BUG: Dentry ADDR{i=0,n=/} still in use (-128) [unmount of erofs loop5]

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3c8c2309 Linux 4.19.190
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17d8d795d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=d3c2572d41264a3d
dashboard link: https://syzkaller.appspot.com/bug?extid=9a2e823528e0a25d7c06
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10b770a3d00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15b98f2dd00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9a2e82...@syzkaller.appspotmail.com

RBP: 0000000000000003 R08: 00007f4576e740d0 R09: 00007f4576e746bc
R10: 0000000000000000 R11: 0000000000000286 R12: 00007f4576e74090
R13: 0000000020000248 R14: 0000000000000005 R15: 0000000000000006
CPU: 1 PID: 8150 Comm: syz-executor899 Not tainted 4.19.190-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
BUG: Dentry 00000000df64a627{i=0,n=/} still in use (-128) [unmount of erofs loop5]
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
fail_dump lib/fault-inject.c:51 [inline]
should_fail.cold+0xa/0xf lib/fault-inject.c:149
__should_failslab+0x115/0x180 mm/failslab.c:32
should_failslab+0x5/0x10 mm/slab_common.c:1588
slab_pre_alloc_hook mm/slab.h:424 [inline]
slab_alloc mm/slab.c:3383 [inline]
__do_kmalloc mm/slab.c:3725 [inline]
__kmalloc_track_caller+0x2a6/0x3c0 mm/slab.c:3742
kstrdup+0x36/0x70 mm/util.c:56
kstrdup_const+0x53/0x80 mm/util.c:77
alloc_vfsmnt+0xb5/0x780 fs/namespace.c:188
clone_mnt+0x6c/0x11b0 fs/namespace.c:1001
------------[ cut here ]------------
WARNING: CPU: 0 PID: 8161 at fs/dcache.c:1518 umount_check fs/dcache.c:1518 [inline]
WARNING: CPU: 0 PID: 8161 at fs/dcache.c:1518 umount_check.cold+0xf2/0x116 fs/dcache.c:1499
Kernel panic - not syncing: panic_on_warn set ...

copy_tree+0x100/0xaf0 fs/namespace.c:1722
propagate_one.part.0+0x3a8/0x710 fs/pnode.c:265
propagate_one fs/pnode.c:234 [inline]
propagate_mnt+0x40d/0x530 fs/pnode.c:325
attach_recursive_mnt+0x697/0xd80 fs/namespace.c:1984
graft_tree+0x187/0x210 fs/namespace.c:2084
do_add_mount+0x239/0x560 fs/namespace.c:2442
do_new_mount fs/namespace.c:2483 [inline]
do_mount+0x1956/0x2f10 fs/namespace.c:2799
ksys_mount+0xcf/0x130 fs/namespace.c:3015
__do_sys_mount fs/namespace.c:3029 [inline]
__se_sys_mount fs/namespace.c:3026 [inline]
__x64_sys_mount+0xba/0x150 fs/namespace.c:3026
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x44bf4a
Code: 48 c7 c2 bc ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb d2 e8 a8 00 00 00 0f 1f 84 00 00 00 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4576e74078 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f4576e740d0 RCX: 000000000044bf4a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007f4576e74090
RBP: 0000000000000003 R08: 00007f4576e740d0 R09: 00007f4576e746bc
R10: 0000000000000000 R11: 0000000000000286 R12: 00007f4576e74090
R13: 0000000020000248 R14: 0000000000000005 R15: 0000000000000006
CPU: 0 PID: 8161 Comm: syz-executor899 Not tainted 4.19.190-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+0x1fc/0x2ef lib/dump_stack.c:118
panic+0x26a/0x50e kernel/panic.c:186
__warn.cold+0x20/0x5a kernel/panic.c:541
report_bug+0x262/0x2b0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
fixup_bug arch/x86/kernel/traps.c:173 [inline]
do_error_trap+0x1d7/0x310 arch/x86/kernel/traps.c:296
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1038
RIP: 0010:umount_check fs/dcache.c:1518 [inline]
RIP: 0010:umount_check.cold+0xf2/0x116 fs/dcache.c:1499
Code: f9 4d 89 f1 45 89 e0 48 89 e9 41 55 4c 89 fa 48 89 ee 48 c7 c7 c0 a3 74 88 e8 8e f0 fe ff 48 c7 c7 c0 a2 74 88 e8 82 f0 fe ff <0f> 0b 58 e9 b4 fd b4 f9 e8 e0 ab a4 f9 e9 22 ff ff ff 48 89 df e8
RSP: 0018:ffff8880af1e7a98 EFLAGS: 00010286
RAX: 0000000000000024 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff814dde61 RDI: ffffed1015e3cf45
RBP: ffff88808febda20 R08: 0000000000000024 R09: 0000000000000000
R10: 0000000000000005 R11: 0000000000000000 R12: 00000000ffffff80
R13: ffff888093888990 R14: ffffffff893f8520 R15: 0000000000000000
d_walk+0x196/0x990 fs/dcache.c:1253
do_one_tree fs/dcache.c:1525 [inline]
shrink_dcache_for_umount+0x87/0x330 fs/dcache.c:1541
generic_shutdown_super+0x68/0x370 fs/super.c:441
kill_block_super+0x97/0xf0 fs/super.c:1185
deactivate_locked_super+0x94/0x160 fs/super.c:329
mount_bdev+0x373/0x3b0 fs/super.c:1160
erofs_mount+0x8c/0xc0 drivers/staging/erofs/super.c:512
mount_fs+0xa3/0x310 fs/super.c:1261
vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961
vfs_kern_mount fs/namespace.c:951 [inline]
do_new_mount fs/namespace.c:2469 [inline]
do_mount+0x113c/0x2f10 fs/namespace.c:2799
ksys_mount+0xcf/0x130 fs/namespace.c:3015
__do_sys_mount fs/namespace.c:3029 [inline]
__se_sys_mount fs/namespace.c:3026 [inline]
__x64_sys_mount+0xba/0x150 fs/namespace.c:3026
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x44bf4a
Code: 48 c7 c2 bc ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb d2 e8 a8 00 00 00 0f 1f 84 00 00 00 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4576e74078 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f4576e740d0 RCX: 000000000044bf4a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007f4576e74090
RBP: 0000000000000003 R08: 00007f4576e740d0 R09: 00007f4576e746bc
R10: 0000000000000000 R11: 0000000000000286 R12: 00007f4576e74090
R13: 0000000020000248 R14: 0000000000000005 R15: 0000000000000006
Kernel Offset: disabled
Rebooting in 86400 seconds..


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