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From:   Aleksandr Nogikh <nogikh@google.com>
Date:   Thu, 5 Jan 2023 12:14:17 +0100
Message-ID: <CANp29Y63rCdepVtantxdJEcvbRv0D61gfY_oGV7dgrmEGgPdLw@mail.gmail.com>
Subject: Re: [syzbot] [erofs?] WARNING: CPU: NUM PID: NUM at
 mm/page_alloc.c:LINE get_page_from_freeli
To:     Xiang Gao <hsiangkao@linux.alibaba.com>
Cc:     syzbot <syzbot+c3729cda01706a04fb98@syzkaller.appspotmail.com>,
        akpm@linux-foundation.org, chao@kernel.org,
        linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com, xiang@kernel.org
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Hi,

On Thu, Jan 5, 2023 at 11:54 AM Xiang Gao <hsiangkao@linux.alibaba.com> wrote:

> I wasn't able to build the kernel with this kernel config, it shows:
> "...
> FATAL: modpost: vmlinux.o is truncated. sechdrs[i].sh_offset=1399394064 > sizeof(*hrd)=64
> make[2]: *** [Module.symvers] Error 1
> make[1]: *** [modpost] Error 2
> make: *** [__sub-make] Error 2
> "

Could you please tell, what exact compiler/linker version did you use?


> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/0c8a5f06ceb3/disk-f9ff5644.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/be222e852ae2/vmlinux-f9ff5644.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/d9f42a53b05e/bzImage-f9ff5644.xz
>
> Finally I tried the original kernel image, and it printed some other
> random bug when booting system and then reboot, like:
>
> [   36.991123][    T1] ==================================================================
> [   36.991800][    T1] BUG: KASAN: slab-out-of-bounds in copy_array+0x96/0x100
> [   36.992438][    T1] Write of size 32 at addr ffff888018c34640 by task systemd/1
< .. >

Interesting!
I've just tried to boot it with qemu and it was fine.

qemu-system-x86_64 -smp 2,sockets=2,cores=1 -m 4G -drive
file=disk-f9ff5644.raw,format=raw -snapshot -nographic -enable-kvm

So it looks like it's some difference between these VMMs that causes
that bug to fire.

>
> May I ask it can be reproducable on the latest -rc kernel?

We can ask syzbot about v6.2-rc2:

#syz test git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
88603b6dc419445847923fcb7fe5080067a30f98

>
> Thanks,
> Gao Xiang
>

--
Aleksandr