====================================================== WARNING: possible circular locking dependency detected 6.4.0-rc1-syzkaller-00012-g16a8829130ca #0 Not tainted ------------------------------------------------------ syz-executor.4/17783 is trying to acquire lock: ffff88814bfe80e0 (&type->s_umount_key#31){++++}-{3:3}, at: __do_sys_quotactl_fd fs/quota/quota.c:997 [inline] ffff88814bfe80e0 (&type->s_umount_key#31){++++}-{3:3}, at: __se_sys_quotactl_fd+0x278/0x440 fs/quota/quota.c:972 but task is already holding lock: ffff88814bfe8460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:394 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (sb_writers#4){.+.+}-{0:0}: lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5691 percpu_down_read include/linux/percpu-rwsem.h:51 [inline] __sb_start_write include/linux/fs.h:1494 [inline] sb_start_write include/linux/fs.h:1569 [inline] write_mmp_block+0xe5/0x930 fs/ext4/mmp.c:50 ext4_multi_mount_protect+0x35d/0x9f0 fs/ext4/mmp.c:347 __ext4_remount fs/ext4/super.c:6578 [inline] ext4_reconfigure+0x29a8/0x3280 fs/ext4/super.c:6677 reconfigure_super+0x3c9/0x7c0 fs/super.c:956 vfs_fsconfig_locked fs/fsopen.c:254 [inline] __do_sys_fsconfig fs/fsopen.c:439 [inline] __se_sys_fsconfig+0xa29/0xf70 fs/fsopen.c:314 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd -> #0 (&type->s_umount_key#31){++++}-{3:3}: check_prev_add kernel/locking/lockdep.c:3108 [inline] check_prevs_add kernel/locking/lockdep.c:3227 [inline] validate_chain+0x166b/0x58e0 kernel/locking/lockdep.c:3842 __lock_acquire+0x1295/0x2000 kernel/locking/lockdep.c:5074 lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5691 down_write+0x3a/0x50 kernel/locking/rwsem.c:1573 __do_sys_quotactl_fd fs/quota/quota.c:997 [inline] __se_sys_quotactl_fd+0x278/0x440 fs/quota/quota.c:972 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(sb_writers#4); lock(&type->s_umount_key#31); lock(sb_writers#4); lock(&type->s_umount_key#31 ); *** DEADLOCK *** 1 lock held by syz-executor.4/17783: #0: ffff88814bfe8460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:394 stack backtrace: CPU: 0 PID: 17783 Comm: syz-executor.4 Not tainted 6.4.0-rc1-syzkaller-00012-g16a8829130ca #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106 check_noncircular+0x2fe/0x3b0 kernel/locking/lockdep.c:2188 check_prev_add kernel/locking/lockdep.c:3108 [inline] check_prevs_add kernel/locking/lockdep.c:3227 [inline] validate_chain+0x166b/0x58e0 kernel/locking/lockdep.c:3842 __lock_acquire+0x1295/0x2000 kernel/locking/lockdep.c:5074 lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5691 down_write+0x3a/0x50 kernel/locking/rwsem.c:1573 __do_sys_quotactl_fd fs/quota/quota.c:997 [inline] __se_sys_quotactl_fd+0x278/0x440 fs/quota/quota.c:972 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7fc50308c169 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:00007fc501bfe168 EFLAGS: 00000246 ORIG_RAX: 00000000000001bb RAX: ffffffffffffffda RBX: 00007fc5031abf80 RCX: 00007fc50308c169 RDX: ffffffffffffffff RSI: ffffffff80000301 RDI: 0000000000000003 RBP: 00007fc5030e7ca1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fff39e9771f R14: 00007fc501bfe300 R15: 0000000000022000