possible deadlock in btrfs_limit_qgroup

[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=17544cad880000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=50fadaee376ce7d97351
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+50fada...@syzkaller.appspotmail.com

BTRFS: device fsid 24c7a497-3402-47dd-bef8-82358f5f30e0 devid 1 transid 8 /dev/loop3
BTRFS info (device loop3): using free space tree
BTRFS info (device loop3): has skinny extents
======================================================
WARNING: possible circular locking dependency detected
4.19.211-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.3/10947 is trying to acquire lock:
000000004ef267c0 (&fs_info->qgroup_ioctl_lock){+.+.}, at: btrfs_limit_qgroup+0x63/0x7b0 fs/btrfs/qgroup.c:1467

but task is already holding lock:
000000006e25795a (sb_internal#2){.+.+}, at: sb_start_intwrite include/linux/fs.h:1626 [inline]
000000006e25795a (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){.+.+}:
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_limit_qgroup+0x63/0x7b0 fs/btrfs/qgroup.c:1467
btrfs_ioctl_qgroup_limit fs/btrfs/ioctl.c:5386 [inline]
btrfs_ioctl+0x3c0c/0x76d0 fs/btrfs/ioctl.c:6027
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

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-executor.3/10947:
#0: 000000001e26322a (sb_writers#19){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline]
#0: 000000001e26322a (sb_writers#19){.+.+}, at: mnt_want_write_file+0x63/0x1d0 fs/namespace.c:418
#1: 000000006e25795a (sb_internal#2){.+.+}, at: sb_start_intwrite include/linux/fs.h:1626 [inline]
#1: 000000006e25795a (sb_internal#2){.+.+}, at: start_transaction+0xa37/0xf90 fs/btrfs/transaction.c:528

stack backtrace:
CPU: 0 PID: 10947 Comm: syz-executor.3 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_limit_qgroup+0x63/0x7b0 fs/btrfs/qgroup.c:1467
btrfs_ioctl_qgroup_limit fs/btrfs/ioctl.c:5386 [inline]
btrfs_ioctl+0x3c0c/0x76d0 fs/btrfs/ioctl.c:6027
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: 0033:0x7fe2d4d3e0d9
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:00007fe2d32b0168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fe2d4e5df80 RCX: 00007fe2d4d3e0d9
RDX: 0000000020001140 RSI: 000000008030942b RDI: 0000000000000004
RBP: 00007fe2d4d99ae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc0415161f R14: 00007fe2d32b0300 R15: 0000000000022000
BTRFS error (device loop3): fail to start transaction for status update: -28
BTRFS info (device loop3): using free space tree
BTRFS info (device loop3): has skinny extents
BTRFS error (device loop3): fail to start transaction for status update: -28
BTRFS info (device loop3): using free space tree
BTRFS info (device loop3): has skinny extents
BTRFS error (device loop3): fail to start transaction for status update: -28
x_tables: duplicate underflow at hook 1
BTRFS info (device loop3): using free space tree
BTRFS info (device loop3): has skinny extents
BTRFS error (device loop3): fail to start transaction for status update: -28
audit: type=1326 audit(1669768848.613:5): auid=4294967295 uid=0 gid=0 ses=4294967295 subj==unconfined pid=11362 comm="syz-executor.5" exe="/root/syz-executor.5" sig=31 arch=c000003e syscall=202 compat=0 ip=0x7fdbfb7120d9 code=0x0
audit: type=1326 audit(1669768849.383:6): auid=4294967295 uid=0 gid=0 ses=4294967295 subj==unconfined pid=11401 comm="syz-executor.4" exe="/root/syz-executor.4" sig=31 arch=c000003e syscall=202 compat=0 ip=0x7f97d1d340d9 code=0x0
L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details.


---
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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=117a5829880000

kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=50fadaee376ce7d97351
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15a132a7880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13d5db55880000

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/8ede7592663d/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+50fada...@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-executor107/8064 is trying to acquire lock:
0000000027b11ccb (&fs_info->qgroup_ioctl_lock){+.+.}, at: btrfs_limit_qgroup+0x63/0x7b0 fs/btrfs/qgroup.c:1467

but task is already holding lock:

000000005edf660d (sb_internal#2){.+.+}, at: sb_start_intwrite include/linux/fs.h:1626 [inline]
000000005edf660d (sb_internal#2){.+.+}, at: start_transaction+0xa37/0xf90 fs/btrfs/transaction.c:528

2 locks held by syz-executor107/8064:
#0: 00000000fda95e56 (sb_writers#11){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline]
#0: 00000000fda95e56 (sb_writers#11){.+.+}, at: mnt_want_write_file+0x63/0x1d0 fs/namespace.c:418
#1: 000000005edf660d (sb_internal#2){.+.+}, at: sb_start_intwrite include/linux/fs.h:1626 [inline]
#1: 000000005edf660d (sb_internal#2){.+.+}, at: start_transaction+0xa37/0xf90 fs/btrfs/transaction.c:528

stack backtrace:
CPU: 0 PID: 8064 Comm: syz-executor107 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_limit_qgroup+0x63/0x7b0 fs/btrfs/qgroup.c:1467
btrfs_ioctl_qgroup_limit fs/btrfs/ioctl.c:5386 [inline]
btrfs_ioctl+0x3c0c/0x76d0 fs/btrfs/ioctl.c:6027
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: 0033:0x7fd45ed24859
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:00007ffdaf1c5088 EFLAGS: 00000