syzbot

======================================================
WARNING: possible circular locking dependency detected
6.1.28-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor142/4243 is trying to acquire lock:
ffff0000d817c0e0 (&type->s_umount_key#30){++++}-{3:3}, at: __do_sys_quotactl_fd fs/quota/quota.c:999 [inline]
ffff0000d817c0e0 (&type->s_umount_key#30){++++}-{3:3}, at: __se_sys_quotactl_fd fs/quota/quota.c:972 [inline]
ffff0000d817c0e0 (&type->s_umount_key#30){++++}-{3:3}, at: __arm64_sys_quotactl_fd+0x30c/0x4a4 fs/quota/quota.c:972

but task is already holding lock:
ffff0000d817c460 (sb_writers#3){.+.+}-{0:0}, at: mnt_want_write+0x44/0x9c fs/namespace.c:393

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (sb_writers#3){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1832 [inline]
       sb_start_write include/linux/fs.h:1907 [inline]
       write_mmp_block+0x100/0xb8c fs/ext4/mmp.c:50
       ext4_multi_mount_protect+0x2e0/0x8a4 fs/ext4/mmp.c:349
       __ext4_remount fs/ext4/super.c:6530 [inline]
       ext4_reconfigure+0x218c/0x2934 fs/ext4/super.c:6629
       reconfigure_super+0x328/0x738 fs/super.c:957
       vfs_fsconfig_locked fs/fsopen.c:254 [inline]
       __do_sys_fsconfig fs/fsopen.c:439 [inline]
       __se_sys_fsconfig fs/fsopen.c:314 [inline]
       __arm64_sys_fsconfig+0xa1c/0xd18 fs/fsopen.c:314
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x64/0x218 arch/arm64/kernel/syscall.c:206
       el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581

-> #0 (&type->s_umount_key#30){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3098 [inline]
       check_prevs_add kernel/locking/lockdep.c:3217 [inline]
       validate_chain kernel/locking/lockdep.c:3832 [inline]
       __lock_acquire+0x3338/0x764c kernel/locking/lockdep.c:5056
       lock_acquire+0x26c/0x7cc kernel/locking/lockdep.c:5669
       down_read+0x5c/0x78 kernel/locking/rwsem.c:1520
       __do_sys_quotactl_fd fs/quota/quota.c:999 [inline]
       __se_sys_quotactl_fd fs/quota/quota.c:972 [inline]
       __arm64_sys_quotactl_fd+0x30c/0x4a4 fs/quota/quota.c:972
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x64/0x218 arch/arm64/kernel/syscall.c:206
       el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sb_writers#3);
                               lock(&type->s_umount_key#30);
                               lock(sb_writers#3);
  lock(&type->s_umount_key#30);

 *** DEADLOCK ***

1 lock held by syz-executor142/4243:
 #0: ffff0000d817c460 (sb_writers#3){.+.+}-{0:0}, at: mnt_want_write+0x44/0x9c fs/namespace.c:393

stack backtrace:
CPU: 0 PID: 4243 Comm: syz-executor142 Not tainted 6.1.28-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
Call trace:
 dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106
 dump_stack+0x1c/0x5c lib/dump_stack.c:113
 print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2056
 check_noncircular+0x2cc/0x378 kernel/locking/lockdep.c:2178
 check_prev_add kernel/locking/lockdep.c:3098 [inline]
 check_prevs_add kernel/locking/lockdep.c:3217 [inline]
 validate_chain kernel/locking/lockdep.c:3832 [inline]
 __lock_acquire+0x3338/0x764c kernel/locking/lockdep.c:5056
 lock_acquire+0x26c/0x7cc kernel/locking/lockdep.c:5669
 down_read+0x5c/0x78 kernel/locking/rwsem.c:1520
 __do_sys_quotactl_fd fs/quota/quota.c:999 [inline]
 __se_sys_quotactl_fd fs/quota/quota.c:972 [inline]
 __arm64_sys_quotactl_fd+0x30c/0x4a4 fs/quota/quota.c:972
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x64/0x218 arch/arm64/kernel/syscall.c:206
 el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581