====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ syz.9.3652/22377 is trying to acquire lock: ffff888091895900 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:400 but task is already holding lock: ffff88801cef0188 (&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_ioctl_subvol_setflags+0x45e/0x820 fs/btrfs/ioctl.c:1409 btrfs_ioctl+0x93a/0xd00 fs/btrfs/ioctl.c:5218 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 -> #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 filldir+0x2b6/0x6c0 fs/readdir.c:295 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_getdents fs/readdir.c:326 [inline] __se_sys_getdents+0xe4/0x250 fs/readdir.c:312 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.9.3652/22377: #0: ffff88804d6e6ef8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320 fs/file.c:1255 #1: ffff88807b98cbd0 (&type->i_mutex_dir_key#4){++++}-{4:4}, at: iterate_dir+0x292/0x570 fs/readdir.c:101 #2: ffff88801cef0188 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x260/0x870 fs/kernfs/dir.c:1898 stack backtrace: CPU: 1 UID: 0 PID: 22377 Comm: syz.9.3652 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:filldir+0x2b6/0x6c0 fs/readdir.c:296 Code: 87 73 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 8b 54 24 1c <66> 89 41 10 80 e2 0f 41 89 c7 42 88 54 39 ff 49 63 ee c6 44 29 12 RSP: 0018:ffffc9000471fc58 EFLAGS: 00050283 RAX: 0000000000000020 RBX: ffffc9000471fe38 RCX: 0000200000001ff0 RDX: 0000000000000004 RSI: 0000200000001fd8 RDI: 0000200000002010 RBP: 00007ffffffff000 R08: ffff888027bc5ac7 R09: 1ffff11004f78b58 R10: dffffc0000000000 R11: ffffed1004f78b59 R12: 0000200000001fd8 R13: ffffffff8b8a4a60 R14: 0000000000000006 R15: 0000200000002010 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_getdents fs/readdir.c:326 [inline] __se_sys_getdents+0xe4/0x250 fs/readdir.c:312 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: 0033:0x7fb034f8f749 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:00007fb0331d5038 EFLAGS: 00000246 ORIG_RAX: 000000000000004e RAX: ffffffffffffffda RBX: 00007fb0351e6180 RCX: 00007fb034f8f749 RDX: 00000000000000b8 RSI: 0000200000001fc0 RDI: 0000000000000007 RBP: 00007fb035013f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fb0351e6218 R14: 00007fb0351e6180 R15: 00007fffdc2f1ed8 caif:caif_disconnect_client(): nothing to disconnect ---------------- Code disassembly (best guess): 0: 87 73 02 xchg %esi,0x2(%rbx) 3: 00 00 add %al,(%rax) 5: 0f 01 cb stac 8: 0f ae e8 lfence b: 48 8b 44 24 50 mov 0x50(%rsp),%rax 10: 49 89 44 24 08 mov %rax,0x8(%r12) 15: 48 8b 4c 24 08 mov 0x8(%rsp),%rcx 1a: 48 8b 44 24 58 mov 0x58(%rsp),%rax 1f: 48 89 01 mov %rax,(%rcx) 22: 48 8b 04 24 mov (%rsp),%rax 26: 8b 54 24 1c mov 0x1c(%rsp),%edx * 2a: 66 89 41 10 mov %ax,0x10(%rcx) <-- trapping instruction 2e: 80 e2 0f and $0xf,%dl 31: 41 89 c7 mov %eax,%r15d 34: 42 88 54 39 ff mov %dl,-0x1(%rcx,%r15,1) 39: 49 63 ee movslq %r14d,%rbp 3c: c6 .byte 0xc6 3d: 44 29 12 sub %r10d,(%rdx)