====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ syz.8.1395/12863 is trying to acquire lock: ffff88802840d900 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:400 but task is already holding lock: ffff888140450988 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x260/0x870 fs/kernfs/dir.c:1898 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&root->kernfs_rwsem){++++}-{4:4}: down_write+0x96/0x1f0 kernel/locking/rwsem.c:1590 kernfs_add_one+0x41/0x5c0 fs/kernfs/dir.c:796 kernfs_create_dir_ns+0xde/0x130 fs/kernfs/dir.c:1098 sysfs_create_dir_ns+0x123/0x280 fs/sysfs/dir.c:59 create_dir lib/kobject.c:73 [inline] kobject_add_internal+0x6ab/0xcc0 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:2643 btrfs_quota_enable+0x25d/0x2920 fs/btrfs/qgroup.c:1034 btrfs_ioctl_quota_ctl+0x183/0x1c0 fs/btrfs/ioctl.c:3613 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:776 btrfs_quota_enable+0x29c/0x2920 fs/btrfs/qgroup.c:1063 btrfs_ioctl_quota_ctl+0x183/0x1c0 fs/btrfs/ioctl.c:3613 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (btrfs_trans_num_extwriters){++++}-{0:0}: join_transaction+0x1a4/0xd60 fs/btrfs/transaction.c:323 start_transaction+0x6ba/0x15f0 fs/btrfs/transaction.c:708 btrfs_create_common+0x146/0x2f0 fs/btrfs/inode.c:6928 lookup_open fs/namei.c:4446 [inline] open_last_lookups fs/namei.c:4546 [inline] path_openat+0x1387/0x3840 fs/namei.c:4790 do_filp_open+0x1fa/0x410 fs/namei.c:4820 do_sys_openat2+0x121/0x200 fs/open.c:1391 do_sys_open fs/open.c:1397 [inline] __do_sys_openat fs/open.c:1413 [inline] __se_sys_openat fs/open.c:1408 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1408 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (btrfs_trans_num_writers){++++}-{0:0}: __lock_release kernel/locking/lockdep.c:5574 [inline] lock_release+0x19a/0x3b0 kernel/locking/lockdep.c:5889 percpu_up_read include/linux/percpu-rwsem.h:112 [inline] __sb_end_write include/linux/fs/super.h:14 [inline] sb_end_intwrite+0x26/0x1c0 include/linux/fs/super.h:101 __btrfs_end_transaction+0x248/0x640 fs/btrfs/transaction.c:1084 btrfs_dirty_inode+0x14c/0x190 fs/btrfs/inode.c:6423 touch_atime+0x2f8/0x6b0 fs/inode.c:2259 file_accessed include/linux/fs.h:2261 [inline] btrfs_file_mmap_prepare+0x172/0x1f0 fs/btrfs/file.c:2050 vfs_mmap_prepare include/linux/fs.h:2073 [inline] call_mmap_prepare mm/vma.c:2633 [inline] __mmap_region mm/vma.c:2729 [inline] mmap_region+0xb29/0x1d10 mm/vma.c:2823 do_mmap+0xc45/0x10d0 mm/mmap.c:558 vm_mmap_pgoff+0x2a6/0x4d0 mm/util.c:581 ksys_mmap_pgoff+0x51f/0x760 mm/mmap.c:604 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #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 kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868 down_read_killable+0x50/0x350 kernel/locking/rwsem.c:1560 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:400 get_mmap_lock_carefully mm/mmap_lock.c:399 [inline] lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:450 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+0x71/0xd0 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:3533 [inline] kernfs_fop_readdir+0x537/0x870 fs/kernfs/dir.c:1915 iterate_dir+0x399/0x570 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+0xec/0xf80 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.8.1395/12863: #0: ffff88807c65f7b8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320 fs/file.c:1255 #1: ffff8880583f4bd0 (&type->i_mutex_dir_key#6){++++}-{4:4}, at: iterate_dir+0x292/0x570 fs/readdir.c:101 #2: ffff888140450988 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x260/0x870 fs/kernfs/dir.c:1898 stack backtrace: CPU: 1 UID: 0 PID: 12863 Comm: syz.8.1395 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2043 check_noncircular+0x12e/0x150 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 kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868 down_read_killable+0x50/0x350 kernel/locking/rwsem.c:1560 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:400 get_mmap_lock_carefully mm/mmap_lock.c:399 [inline] lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:450 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+0x71/0xd0 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: 81 ff 4c 89 ff 4c 89 e6 e8 d0 bf 81 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:ffffc90004a37c58 EFLAGS: 00050287 RAX: 000000007a6614a8 RBX: ffffc90004a37e38 RCX: ffff888025ef1e40 RDX: 0000000000000002 RSI: 0000000000000000 RDI: 0000000000000028 RBP: 00007ffffffff000 R08: 0000000000000147 R09: 0000000000000008 R10: dffffc0000000000 R11: ffffffff823efad0 R12: 0000000000000000 R13: ffff888028acd0e0 R14: 000000000000000f R15: 0000000000000028 dir_emit include/linux/fs.h:3533 [inline] kernfs_fop_readdir+0x537/0x870 fs/kernfs/dir.c:1915 iterate_dir+0x399/0x570 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+0xec/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f02eff8f749 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:00007f02f0dc2038 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9 RAX: ffffffffffffffda RBX: 00007f02f01e5fa0 RCX: 00007f02eff8f749 RDX: 0000000000000045 RSI: 0000000000000000 RDI: 0000000000000006 RBP: 00007f02f0013f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f02f01e6038 R14: 00007f02f01e5fa0 R15: 00007fff36c643b8 ---------------- Code disassembly (best guess): 0: 81 ff 4c 89 ff 4c cmp $0x4cff894c,%edi 6: 89 e6 mov %esp,%esi 8: e8 d0 bf 81 ff call 0xff81bfdd 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