possible deadlock in btrfs_del_qgroup_relation

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=174e295b880000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=2bb578566e511ab3a203
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/98c0bdb4abb3/disk-3f8a27f9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ea228ff02669/vmlinux-3f8a27f9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2bb578...@syzkaller.appspotmail.com

BTRFS error (device loop5): fail to start transaction for status update: -28
======================================================
WARNING: possible circular locking dependency detected
4.19.211-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.5/11493 is trying to acquire lock:
00000000e249b4dc (&fs_info->qgroup_ioctl_lock){+.+.}, at: btrfs_del_qgroup_relation+0x45/0x70 fs/btrfs/qgroup.c:1366

but task is already holding lock:
00000000419774e6 (sb_internal#3){.+.+}, at: sb_start_intwrite include/linux/fs.h:1626 [inline]
00000000419774e6 (sb_internal#3){.+.+}, at: start_transaction+0xa37/0xf90 fs/btrfs/transaction.c:528

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (sb_internal#3){.+.+}:
sb_start_intwrite include/linux/fs.h:1626 [inline]
start_transaction+0xa37/0xf90 fs/btrfs/transaction.c:528
btrfs_quota_enable+0x169/0x10b0 fs/btrfs/qgroup.c:905
btrfs_ioctl_quota_ctl fs/btrfs/ioctl.c:5233 [inline]
btrfs_ioctl+0x622c/0x76d0 fs/btrfs/ioctl.c:6021
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
__do_sys_ioctl fs/ioctl.c:712 [inline]
__se_sys_ioctl fs/ioctl.c:710 [inline]
__x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (&fs_info->qgroup_ioctl_lock){+.+.}:
__mutex_lock_common kernel/locking/mutex.c:937 [inline]
__mutex_lock+0xd7/0x1190 kernel/locking/mutex.c:1078
btrfs_del_qgroup_relation+0x45/0x70 fs/btrfs/qgroup.c:1366
btrfs_ioctl_qgroup_assign fs/btrfs/ioctl.c:5282 [inline]
btrfs_ioctl+0x6004/0x76d0 fs/btrfs/ioctl.c:6023
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
__do_sys_ioctl fs/ioctl.c:712 [inline]
__se_sys_ioctl fs/ioctl.c:710 [inline]
__x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
BTRFS warning (device <unknown>): duplicate device /dev/loop0 devid 1 generation 8 scanned by syz-executor.0 (11551)
entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(sb_internal#3);
lock(&fs_info->qgroup_ioctl_lock);
lock(sb_internal#3);
lock(&fs_info->qgroup_ioctl_lock);

*** DEADLOCK ***

2 locks held by syz-executor.5/11493:
#0: 000000000a633dae (sb_writers#18){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline]
#0: 000000000a633dae (sb_writers#18){.+.+}, at: mnt_want_write_file+0x63/0x1d0 fs/namespace.c:418
#1: 00000000419774e6 (sb_internal#3){.+.+}, at: sb_start_intwrite include/linux/fs.h:1626 [inline]
#1: 00000000419774e6 (sb_internal#3){.+.+}, at: start_transaction+0xa37/0xf90 fs/btrfs/transaction.c:528

stack backtrace:
CPU: 1 PID: 11493 Comm: syz-executor.5 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1222
check_prev_add kernel/locking/lockdep.c:1866 [inline]
check_prevs_add kernel/locking/lockdep.c:1979 [inline]
validate_chain kernel/locking/lockdep.c:2420 [inline]
__lock_acquire+0x30c9/0x3ff0 kernel/locking/lockdep.c:3416
lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
__mutex_lock_common kernel/locking/mutex.c:937 [inline]
__mutex_lock+0xd7/0x1190 kernel/locking/mutex.c:1078
btrfs_del_qgroup_relation+0x45/0x70 fs/btrfs/qgroup.c:1366
btrfs_ioctl_qgroup_assign fs/btrfs/ioctl.c:5282 [inline]
btrfs_ioctl+0x6004/0x76d0 fs/btrfs/ioctl.c:6023
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
__do_sys_ioctl fs/ioctl.c:712 [inline]
__se_sys_ioctl fs/ioctl.c:710 [inline]
__x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f32607400d9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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:00007f325ecb2168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f326085ff80 RCX: 00007f32607400d9
RDX: 0000000020000e80 RSI: 0000000040189429 RDI: 0000000000000005
RBP: 00007f326079bae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffce9dec27f R14: 00007f325ecb2300 R15: 0000000000022000
JFS: discard option not supported on device
BTRFS info (device loop0): using free space tree
BTRFS info (device loop0): has skinny extents
BTRFS warning (device <unknown>): duplicate device /dev/loop5 devid 1 generation 8 scanned by syz-executor.5 (11646)
BTRFS warning (device <unknown>): duplicate device /dev/loop5 devid 1 generation 8 scanned by systemd-udevd (11692)
JFS: discard option not supported on device
BTRFS info (device loop5): using free space tree
BTRFS info (device loop5): has skinny extents
BTRFS warning (device <unknown>): duplicate device /dev/loop0 devid 1 generation 8 scanned by syz-executor.0 (11730)
BTRFS warning (device <unknown>): duplicate device /dev/loop0 devid 1 generation 8 scanned by systemd-udevd (11746)
BTRFS error (device loop5): fail to start transaction for status update: -28
JFS: discard option not supported on device
BTRFS info (device loop5): using free space tree
BTRFS info (device loop5): has skinny extents
BTRFS error (device loop5): fail to start transaction for status update: -28
BTRFS info (device loop0): using free space tree
BTRFS info (device loop0): has skinny extents
BTRFS info (device loop5): using free space tree
BTRFS info (device loop5): has skinny extents
BTRFS error (device loop5): fail to start transaction for status update: -28
BTRFS info (device loop5): using free space tree
BTRFS info (device loop5): has skinny extents
BTRFS warning (device loop5): qgroup rescan is already in progress
BTRFS error (device loop5): fail to start transaction for status update: -28
BTRFS info (device loop5): using free space tree
BTRFS info (device loop5): has skinny extents
BTRFS warning (device <unknown>): duplicate device /dev/loop0 devid 1 generation 8 scanned by syz-executor.0 (12046)
BTRFS warning (device <unknown>): duplicate device /dev/loop0 devid 1 generation 8 scanned by systemd-udevd (12090)
BTRFS error (device loop5): fail to start transaction for status update: -28
BTRFS info (device loop5): using free space tree
BTRFS info (device loop5): has skinny extents
BTRFS warning (device <unknown>): duplicate device /dev/loop0 devid 1 generation 8 scanned by syz-executor.0 (12129)
BTRFS warning (device <unknown>): duplicate device /dev/loop0 devid 1 generation 8 scanned by systemd-udevd (12163)
BTRFS error (device loop5): fail to start transaction for status update: -28
BTRFS info (device loop0): using free space tree
BTRFS info (device loop0): has skinny extents
BTRFS info (device loop5): using free space tree
BTRFS info (device loop5): has skinny extents
BTRFS error (device loop5): fail to start transaction for status update: -28
BTRFS info (device loop0): using free space tree
BTRFS info (device loop0): has skinny extents
BTRFS info (device loop5): using free space tree
BTRFS info (device loop5): has skinny extents
BTRFS info (device loop5): Snapshot src from another FS
BTRFS error (device loop5): fail to start transaction for status update: -28
BTRFS info (device loop0): using free space tree
BTRFS warning (device <unknown>): duplicate device /dev/loop5 devid 1 generation 8 scanned by syz-executor.5 (12387)
BTRFS info (device loop0): has skinny extents
BTRFS warning (device <unknown>): duplicate device /dev/loop5 devid 1 generation 8 scanned by systemd-udevd (12433)
BTRFS info (device loop0): using free space tree
BTRFS info (device loop0): has skinny extents
BTRFS info (device loop5): using free space tree
BTRFS info (device loop5): has skinny extents
BTRFS error (device loop5): fail to start transaction for status update: -28
BTRFS info (device loop0): using free space tree
BTRFS info (device loop0): has skinny extents
BTRFS info (device loop5): using free space tree
BTRFS info (device loop5): has skinny extents
BTRFS error (device loop5): fail to start transaction for status update: -28
IPVS: ftp: loaded support on port[0] = 21
BTRFS info (device loop5): using free space tree
BTRFS warning (device <unknown>): duplicate device /dev/loop0 devid 1 generation 8 scanned by syz-executor.0 (12703)
BTRFS info (device loop5): has skinny extents
BTRFS warning (device <unknown>): duplicate device /dev/loop0 devid 1 generation 8 scanned by systemd-udevd (12743)
BTRFS error (device loop5): fail to start transaction for status update: -28
BTRFS info (device loop0): using free space tree
BTRFS info (device loop0): has skinny extents
BTRFS info (device loop5): using free space tree
BTRFS info (device loop5): has skinny extents
BTRFS error (device loop5): fail to start transaction for status update: -28
BTRFS info (device loop5): 4 enospc errors during balance


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y

console output: https://syzkaller.appspot.com/x/log.txt?x=122dfdad880000

kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=2bb578566e511ab3a203
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=178acf4b880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10a29ed3880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/98c0bdb4abb3/disk-3f8a27f9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ea228ff02669/vmlinux-3f8a27f9.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/13cdf02d36b9/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2bb578...@syzkaller.appspotmail.com

BTRFS: device fsid 24c7a497-3402-47dd-bef8-82358f5f30e0 devid 1 transid 8 /dev/loop0

BTRFS info (device loop0): using free space tree
BTRFS info (device loop0): has skinny extents

======================================================
WARNING: possible circular locking dependency detected
4.19.211-syzkaller #0 Not tainted
------------------------------------------------------

syz-executor313/8100 is trying to acquire lock:
000000000d7bde88 (&fs_info->qgroup_ioctl_lock){+.+.}, at: btrfs_del_qgroup_relation+0x45/0x70 fs/btrfs/qgroup.c:1366

but task is already holding lock:

000000001146e189 (sb_internal#2){.+.+}, at: sb_start_intwrite include/linux/fs.h:1626 [inline]
000000001146e189 (sb_internal#2){.+.+}, at: start_transaction+0xa37/0xf90 fs/btrfs/transaction.c:528

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (sb_internal#2){.+.+}:

entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----

lock(sb_internal#2);
lock(&fs_info->qgroup_ioctl_lock);
lock(sb_internal#2);

lock(&fs_info->qgroup_ioctl_lock);

*** DEADLOCK ***

2 locks held by syz-executor313/8100:
#0: 000000009d93883e (sb_writers#11){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline]
#0: 000000009d93883e (sb_writers#11){.+.+}, at: mnt_want_write_file+0x63/0x1d0 fs/namespace.c:418
#1: 000000001146e189 (sb_internal#2){.+.+}, at: sb_start_intwrite include/linux/fs.h:1626 [inline]
#1: 000000001146e189 (sb_internal#2){.+.+}, at: start_transaction+0xa37/0xf90 fs/btrfs/transaction.c:528

stack backtrace:
CPU: 0 PID: 8100 Comm: syz-executor313 Not tainted 4.19.211-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1222
check_prev_add kernel/locking/lockdep.c:1866 [inline]
check_prevs_add kernel/locking/lockdep.c:1979 [inline]
validate_chain kernel/locking/lockdep.c:2420 [inline]
__lock_acquire+0x30c9/0x3ff0 kernel/locking/lockdep.c:3416
lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
__mutex_lock_common kernel/locking/mutex.c:937 [inline]
__mutex_lock+0xd7/0x1190 kernel/locking/mutex.c:1078
btrfs_del_qgroup_relation+0x45/0x70 fs/btrfs/qgroup.c:1366
btrfs_ioctl_qgroup_assign fs/btrfs/ioctl.c:5282 [inline]
btrfs_ioctl+0x6004/0x76d0 fs/btrfs/ioctl.c:6023
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
__do_sys_ioctl fs/ioctl.c:712 [inline]
__se_sys_ioctl fs/ioctl.c:710 [inline]
__x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

RIP: 0033:0x7f26b4e08af9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 14 00 00 90 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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe1000e338 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 00007f26b4e08af9