan wrote:
> > On Thu, Jan 11, 2024 at 8:44 AM Suren Baghdasaryan <surenb@...gle.com> wrote:
> >>
> >> On Thu, Jan 11, 2024 at 8:40 AM Suren Baghdasaryan <surenb@...gle.com> wrote:
> >>>
> >>> On Thu, Jan 11, 2024 at 8:25 AM syzbot
> >>> <syzbot+705209281e36404998f6@...kaller.appspotmail.com> wrote:
> >>>>
> >>>> Hello,
> >>>>
> >>>> syzbot found the following issue on:
> >>>>
> >>>> HEAD commit: e2425464bc87 Add linux-next specific files for 20240105
> >>>> git tree: linux-next
> >>>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=14941cdee80000
> >>>> kernel config: https://syzkaller.appspot.com/x/.config?x=4056b9349f3da8c9
> >>>> dashboard link: https://syzkaller.appspot.com/bug?extid=705209281e36404998f6
> >>>> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> >>>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=125d0a09e80000
> >>>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15bc7331e80000
> >>>>
> >>>> Downloadable assets:
> >>>> disk image: https://storage.googleapis.com/syzbot-assets/2f738185e2cf/disk-e2425464.raw.xz
> >>>> vmlinux: https://storage.googleapis.com/syzbot-assets/b248fcf4ea46/vmlinux-e2425464.xz
> >>>> kernel image: https://storage.googleapis.com/syzbot-assets/a9945c8223f4/bzImage-e2425464.xz
> >>>>
> >>>> The issue was bisected to:
> >>>>
> >>>> commit adef440691bab824e39c1b17382322d195e1fab0
> >>>> Author: Andrea Arcangeli <aarcange@...hat.com>
> >>>> Date: Wed Dec 6 10:36:56 2023 +0000
> >>>>
> >>>> userfaultfd: UFFDIO_MOVE uABI
> >>>>
> >>>> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11cb6ea9e80000
> >>>> final oops: https://syzkaller.appspot.com/x/report.txt?x=13cb6ea9e80000
> >>>> console output: https://syzkaller.appspot.com/x/log.txt?x=15cb6ea9e80000
> >>>>
> >>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> >>>> Reported-by: syzbot+705209281e36404998f6@...kaller.appspotmail.com
> >>>> Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI")
> >>>>
> >>>> do_one_initcall+0x128/0x680 init/main.c:1237
> >>>> do_initcall_level init/main.c:1299 [inline]
> >>>> do_initcalls init/main.c:1315 [inline]
> >>>> do_basic_setup init/main.c:1334 [inline]
> >>>> kernel_init_freeable+0x692/0xc30 init/main.c:1552
> >>>> kernel_init+0x1c/0x2a0 init/main.c:1442
> >>>> ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
> >>>> ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
> >>>> ------------[ cut here ]------------
> >>>> kernel BUG at include/linux/page-flags.h:1035!
> >>>> invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> >>>> CPU: 0 PID: 5068 Comm: syz-executor191 Not tainted 6.7.0-rc8-next-20240105-syzkaller #0
> >>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
> >>>> RIP: 0010:PageAnonExclusive include/linux/page-flags.h:1035 [inline]
> >>>
> >>> From a quick look, I think the new ioctl is being used against a
> >>> file-backed page and that's why PageAnonExclusive() throws this error.
> >>> I'll confirm if this is indeed the case and will add checks for that
> >>> case. Thanks!
> >>
> >> Hmm. Looking at the reproducer it does not look like a file-backed
> >> memory... Anyways, I'm on it.
> >
> > Looks like the test is trying to move the huge_zero_page. Wonder how
> > we should handle this. Just fail or do something else? Adding David
> > and Peter for feedback.
>
> You'll need some special-casing to handle that. But it should be fairly
> easy.
Ok, so should we treat zeropage the same as PAE and map destination
PTE/PMD to zeropage while clearing source PTE/PMD?
>
> --
> Cheers,
>
> David / dhildenb
>
Powered by blists - more mailing lists