WARNING in close_fs_devices (2)

[syzbot]

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+4cfe71...@syzkaller.appspotmail.com

------------[ 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..


---
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https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[David Sterba]

On Fri, Sep 18, 2020 at 04:22:16AM -0700, 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+4cfe71...@syzkaller.appspotmail.com
>
> ------------[ 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

1152 static int close_fs_devices(struct btrfs_fs_devices *fs_devices)
1153 {
1154 struct btrfs_device *device, *tmp;
1155
1156 if (--fs_devices->opened > 0)
1157 return 0;
1158
1159 mutex_lock(&fs_devices->device_list_mutex);
1160 list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list) {
1161 btrfs_close_one_device(device);
1162 }
1163 mutex_unlock(&fs_devices->device_list_mutex);
1164
1165 WARN_ON(fs_devices->open_devices);
1166 WARN_ON(fs_devices->rw_devices);

1167 fs_devices->opened = 0;
1168 fs_devices->seeding = false;
1169
1170 return 0;
1171 }

It's the 2nd warning, rw_devices > 0 .

> Kernel panic - not syncing: panic_on_warn set ...
> CPU: 1 PID: 3612 Comm: syz-executor.2 Not tainted 5.9.0-rc4-syzkaller #0

5.9-rc4, we've had some changes around device locking but no idea which
one it could be.

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: b652d2a5 Add linux-next specific files for 20200918
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17e84b07900000
kernel config: https://syzkaller.appspot.com/x/.config?x=3cf0782933432b43

dashboard link: https://syzkaller.appspot.com/bug?extid=4cfe71a4da060be47502
compiler: gcc (GCC) 10.1.0-syz 20200507

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=112425d9900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1486929b900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4cfe71...@syzkaller.appspotmail.com

------------[ cut here ]------------

WARNING: CPU: 0 PID: 6972 at fs/btrfs/volumes.c:1172 close_fs_devices+0x715/0x930 fs/btrfs/volumes.c:1172
Modules linked in:
CPU: 1 PID: 6972 Comm: syz-executor044 Not tainted 5.9.0-rc5-next-20200918-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

RIP: 0010:close_fs_devices+0x715/0x930 fs/btrfs/volumes.c:1172
Code: e8 00 b8 4c fe 85 db 0f 85 65 f9 ff ff e8 93 bb 4c fe 0f 0b e9 59 f9 ff ff e8 87 bb 4c fe 0f 0b e9 c0 fe ff ff e8 7b bb 4c fe <0f> 0b e9 f9 fe ff ff 48 c7 c7 fc a1 8f 8b e8 e8 0b 8e fe e9 19 f9
RSP: 0018:ffffc900061b7758 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffffffffffffffff RCX: ffffffff83285c2c
RDX: ffff8880a6bbe4c0 RSI: ffffffff83285d35 RDI: 0000000000000007
RBP: dffffc0000000000 R08: 0000000000000000 R09: ffff8880a2be1133
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880a2be1130
R13: ffff8880a2be11ec R14: ffff888093ab0508 R15: ffff8880a2be1050
FS: 000000000208a880(0000) GS:ffff8880ae500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004babec CR3: 00000000a7bc7000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
btrfs_close_devices+0x8e/0x4b0 fs/btrfs/volumes.c:1184
open_ctree+0x492a/0x49cf fs/btrfs/disk-io.c:3381

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:983 [inline]
vfs_kern_mount.part.0+0xd3/0x170 fs/namespace.c:1013
vfs_kern_mount+0x3c/0x60 fs/namespace.c:1000

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:2896 [inline]
path_mount+0x12ae/0x1e70 fs/namespace.c:3216
do_mount fs/namespace.c:3229 [inline]
__do_sys_mount fs/namespace.c:3437 [inline]
__se_sys_mount fs/namespace.c:3414 [inline]
__x64_sys_mount+0x27f/0x300 fs/namespace.c:3414
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x44851a
Code: b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 cd a2 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 aa a2 fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007ffcb26bce08 EFLAGS: 00000293 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000000044851a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007ffcb26bce50
RBP: 00007ffcb26bce90 R08: 00007ffcb26bce90 R09: 0000000020000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000003
R13: 00007ffcb26bce50 R14: 0000000000000003 R15: 0000000000000001

[Anand Jain]

I am able to reproduce. And its quite strange at the moment. A devid 0
is being scanned. Looks like crafted image.

[19592.946397] BTRFS: device fsid f90cac8b-044b-4fa8-8bee-4b8d3da88dc2
devid 0 transid 0 /dev/loop0 scanned by t (70902)

[Johannes Thumshirn]

Yeah if you look at the C reproducer it crafts an image in memory and
then loop mounts it.

[David Sterba]

On Fri, Sep 18, 2020 at 04:22:16AM -0700, syzbot wrote:

#syz test: git://github.com/kdave/btrfs-devel.git misc-5.9

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in close_fs_devices

BTRFS info (device loop5): enabling ssd optimizations
BTRFS warning (device loop5): failed to read fs tree: -5
------------[ cut here ]------------
WARNING: CPU: 0 PID: 8915 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: 8915 Comm: syz-executor.4 Not tainted 5.8.0-rc7-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+0x18f/0x20d lib/dump_stack.c:118
panic+0x31e/0x797 kernel/panic.c:231
__warn.cold+0x20/0x4a kernel/panic.c:600
report_bug+0x1bd/0x210 lib/bug.c:198
handle_bug+0x38/0x90 arch/x86/kernel/traps.c:235
exc_invalid_op+0x13/0x40 arch/x86/kernel/traps.c:255
asm_exc_invalid_op+0x12/0x20 arch/x86/include/asm/idtentry.h:540

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 e9 19 4d fe <0f> 0b e9 71 ff ff ff e8 dd 19 4d fe 0f 0b e9 20 ff ff ff e8 e1 33
RSP: 0018:ffffc90006777818 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffffffffffffffff RCX: ffffffff83288276
RDX: ffff8880921402c0 RSI: ffffffff83288307 RDI: 0000000000000007
RBP: dffffc0000000000 R08: 0000000000000001 R09: ffff8880a7206c7f
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888095742130
R13: ffff8880957421ec R14: ffff8880a7206d08 R15: ffff888095742050

close_fs_devices fs/btrfs/volumes.c:1193 [inline]
btrfs_close_devices+0x95/0x1f0 fs/btrfs/volumes.c:1179

open_ctree+0x49e6/0x4a96 fs/btrfs/disk-io.c:3456

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]

do_mount+0x159c/0x2000 fs/namespace.c:3200
__do_sys_mount fs/namespace.c:3410 [inline]
__se_sys_mount fs/namespace.c:3387 [inline]
__x64_sys_mount+0x18f/0x230 fs/namespace.c:3387
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384

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:00007f5e059b1a88 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f5e059b1b20 RCX: 000000000046004a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007f5e059b1ae0
RBP: 00007f5e059b1ae0 R08: 00007f5e059b1b20 R09: 0000000020000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000020000000
R13: 0000000020000100 R14: 0000000020000200 R15: 0000000020000140

Kernel Offset: disabled
Rebooting in 86400 seconds..

Tested on:

commit: d1db82c9 btrfs: move btrfs_rm_dev_replace_free_srcdev outs..
git tree: git://github.com/kdave/btrfs-devel.git misc-5.9
console output: https://syzkaller.appspot.com/x/log.txt?x=1007c6c3900000
kernel config: https://syzkaller.appspot.com/x/.config?x=72e4ae28d563b993

[Anand Jain]

#syz fix: btrfs: fix rw_devices count in __btrfs_free_extra_devids

[Dmitry Vyukov]

Is it the correct patch title? It still does not exist anywhere
including linux-next...

[David Sterba]

The patch hasn't been merged yet, the title should be still correct.

[Anand Jain]

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/d0b5790792b8b826504dd239ad9efc514...@oracle.com/


Thanks, Anand

[Dmitry Vyukov]

Thanks for double checking.
I was confused by the fact that the previous patch appeared briefly in
linux-next, but then disappeared.

I see the new patch contains the syzbot tag, so we are all good here.