====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ syz.2.5310/1625 is trying to acquire lock: ffff888036a5cfb8 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:601 but task is already holding lock: ffff88801c2b4180 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x272/0x8d0 fs/kernfs/dir.c:1955 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #6 (&root->kernfs_rwsem){++++}-{4:4}: down_write+0x96/0x200 kernel/locking/rwsem.c:1625 kernfs_add_one+0x41/0x5c0 fs/kernfs/dir.c:809 kernfs_create_dir_ns+0xde/0x130 fs/kernfs/dir.c:1111 sysfs_create_dir_ns+0x12f/0x2a0 fs/sysfs/dir.c:59 create_dir lib/kobject.c:73 [inline] kobject_add_internal+0x62b/0xd00 lib/kobject.c:240 kobject_add_varg lib/kobject.c:374 [inline] kobject_init_and_add+0x12b/0x1a0 lib/kobject.c:457 btrfs_sysfs_add_qgroups+0x116/0x2e0 fs/btrfs/sysfs.c:2604 btrfs_quota_enable+0x282/0x2850 fs/btrfs/qgroup.c:1034 btrfs_ioctl_quota_ctl+0x183/0x1c0 fs/btrfs/ioctl.c:3540 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+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #5 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:632 [inline] __mutex_lock+0x19e/0x1420 kernel/locking/mutex.c:794 btrfs_quota_enable+0x2c6/0x2850 fs/btrfs/qgroup.c:1063 btrfs_ioctl_quota_ctl+0x183/0x1c0 fs/btrfs/ioctl.c:3540 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+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #4 (btrfs_trans_num_extwriters){++++}-{0:0}: join_transaction+0x1a4/0xd60 fs/btrfs/transaction.c:324 start_transaction+0xb0d/0x1790 fs/btrfs/transaction.c:719 btrfs_rebuild_free_space_tree+0xbb/0x6e0 fs/btrfs/free-space-tree.c:1335 btrfs_start_pre_rw_mount+0x1529/0x1f20 fs/btrfs/disk-io.c:3060 open_ctree+0x2e04/0x4220 fs/btrfs/disk-io.c:3657 btrfs_fill_super fs/btrfs/super.c:981 [inline] btrfs_get_tree_super fs/btrfs/super.c:1944 [inline] btrfs_get_tree_subvol fs/btrfs/super.c:2087 [inline] btrfs_get_tree+0x1061/0x1910 fs/btrfs/super.c:2121 vfs_get_tree+0x92/0x2a0 fs/super.c:1754 fc_mount fs/namespace.c:1193 [inline] do_new_mount_fc fs/namespace.c:3764 [inline] do_new_mount+0x341/0xd30 fs/namespace.c:3840 do_mount fs/namespace.c:4173 [inline] __do_sys_mount fs/namespace.c:4372 [inline] __se_sys_mount+0x31d/0x420 fs/namespace.c:4349 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (btrfs_trans_num_writers){++++}-{0:0}: __lock_release kernel/locking/lockdep.c:5574 [inline] lock_release+0x199/0x3c0 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:1096 btrfs_dirty_inode+0x14c/0x190 fs/btrfs/inode.c:6451 file_update_time_flags+0x2cf/0x4a0 fs/inode.c:2426 btrfs_page_mkwrite+0x607/0x1a00 fs/btrfs/file.c:1914 do_page_mkwrite+0x14d/0x310 mm/memory.c:3668 wp_page_shared mm/memory.c:4069 [inline] do_wp_page+0x19ba/0x4c20 mm/memory.c:4288 handle_pte_fault mm/memory.c:6471 [inline] __handle_mm_fault mm/memory.c:6593 [inline] handle_mm_fault+0x151d/0x3170 mm/memory.c:6762 do_user_addr_fault+0xa73/0x1340 arch/x86/mm/fault.c:1334 handle_page_fault arch/x86/mm/fault.c:1474 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 -> #2 (sb_pagefaults#3){.+.+}-{0:0}: 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/super.h:19 [inline] sb_start_pagefault include/linux/fs/super.h:159 [inline] btrfs_page_mkwrite+0x351/0x1a00 fs/btrfs/file.c:1873 do_page_mkwrite+0x14d/0x310 mm/memory.c:3668 wp_page_shared mm/memory.c:4069 [inline] do_wp_page+0x19ba/0x4c20 mm/memory.c:4288 handle_pte_fault mm/memory.c:6471 [inline] __handle_mm_fault mm/memory.c:6593 [inline] handle_mm_fault+0x151d/0x3170 mm/memory.c:6762 do_user_addr_fault+0xa73/0x1340 arch/x86/mm/fault.c:1334 handle_page_fault arch/x86/mm/fault.c:1474 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 -> #1 (vm_lock){++++}-{0:0}: __vma_start_exclude_readers+0x28a/0x940 mm/mmap_lock.c:125 __vma_start_write+0xdc/0x290 mm/mmap_lock.c:148 vma_start_write include/linux/mmap_lock.h:303 [inline] mprotect_fixup+0x67e/0xae0 mm/mprotect.c:771 setup_arg_pages+0x664/0xbd0 fs/exec.c:670 load_elf_binary+0xc5e/0x2980 fs/binfmt_elf.c:1028 search_binary_handler fs/exec.c:1675 [inline] exec_binprm fs/exec.c:1707 [inline] bprm_execve+0x956/0x1450 fs/exec.c:1759 kernel_execve+0x844/0x930 fs/exec.c:1957 try_to_run_init_process+0x13/0x60 init/main.c:1514 kernel_init+0xad/0x1d0 init/main.c:1642 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 down_read_killable+0x50/0x340 kernel/locking/rwsem.c:1593 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:601 get_mmap_lock_carefully mm/mmap_lock.c:450 [inline] lock_mm_and_find_vma+0x2d7/0x340 mm/mmap_lock.c:501 do_user_addr_fault+0x330/0x1340 arch/x86/mm/fault.c:1357 handle_page_fault arch/x86/mm/fault.c:1474 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 filldir+0x2bf/0x690 fs/readdir.c:297 dir_emit include/linux/fs.h:3572 [inline] kernfs_fop_readdir+0x57b/0x8d0 fs/kernfs/dir.c:1972 iterate_dir+0x399/0x570 fs/readdir.c:108 __do_sys_getdents fs/readdir.c:327 [inline] __se_sys_getdents+0xf1/0x270 fs/readdir.c:312 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/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.2.5310/1625: #0: ffff8880384df5f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320 fs/file.c:1261 #1: ffff88807aed2d20 (&type->i_mutex_dir_key#6){++++}-{4:4}, at: iterate_dir+0x292/0x570 fs/readdir.c:101 #2: ffff88801c2b4180 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x272/0x8d0 fs/kernfs/dir.c:1955 stack backtrace: CPU: 1 UID: 0 PID: 1625 Comm: syz.2.5310 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 down_read_killable+0x50/0x340 kernel/locking/rwsem.c:1593 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:601 get_mmap_lock_carefully mm/mmap_lock.c:450 [inline] lock_mm_and_find_vma+0x2d7/0x340 mm/mmap_lock.c:501 do_user_addr_fault+0x330/0x1340 arch/x86/mm/fault.c:1357 handle_page_fault arch/x86/mm/fault.c:1474 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 RIP: 0010:filldir+0x2bf/0x690 fs/readdir.c:297 Code: 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 00 4c 8d 61 12 bf 07 00 00 00 RSP: 0018:ffffc90004ecfc40 EFLAGS: 00050202 RAX: 0000000000000020 RBX: ffffc90004ecfe38 RCX: 0000200000001fe8 RDX: 0000000000000008 RSI: 0000200000001fc0 RDI: 0000200000002008 RBP: 00007ffffffff000 R08: ffff888035b15b87 R09: 1ffff11006b62b70 R10: dffffc0000000000 R11: ffffed1006b62b71 R12: 0000200000001fc0 R13: ffff88802168c6c0 R14: 000000000000000b R15: 0000000000000020 dir_emit include/linux/fs.h:3572 [inline] kernfs_fop_readdir+0x57b/0x8d0 fs/kernfs/dir.c:1972 iterate_dir+0x399/0x570 fs/readdir.c:108 __do_sys_getdents fs/readdir.c:327 [inline] __se_sys_getdents+0xf1/0x270 fs/readdir.c:312 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fce6b39c799 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fce6c2d0028 EFLAGS: 00000246 ORIG_RAX: 000000000000004e RAX: ffffffffffffffda RBX: 00007fce6b616180 RCX: 00007fce6b39c799 RDX: 00000000000000b8 RSI: 0000200000001fc0 RDI: 0000000000000006 RBP: 00007fce6b432c99 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fce6b616218 R14: 00007fce6b616180 R15: 00007ffc78663fc8 ---------------- Code disassembly (best guess): 0: e8 48 8b 44 24 call 0x24448b4d 5: 50 push %rax 6: 49 89 44 24 08 mov %rax,0x8(%r12) b: 48 8b 4c 24 08 mov 0x8(%rsp),%rcx 10: 48 8b 44 24 58 mov 0x58(%rsp),%rax 15: 48 89 01 mov %rax,(%rcx) 18: 48 8b 04 24 mov (%rsp),%rax 1c: 8b 54 24 1c mov 0x1c(%rsp),%edx 20: 66 89 41 10 mov %ax,0x10(%rcx) 24: 80 e2 0f and $0xf,%dl 27: 41 89 c7 mov %eax,%r15d * 2a: 42 88 54 39 ff mov %dl,-0x1(%rcx,%r15,1) <-- trapping instruction 2f: 49 63 ee movslq %r14d,%rbp 32: c6 44 29 12 00 movb $0x0,0x12(%rcx,%rbp,1) 37: 4c 8d 61 12 lea 0x12(%rcx),%r12 3b: bf 07 00 00 00 mov $0x7,%edi