linux-kernel - Re: [syzbot] WARNING in mark_buffer

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Date:   Mon, 4 Jul 2022 15:13:13 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     syzbot <syzbot+2af3bc9585be7f23f290@...kaller.appspotmail.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, viro@...iv.linux.org.uk
Subject: Re: [syzbot] WARNING in mark_buffer_dirty (4)

On Mon, 4 Jul 2022 at 12:56, Matthew Wilcox <willy@...radead.org> wrote:
>
> On Mon, Jul 04, 2022 at 03:22:22AM -0700, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    d9b2ba67917c Merge tag 'platform-drivers-x86-v5.19-3' of g..
> > git tree:       upstream
> > console+strace: https://syzkaller.appspot.com/x/log.txt?x=15d5f0f0080000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=3a010dbf6a7af480
> > dashboard link: https://syzkaller.appspot.com/bug?extid=2af3bc9585be7f23f290
> > compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14464f70080000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1779a598080000
> >
> > Bisection is inconclusive: the first bad commit could be any of:
> >
> > a1a98689301b drm: Add privacy-screen class (v4)
> > befe5404a00b drm/privacy-screen: Add X86 specific arch init code
> > 107fe9043020 drm/connector: Add support for privacy-screen properties (v4)
> > 8a12b170558a drm/privacy-screen: Add notifier support (v2)
> > 334f74ee85dc drm/connector: Add a drm_connector privacy-screen helper functions (v2)
>
> It's clearly none of those commits.  This is a bug in minix, afaict.
> Judging by the earlier errors, I'd say that it tried to read something,
> failed, then marked it dirty, at which point we hit an assertion that
> you shouldn't mark a !uptodate buffer as dirty.  Given that this is
> minix, I have no interest in pursuing this bug further.  Why is syzbot
> even testing with minix?

Shouldn't it? Why? It does not seem to depend on BROKEN.

> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=14a2e85c080000
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+2af3bc9585be7f23f290@...kaller.appspotmail.com
> >
> > WARNING: CPU: 0 PID: 3647 at fs/buffer.c:1081 mark_buffer_dirty+0x59d/0xa20 fs/buffer.c:1081
> > Modules linked in:
> > CPU: 1 PID: 3647 Comm: syz-executor864 Not tainted 5.19.0-rc4-syzkaller-00036-gd9b2ba67917c #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > RIP: 0010:mark_buffer_dirty+0x59d/0xa20 fs/buffer.c:1081
> > Code: 89 ee 41 83 e6 01 4c 89 f6 e8 8f c2 94 ff 4d 85 f6 0f 84 7a fe ff ff e8 21 c6 94 ff 49 8d 5d ff e9 6c fe ff ff e8 13 c6 94 ff <0f> 0b e9 ac fa ff ff e8 07 c6 94 ff 0f 0b e9 d0 fa ff ff e8 fb c5
> > RSP: 0018:ffffc900030c7d30 EFLAGS: 00010293
> > RAX: 0000000000000000 RBX: ffff88806e7bda38 RCX: 0000000000000000
> > RDX: ffff888071720100 RSI: ffffffff81e4d16d RDI: 0000000000000001
> > RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000001 R12: ffff88807c21e7d8
> > R13: 0000000000000000 R14: 0000000000000000 R15: ffffed100f314eda
> > FS:  00007fe4fb903700(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007fe4fb925000 CR3: 0000000079e8a000 CR4: 00000000003506e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >  <TASK>
> >  minix_put_super+0x199/0x500 fs/minix/inode.c:49
> >  generic_shutdown_super+0x14c/0x400 fs/super.c:462
> >  kill_block_super+0x97/0xf0 fs/super.c:1394
> >  deactivate_locked_super+0x94/0x160 fs/super.c:332
> >  deactivate_super+0xad/0xd0 fs/super.c:363
> >  cleanup_mnt+0x3a2/0x540 fs/namespace.c:1186
> >  task_work_run+0xdd/0x1a0 kernel/task_work.c:177
> >  ptrace_notify+0x114/0x140 kernel/signal.c:2353
> >  ptrace_report_syscall include/linux/ptrace.h:420 [inline]
> >  ptrace_report_syscall_exit include/linux/ptrace.h:482 [inline]
> >  syscall_exit_work kernel/entry/common.c:249 [inline]
> >  syscall_exit_to_user_mode_prepare+0xdb/0x230 kernel/entry/common.c:276
> >  __syscall_exit_to_user_mode_work kernel/entry/common.c:281 [inline]
> >  syscall_exit_to_user_mode+0x9/0x50 kernel/entry/common.c:294
> >  do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
> >  entry_SYSCALL_64_after_hwframe+0x46/0xb0
> > RIP: 0033:0x7fe4fb9774c9
> > Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> > RSP: 002b:00007fe4fb9032f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
> > RAX: ffffffffffffffec RBX: 00007fe4fb9fc3f0 RCX: 00007fe4fb9774c9
> > RDX: 0000000020000140 RSI: 00000000200000c0 RDI: 00000000200002c0
> > RBP: 00007fe4fb9c90a8 R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
> > R13: 6f6f6c2f7665642f R14: 000000807fffffff R15: 00007fe4fb9fc3f8
> >  </TASK>
> >
> >
> > ---
> > This report 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@...glegroups.com.
> >
> > syzbot will keep track of this issue. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> > syzbot can test patches for this issue, for details see:
> > https://goo.gl/tpsmEJ#testing-patches
>
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