Re: WARNING in close_fs_devices (2)

[Anand Jain]

On 30/10/20 6:10 pm, Dmitry Vyukov wrote:
> On Tue, Sep 22, 2020 at 2:37 PM Anand Jain <anand.jain@xxxxxxxxxx> wrote:
> > On 18/9/20 7:22 pm, syzbot wrote:
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit:    e4c26faa Merge tag 'usb-5.9-rc5' of git://git.kernel.org/p..
> > > git tree:       upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=15bf1621900000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=c61610091f4ca8c4
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=4cfe71a4da060be47502
> > > compiler:       gcc (GCC) 10.1.0-syz 20200507
> > >
> > > Unfortunately, I don't have any reproducer for this issue yet.
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+4cfe71a4da060be47502@xxxxxxxxxxxxxxxxxxxxxxxxx
> > >
> > > ------------[ cut here ]------------
> > > WARNING: CPU: 1 PID: 3612 at fs/btrfs/volumes.c:1166 close_fs_devices.part.0+0x607/0x800 fs/btrfs/volumes.c:1166
> > > Kernel panic - not syncing: panic_on_warn set ...
> > > CPU: 1 PID: 3612 Comm: syz-executor.2 Not tainted 5.9.0-rc4-syzkaller #0
> > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > > Call Trace:
> > >    __dump_stack lib/dump_stack.c:77 [inline]
> > >    dump_stack+0x198/0x1fd lib/dump_stack.c:118
> > >    panic+0x347/0x7c0 kernel/panic.c:231
> > >    __warn.cold+0x20/0x46 kernel/panic.c:600
> > >    report_bug+0x1bd/0x210 lib/bug.c:198
> > >    handle_bug+0x38/0x90 arch/x86/kernel/traps.c:234
> > >    exc_invalid_op+0x14/0x40 arch/x86/kernel/traps.c:254
> > >    asm_exc_invalid_op+0x12/0x20 arch/x86/include/asm/idtentry.h:536
> > > RIP: 0010:close_fs_devices.part.0+0x607/0x800 fs/btrfs/volumes.c:1166
> > > Code: 0f b6 04 02 84 c0 74 02 7e 33 48 8b 44 24 18 c6 80 30 01 00 00 00 48 83 c4 30 5b 5d 41 5c 41 5d 41 5e 41 5f c3 e8 99 ce 6a fe <0f> 0b e9 71 ff ff ff e8 8d ce 6a fe 0f 0b e9 20 ff ff ff e8 d1 d5
> > > RSP: 0018:ffffc900091777e0 EFLAGS: 00010246
> > > RAX: 0000000000040000 RBX: ffffffffffffffff RCX: ffffc9000c8b7000
> > > RDX: 0000000000040000 RSI: ffffffff83097f47 RDI: 0000000000000007
> > > RBP: dffffc0000000000 R08: 0000000000000001 R09: ffff8880988a187f
> > > R10: 0000000000000000 R11: 0000000000000001 R12: ffff88809593a130
> > > R13: ffff88809593a1ec R14: ffff8880988a1908 R15: ffff88809593a050
> > >    close_fs_devices fs/btrfs/volumes.c:1193 [inline]
> > >    btrfs_close_devices+0x95/0x1f0 fs/btrfs/volumes.c:1179
> > >    open_ctree+0x4984/0x4a2d fs/btrfs/disk-io.c:3434
> > >    btrfs_fill_super fs/btrfs/super.c:1316 [inline]
> > >    btrfs_mount_root.cold+0x14/0x165 fs/btrfs/super.c:1672
> > >    legacy_get_tree+0x105/0x220 fs/fs_context.c:592
> > >    vfs_get_tree+0x89/0x2f0 fs/super.c:1547
> > >    fc_mount fs/namespace.c:978 [inline]
> > >    vfs_kern_mount.part.0+0xd3/0x170 fs/namespace.c:1008
> > >    vfs_kern_mount+0x3c/0x60 fs/namespace.c:995
> > >    btrfs_mount+0x234/0xaa0 fs/btrfs/super.c:1732
> > >    legacy_get_tree+0x105/0x220 fs/fs_context.c:592
> > >    vfs_get_tree+0x89/0x2f0 fs/super.c:1547
> > >    do_new_mount fs/namespace.c:2875 [inline]
> > >    path_mount+0x1387/0x2070 fs/namespace.c:3192
> > >    do_mount fs/namespace.c:3205 [inline]
> > >    __do_sys_mount fs/namespace.c:3413 [inline]
> > >    __se_sys_mount fs/namespace.c:3390 [inline]
> > >    __x64_sys_mount+0x27f/0x300 fs/namespace.c:3390
> > >    do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
> > >    entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > > RIP: 0033:0x46004a
> > > Code: b8 a6 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 fd 89 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 da 89 fb ff c3 66 0f 1f 84 00 00 00 00 00
> > > RSP: 002b:00007f414d78da88 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
> > > RAX: ffffffffffffffda RBX: 00007f414d78db20 RCX: 000000000046004a
> > > RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007f414d78dae0
> > > RBP: 00007f414d78dae0 R08: 00007f414d78db20 R09: 0000000020000000
> > > R10: 0000000000000000 R11: 0000000000000202 R12: 0000000020000000
> > > R13: 0000000020000100 R14: 0000000020000200 R15: 000000002001a800
> > > Kernel Offset: disabled
> > > Rebooting in 86400 seconds..
> >
> >
> > #syz fix: btrfs: fix rw_devices count in __btrfs_free_extra_devids
>
> Is it the correct patch title? It still does not exist anywhere
> including linux-next...

V2 is here [1]. The patch title is changed. Also the cover letter talks 
about the path dependency. It is not yet integrated.

[1]
https://patchwork.kernel.org/project/linux-btrfs/patch/d0b5790792b8b826504dd239ad9efc514f3d9109.1604009248.git.anand.jain@xxxxxxxxxx/


Thanks, Anand