====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.8.216/7521 is trying to acquire lock: ffff8880212fde50 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:377 but task is already holding lock: ffff88813ff76238 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x267/0x870 fs/kernfs/dir.c:1893 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #5 (&root->kernfs_rwsem){++++}-{4:4}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 down_write+0x3a/0x50 kernel/locking/rwsem.c:1590 kernfs_add_one+0x41/0x520 fs/kernfs/dir.c:791 kernfs_create_dir_ns+0xde/0x130 fs/kernfs/dir.c:1093 sysfs_create_dir_ns+0x123/0x280 fs/sysfs/dir.c:59 create_dir lib/kobject.c:73 [inline] kobject_add_internal+0x5a5/0xb50 lib/kobject.c:240 kobject_add_varg lib/kobject.c:374 [inline] kobject_init_and_add+0x125/0x190 lib/kobject.c:457 btrfs_sysfs_add_qgroups+0x111/0x2b0 fs/btrfs/sysfs.c:2645 btrfs_quota_enable+0x25d/0x2920 fs/btrfs/qgroup.c:1022 btrfs_ioctl_quota_ctl+0x186/0x1c0 fs/btrfs/ioctl.c:3667 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #4 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/rtmutex_api.c:535 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:547 btrfs_quota_enable+0x29c/0x2920 fs/btrfs/qgroup.c:1051 btrfs_ioctl_quota_ctl+0x186/0x1c0 fs/btrfs/ioctl.c:3667 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (btrfs_trans_num_extwriters){++++}-{0:0}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 join_transaction+0x1a4/0xca0 fs/btrfs/transaction.c:321 start_transaction+0x6b6/0x1620 fs/btrfs/transaction.c:705 btrfs_rebuild_free_space_tree+0xad/0x6d0 fs/btrfs/free-space-tree.c:1340 btrfs_start_pre_rw_mount+0x128f/0x1bf0 fs/btrfs/disk-io.c:3062 open_ctree+0x2b11/0x3d20 fs/btrfs/disk-io.c:3619 btrfs_fill_super fs/btrfs/super.c:987 [inline] btrfs_get_tree_super fs/btrfs/super.c:1951 [inline] btrfs_get_tree_subvol fs/btrfs/super.c:2094 [inline] btrfs_get_tree+0x1061/0x1920 fs/btrfs/super.c:2128 vfs_get_tree+0x92/0x2b0 fs/super.c:1758 fc_mount fs/namespace.c:1199 [inline] do_new_mount_fc fs/namespace.c:3642 [inline] do_new_mount+0x302/0xa10 fs/namespace.c:3718 do_mount fs/namespace.c:4041 [inline] __do_sys_mount fs/namespace.c:4229 [inline] __se_sys_mount+0x313/0x410 fs/namespace.c:4206 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (btrfs_trans_num_writers){++++}-{0:0}: reacquire_held_locks+0x127/0x1d0 kernel/locking/lockdep.c:5385 __lock_release kernel/locking/lockdep.c:5574 [inline] lock_release+0x1b4/0x3e0 kernel/locking/lockdep.c:5889 percpu_up_read include/linux/percpu-rwsem.h:112 [inline] __sb_end_write include/linux/fs.h:1911 [inline] sb_end_intwrite+0x26/0x1c0 include/linux/fs.h:2028 __btrfs_end_transaction+0x248/0x640 fs/btrfs/transaction.c:1076 btrfs_dirty_inode+0x14c/0x190 fs/btrfs/inode.c:6286 inode_update_time fs/inode.c:2129 [inline] __file_update_time fs/inode.c:2357 [inline] file_update_time+0x34d/0x490 fs/inode.c:2387 btrfs_page_mkwrite+0x5dd/0x1a80 fs/btrfs/file.c:1915 do_page_mkwrite+0x150/0x310 mm/memory.c:3489 wp_page_shared mm/memory.c:3890 [inline] do_wp_page+0x25c8/0x4930 mm/memory.c:4109 handle_pte_fault mm/memory.c:6211 [inline] __handle_mm_fault mm/memory.c:6336 [inline] handle_mm_fault+0x97c/0x3400 mm/memory.c:6505 do_user_addr_fault+0xa7c/0x1380 arch/x86/mm/fault.c:1336 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 -> #1 (sb_pagefaults#5){.+.+}-{0:0}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline] percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline] __sb_start_write include/linux/fs.h:1916 [inline] sb_start_pagefault include/linux/fs.h:2081 [inline] btrfs_page_mkwrite+0x32c/0x1a80 fs/btrfs/file.c:1874 do_page_mkwrite+0x150/0x310 mm/memory.c:3489 do_shared_fault mm/memory.c:5792 [inline] do_fault mm/memory.c:5854 [inline] do_pte_missing mm/memory.c:4362 [inline] handle_pte_fault mm/memory.c:6195 [inline] __handle_mm_fault mm/memory.c:6336 [inline] handle_mm_fault+0x124b/0x3400 mm/memory.c:6505 do_user_addr_fault+0x764/0x1380 arch/x86/mm/fault.c:1387 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 -> #0 (&mm->mmap_lock){++++}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 down_read_killable+0x9d/0x220 kernel/locking/rwsem.c:1560 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:377 get_mmap_lock_carefully mm/mmap_lock.c:378 [inline] lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:429 do_user_addr_fault+0x331/0x1380 arch/x86/mm/fault.c:1359 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 user_access_begin arch/x86/include/asm/uaccess.h:-1 [inline] filldir64+0x29d/0x690 fs/readdir.c:373 dir_emit include/linux/fs.h:3988 [inline] kernfs_fop_readdir+0x53a/0x870 fs/kernfs/dir.c:1910 iterate_dir+0x3a5/0x580 fs/readdir.c:108 __do_sys_getdents64 fs/readdir.c:410 [inline] __se_sys_getdents64+0xe4/0x260 fs/readdir.c:396 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: &mm->mmap_lock --> &fs_info->qgroup_ioctl_lock --> &root->kernfs_rwsem Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(&root->kernfs_rwsem); lock(&fs_info->qgroup_ioctl_lock); lock(&root->kernfs_rwsem); rlock(&mm->mmap_lock); *** DEADLOCK *** 3 locks held by syz.8.216/7521: #0: ffff888029873d28 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x253/0x320 fs/file.c:1232 #1: ffff8880646d2d78 (&type->i_mutex_dir_key#6){++++}-{4:4}, at: iterate_dir+0x29e/0x580 fs/readdir.c:101 #2: ffff88813ff76238 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x267/0x870 fs/kernfs/dir.c:1893 stack backtrace: CPU: 0 UID: 0 PID: 7521 Comm: syz.8.216 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 down_read_killable+0x9d/0x220 kernel/locking/rwsem.c:1560 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:377 get_mmap_lock_carefully mm/mmap_lock.c:378 [inline] lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:429 do_user_addr_fault+0x331/0x1380 arch/x86/mm/fault.c:1359 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 RIP: 0010:filldir64+0x29d/0x690 fs/readdir.c:377 Code: 8c ff 4c 89 ff 4c 89 e6 e8 a0 68 8c ff 4d 39 e7 0f 82 5b 02 00 00 49 39 ef 0f 87 52 02 00 00 0f 01 cb 0f ae e8 48 8b 44 24 50 <49> 89 44 24 08 48 8b 4c 24 08 48 8b 44 24 58 48 89 01 48 8b 04 24 RSP: 0018:ffffc90003ad7c58 EFLAGS: 00050287 RAX: 000000007a6614a8 RBX: ffffc90003ad7e38 RCX: ffff888020b65a00 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000028 RBP: 00007ffffffff000 R08: 0000000000000000 R09: 0000000000000000 R10: dffffc0000000000 R11: ffffffff823244c0 R12: 0000000000000000 R13: ffff88802743d520 R14: 000000000000000f R15: 0000000000000028 dir_emit include/linux/fs.h:3988 [inline] kernfs_fop_readdir+0x53a/0x870 fs/kernfs/dir.c:1910 iterate_dir+0x3a5/0x580 fs/readdir.c:108 __do_sys_getdents64 fs/readdir.c:410 [inline] __se_sys_getdents64+0xe4/0x260 fs/readdir.c:396 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f0e1dbbf749 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f0e139dc038 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9 RAX: ffffffffffffffda RBX: 00007f0e1de16180 RCX: 00007f0e1dbbf749 RDX: 0000000000000045 RSI: 0000000000000000 RDI: 0000000000000005 RBP: 00007f0e1dc43f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f0e1de16218 R14: 00007f0e1de16180 R15: 00007ffc77dbce78 ---------------- Code disassembly (best guess): 0: 8c ff mov %?,%edi 2: 4c 89 ff mov %r15,%rdi 5: 4c 89 e6 mov %r12,%rsi 8: e8 a0 68 8c ff call 0xff8c68ad d: 4d 39 e7 cmp %r12,%r15 10: 0f 82 5b 02 00 00 jb 0x271 16: 49 39 ef cmp %rbp,%r15 19: 0f 87 52 02 00 00 ja 0x271 1f: 0f 01 cb stac 22: 0f ae e8 lfence 25: 48 8b 44 24 50 mov 0x50(%rsp),%rax * 2a: 49 89 44 24 08 mov %rax,0x8(%r12) <-- trapping instruction 2f: 48 8b 4c 24 08 mov 0x8(%rsp),%rcx 34: 48 8b 44 24 58 mov 0x58(%rsp),%rax 39: 48 89 01 mov %rax,(%rcx) 3c: 48 8b 04 24 mov (%rsp),%rax