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Date:   Mon, 4 Jul 2022 11:56:00 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     syzbot <syzbot+2af3bc9585be7f23f290@syzkaller.appspotmail.com>
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk
Subject: Re: [syzbot] WARNING in mark_buffer_dirty (4)
Message-ID: <YsLHQCvp8W5oObv2@casper.infradead.org>
References: <0000000000008f6f7405e2f81ce9@google.com>
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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?

> 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@syzkaller.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@googlegroups.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