[btrfs?] possible deadlock in btrfs_add_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=1391cef0480000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=beaef9139479177cd347
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+beaef9...@syzkaller.appspotmail.com

audit: type=1800 audit(1671475619.790:624): pid=18262 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="syz-executor.5" name="bus" dev="loop5" ino=263 res=0
======================================================
WARNING: possible circular locking dependency detected
4.19.211-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.5/18262 is trying to acquire lock:
00000000a29b71a2 (&fs_info->qgroup_ioctl_lock){+.+.}, at: btrfs_add_qgroup_relation+0xa7/0x740 fs/btrfs/qgroup.c:1264

but task is already holding lock:
0000000023a92bc3 (sb_internal#3){.+.+}, at: sb_start_intwrite include/linux/fs.h:1626 [inline]
0000000023a92bc3 (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){+.+.}:
audit: type=1804 audit(1671475619.830:625): pid=18262 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=invalid_pcr cause=open_writers comm="syz-executor.5" name="/root/syzkaller-testdir2085957550/syzkaller.biS8vz/1027/file0/bus" dev="loop5" ino=263 res=1
__mutex_lock_common kernel/locking/mutex.c:937 [inline]
__mutex_lock+0xd7/0x1190 kernel/locking/mutex.c:1078
btrfs_add_qgroup_relation+0xa7/0x740 fs/btrfs/qgroup.c:1264
btrfs_ioctl_qgroup_assign fs/btrfs/ioctl.c:5280 [inline]
btrfs_ioctl+0x3a05/0x76d0 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

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.5/18262:
#0: 000000006ea56d16 (sb_writers#19){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline]
#0: 000000006ea56d16 (sb_writers#19){.+.+}, at: mnt_want_write_file+0x63/0x1d0 fs/namespace.c:418
#1: 0000000023a92bc3 (sb_internal#3){.+.+}, at: sb_start_intwrite include/linux/fs.h:1626 [inline]
#1: 0000000023a92bc3 (sb_internal#3){.+.+}, at: start_transaction+0xa37/0xf90 fs/btrfs/transaction.c:528

stack backtrace:
CPU: 1 PID: 18262 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_add_qgroup_relation+0xa7/0x740 fs/btrfs/qgroup.c:1264
btrfs_ioctl_qgroup_assign fs/btrfs/ioctl.c:5280 [inline]
btrfs_ioctl+0x3a05/0x76d0 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: 0033:0x7ff2e49250d9
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:00007ff2e2e97168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff2e4a44f80 RCX: 00007ff2e49250d9
RDX: 00000000200010c0 RSI: 0000000040189429 RDI: 0000000000000005
RBP: 00007ff2e4980ae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffe9b4edcdf R14: 00007ff2e2e97300 R15: 0000000000022000
BTRFS info (device loop5): using free space tree
BTRFS info (device loop5): has skinny extents
audit: type=1800 audit(1671475621.190:626): pid=18370 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="syz-executor.5" name="bus" dev="loop5" ino=263 res=0
audit: type=1804 audit(1671475621.210:627): pid=18370 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=invalid_pcr cause=open_writers comm="syz-executor.5" name="/root/syzkaller-testdir2085957550/syzkaller.biS8vz/1028/file0/bus" dev="loop5" ino=263 res=1
audit: type=1800 audit(1671475621.560:628): pid=18453 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="syz-executor.5" name="bus" dev="sda1" ino=15123 res=0
audit: type=1804 audit(1671475621.610:629): pid=18453 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=invalid_pcr cause=open_writers comm="syz-executor.5" name="/root/syzkaller-testdir2085957550/syzkaller.biS8vz/1029/bus" dev="sda1" ino=15123 res=1
BTRFS info (device loop5): using free space tree
BTRFS info (device loop5): has skinny extents


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.