syzbot

======================================================
WARNING: possible circular locking dependency detected
5.15.112-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor167/3530 is trying to acquire lock:
ffff88814a88e0e0 (&type->s_umount_key#32){++++}-{3:3}, at: __do_sys_quotactl_fd fs/quota/quota.c:998 [inline]
ffff88814a88e0e0 (&type->s_umount_key#32){++++}-{3:3}, at: __se_sys_quotactl_fd+0x24a/0x3b0 fs/quota/quota.c:971

but task is already holding lock:
ffff88814a88e460 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:377

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (sb_writers#5){.+.+}-{0:0}:
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5622
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1742 [inline]
       sb_start_write include/linux/fs.h:1812 [inline]
       write_mmp_block+0xe3/0x940 fs/ext4/mmp.c:50
       ext4_multi_mount_protect+0x54a/0x980 fs/ext4/mmp.c:351
       ext4_remount+0x2723/0x2fb0 fs/ext4/super.c:5949
       reconfigure_super+0x3c5/0x7c0 fs/super.c:916
       do_remount fs/namespace.c:2656 [inline]
       path_mount+0xceb/0x10a0 fs/namespace.c:3316
       do_mount fs/namespace.c:3337 [inline]
       __do_sys_mount fs/namespace.c:3545 [inline]
       __se_sys_mount+0x2d5/0x3c0 fs/namespace.c:3522
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x61/0xcb

-> #0 (&type->s_umount_key#32){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain+0x1646/0x58b0 kernel/locking/lockdep.c:3787
       __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5011
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5622
       down_read+0x45/0x2e0 kernel/locking/rwsem.c:1488
       __do_sys_quotactl_fd fs/quota/quota.c:998 [inline]
       __se_sys_quotactl_fd+0x24a/0x3b0 fs/quota/quota.c:971
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x61/0xcb

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sb_writers#5);
                               lock(&type->s_umount_key#32);
                               lock(sb_writers#5);
  lock(&type->s_umount_key#32);

 *** DEADLOCK ***

1 lock held by syz-executor167/3530:
 #0: ffff88814a88e460 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:377

stack backtrace:
CPU: 1 PID: 3530 Comm: syz-executor167 Not tainted 5.15.112-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/28/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 check_noncircular+0x2f8/0x3b0 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain+0x1646/0x58b0 kernel/locking/lockdep.c:3787
 __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5011
 lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5622
 down_read+0x45/0x2e0 kernel/locking/rwsem.c:1488
 __do_sys_quotactl_fd fs/quota/quota.c:998 [inline]
 __se_sys_quotactl_fd+0x24a/0x3b0 fs/quota/quota.c:971
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7fc7617654f9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 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:00007fff5de4a7b8 EFLAGS: 00000246 ORIG_RAX: 00000000000001bb
RAX: ffffffffffffffda RBX: 00000000200001c0 RCX: 00007fc7617654f9
RDX: 0000000000000000 RSI: ffffffff80000602 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000020000000 R09: 000000000000000d
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000009dbf
R13: 00007fff5de4a7e0 R14: 00007fff5de4a7cc R15: 00007fff5de4a7d0
 </TASK>