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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Thu, 2 Apr 2020 16:31:56 +0200
Message-ID: <CACT4Y+YpJt=qMSWKGneTCgzGOErxAE3n3WX+6FYFii2LoBuNQQ@mail.gmail.com>
Subject: Re: WARNING in ext4_da_update_reserve_space
To:     =?UTF-8?Q?Murilo_Opsfelder_Ara=C3=BAjo?= <muriloo@linux.ibm.com>
Cc:     syzbot <syzbot+67e4f16db666b1c8253c@syzkaller.appspotmail.com>,
        a@unstable.cc, Andreas Dilger <adilger.kernel@dilger.ca>,
        b.a.t.m.a.n@lists.open-mesh.org,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        David Miller <davem@davemloft.net>, linux-ext4@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        mareklindner@neomailbox.ch, Michael Ellerman <mpe@ellerman.id.au>,
        netdev <netdev@vger.kernel.org>,
        Paul Mackerras <paulus@samba.org>, sw@simonwunderlich.de,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        "Theodore Ts'o" <tytso@mit.edu>
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On Thu, Apr 2, 2020 at 4:06 PM Murilo Opsfelder Ara=C3=BAjo
<muriloo@linux.ibm.com> wrote:
>
> On Thursday, April 2, 2020 8:02:11 AM -03 syzbot wrote:
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    1a147b74 Merge branch 'DSA-mtu'
> > git tree:       net-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=3D14237713e00=
000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=3D46ee14d4915=
944bc
> > dashboard link: https://syzkaller.appspot.com/bug?extid=3D67e4f16db666b=
1c8253c
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=3D12237713e=
00000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=3D10ec7c97e00=
000
> >
> > The bug was bisected to:
> >
> > commit 658b0f92bc7003bc734471f61bf7cd56339eb8c3
> > Author: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
> > Date:   Wed Aug 1 21:33:15 2018 +0000
> >
> >     powerpc/traps: Print unhandled signals in a separate function
>
> This commit is specific to powerpc and the crash is from an x86_64 system=
.
>
> There is a bunch of scp errors in the logs:
>
> scp: ./syz-executor998635077: No space left on device
>
> Is it possible that these errors might be misleading the syzbot?

You may see how it reacted on them based on
# git bisect bad/good
lines. As far as I see these errors did not confuse it.

But this guy did:
run #0: crashed: general protection fault in batadv_iv_ogm_queue_add


> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=3D15979f5b=
e00000
> > final crash:    https://syzkaller.appspot.com/x/report.txt?x=3D17979f5b=
e00000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=3D13979f5be00=
000
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the comm=
it:
> > Reported-by: syzbot+67e4f16db666b1c8253c@syzkaller.appspotmail.com
> > Fixes: 658b0f92bc70 ("powerpc/traps: Print unhandled signals in a separ=
ate
> > function")
> >
> > EXT4-fs warning (device sda1): ext4_da_update_reserve_space:344:
> > ext4_da_update_reserve_space: ino 15722, used 1 with only 0 reserved da=
ta
> > blocks ------------[ cut here ]------------
> > WARNING: CPU: 1 PID: 359 at fs/ext4/inode.c:348
> > ext4_da_update_reserve_space+0x622/0x7d0 fs/ext4/inode.c:344 Kernel pan=
ic -
> > not syncing: panic_on_warn set ...
> > CPU: 1 PID: 359 Comm: kworker/u4:5 Not tainted 5.6.0-rc7-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011 Workqueue: writeback wb_workfn (flush-8:0)
> > Call Trace:
> >  __dump_stack lib/dump_stack.c:77 [inline]
> >  dump_stack+0x188/0x20d lib/dump_stack.c:118
> >  panic+0x2e3/0x75c kernel/panic.c:221
> >  __warn.cold+0x2f/0x35 kernel/panic.c:582
> >  report_bug+0x27b/0x2f0 lib/bug.c:195
> >  fixup_bug arch/x86/kernel/traps.c:174 [inline]
> >  fixup_bug arch/x86/kernel/traps.c:169 [inline]
> >  do_error_trap+0x12b/0x220 arch/x86/kernel/traps.c:267
> >  do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286
> >  invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
> > RIP: 0010:ext4_da_update_reserve_space+0x622/0x7d0 fs/ext4/inode.c:348
> > Code: 02 00 0f 85 94 01 00 00 48 8b 7d 28 49 c7 c0 20 72 3c 88 41 56 48=
 c7
> > c1 80 60 3c 88 53 ba 58 01 00 00 4c 89 c6 e8 1e 6d 0d 00 <0f> 0b 48 b8 =
00
> > 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 0f b6 04 RSP:
> > 0018:ffffc90002197288 EFLAGS: 00010296
> > RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000
> > RDX: 0000000000000000 RSI: ffffffff820bf066 RDI: fffff52000432e21
> > RBP: ffff888086b744c8 R08: 0000000000000091 R09: ffffed1015ce6659
> > R10: ffffed1015ce6658 R11: ffff8880ae7332c7 R12: 0000000000000001
> > R13: ffff888086b74990 R14: 0000000000000000 R15: ffff888086b74a40
> >  ext4_ext_map_blocks+0x24aa/0x37d0 fs/ext4/extents.c:4500
> >  ext4_map_blocks+0x4cb/0x1650 fs/ext4/inode.c:622
> >  mpage_map_one_extent fs/ext4/inode.c:2365 [inline]
> >  mpage_map_and_submit_extent fs/ext4/inode.c:2418 [inline]
> >  ext4_writepages+0x19eb/0x3080 fs/ext4/inode.c:2772
> >  do_writepages+0xfa/0x2a0 mm/page-writeback.c:2344
> >  __writeback_single_inode+0x12a/0x1410 fs/fs-writeback.c:1452
> >  writeback_sb_inodes+0x515/0xdd0 fs/fs-writeback.c:1716
> >  wb_writeback+0x2a5/0xd90 fs/fs-writeback.c:1892
> >  wb_do_writeback fs/fs-writeback.c:2037 [inline]
> >  wb_workfn+0x339/0x11c0 fs/fs-writeback.c:2078
> >  process_one_work+0x94b/0x1690 kernel/workqueue.c:2266
> >  worker_thread+0x96/0xe20 kernel/workqueue.c:2412
> >  kthread+0x357/0x430 kernel/kthread.c:255
> >  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
> > Kernel Offset: disabled
> > Rebooting in 86400 seconds..
> >
> >
> > ---
> > This bug is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@googlegroups.com.
> >
> > syzbot will keep track of this bug report. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > For information about bisection process see: https://goo.gl/tpsmEJ#bise=
ction
> > syzbot can test patches for this bug, for details see:
> > https://goo.gl/tpsmEJ#testing-patches
>
> --
> Murilo
>
> --
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