====================================================== WARNING: possible circular locking dependency detected 6.16.0-rc6-syzkaller-00037-ge2291551827f #0 Not tainted ------------------------------------------------------ syz.2.427/8803 is trying to acquire lock: ffff8880348c01e0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:421 but task is already holding lock: ffff88801b2fd188 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x264/0x870 fs/kernfs/dir.c:1893 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&root->kernfs_rwsem){++++}-{4:4}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577 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+0x59f/0xb40 lib/kobject.c:240 kobject_add_varg lib/kobject.c:374 [inline] kobject_add+0x155/0x220 lib/kobject.c:426 btrfs_sysfs_add_block_group_type+0x262/0x460 fs/btrfs/sysfs.c:1897 btrfs_create_pending_block_groups+0xb80/0x1360 fs/btrfs/block-group.c:2803 __btrfs_end_transaction+0x140/0x640 fs/btrfs/transaction.c:1071 btrfs_inc_block_group_ro+0x641/0x6f0 fs/btrfs/block-group.c:3077 btrfs_relocate_block_group+0x47a/0xde0 fs/btrfs/relocation.c:3962 btrfs_relocate_chunk+0x12a/0x3b0 fs/btrfs/volumes.c:3437 __btrfs_balance+0x1870/0x21d0 fs/btrfs/volumes.c:4212 btrfs_balance+0xc94/0x11d0 fs/btrfs/volumes.c:4589 btrfs_ioctl_balance+0x3d3/0x610 fs/btrfs/ioctl.c:3583 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (btrfs_trans_num_extwriters){++++}-{0:0}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 join_transaction+0x1a4/0xd70 fs/btrfs/transaction.c:321 start_transaction+0x6b6/0x1620 fs/btrfs/transaction.c:705 btrfs_rebuild_free_space_tree+0xad/0x550 fs/btrfs/free-space-tree.c:1352 btrfs_start_pre_rw_mount+0xd76/0x1180 fs/btrfs/disk-io.c:3078 open_ctree+0x2078/0x2800 fs/btrfs/disk-io.c:3618 btrfs_fill_super+0x19d/0x2e0 fs/btrfs/super.c:968 btrfs_get_tree_super fs/btrfs/super.c:1893 [inline] btrfs_get_tree+0x107c/0x1630 fs/btrfs/super.c:2088 vfs_get_tree+0x92/0x2b0 fs/super.c:1804 fc_mount+0x1c/0xb0 fs/namespace.c:1290 btrfs_get_tree_subvol fs/btrfs/super.c:2046 [inline] btrfs_get_tree+0x67d/0x1630 fs/btrfs/super.c:2089 vfs_get_tree+0x92/0x2b0 fs/super.c:1804 do_new_mount+0x24a/0xa40 fs/namespace.c:3902 do_mount fs/namespace.c:4239 [inline] __do_sys_mount fs/namespace.c:4450 [inline] __se_sys_mount+0x317/0x410 fs/namespace.c:4427 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (btrfs_trans_num_writers){++++}-{0:0}: reacquire_held_locks+0x127/0x1d0 kernel/locking/lockdep.c:5388 __lock_release kernel/locking/lockdep.c:5577 [inline] lock_release+0x1b4/0x3e0 kernel/locking/lockdep.c:5892 percpu_up_read include/linux/percpu-rwsem.h:112 [inline] __sb_end_write include/linux/fs.h:1790 [inline] sb_end_intwrite+0x26/0x1c0 include/linux/fs.h:1907 __btrfs_end_transaction+0x248/0x640 fs/btrfs/transaction.c:1076 btrfs_dirty_inode+0x14c/0x190 fs/btrfs/inode.c:6239 inode_update_time fs/inode.c:2076 [inline] touch_atime+0x2f6/0x6d0 fs/inode.c:2149 file_accessed include/linux/fs.h:2652 [inline] btrfs_file_mmap+0xbb/0x120 fs/btrfs/file.c:1988 call_mmap include/linux/fs.h:2286 [inline] mmap_file mm/internal.h:167 [inline] __mmap_new_file_vma mm/vma.c:2405 [inline] __mmap_new_vma mm/vma.c:2467 [inline] __mmap_region mm/vma.c:2622 [inline] mmap_region+0x127a/0x1f30 mm/vma.c:2692 do_mmap+0xc45/0x10d0 mm/mmap.c:561 vm_mmap_pgoff+0x31b/0x4c0 mm/util.c:579 ksys_mmap_pgoff+0x51f/0x760 mm/mmap.c:607 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 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:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 down_read_killable+0x50/0x350 kernel/locking/rwsem.c:1547 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:421 get_mmap_lock_carefully mm/mmap_lock.c:197 [inline] lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:248 do_user_addr_fault+0x331/0x1390 arch/x86/mm/fault.c:1359 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623 filldir+0x2bc/0x6c0 fs/readdir.c:295 dir_emit include/linux/fs.h:3921 [inline] kernfs_fop_readdir+0x534/0x870 fs/kernfs/dir.c:1910 iterate_dir+0x5af/0x770 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+0xfa/0x3b0 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 --> btrfs_trans_num_extwriters --> &root->kernfs_rwsem Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(&root->kernfs_rwsem); lock(btrfs_trans_num_extwriters); lock(&root->kernfs_rwsem); rlock(&mm->mmap_lock); *** DEADLOCK *** 3 locks held by syz.2.427/8803: #0: ffff88802b5869b8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320 fs/file.c:1217 #1: ffff8880597bf8a0 (&type->i_mutex_dir_key#6){++++}-{4:4}, at: iterate_dir+0x49f/0x770 fs/readdir.c:101 #2: ffff88801b2fd188 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x264/0x870 fs/kernfs/dir.c:1893 stack backtrace: CPU: 1 UID: 0 PID: 8803 Comm: syz.2.427 Not tainted 6.16.0-rc6-syzkaller-00037-ge2291551827f #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 down_read_killable+0x50/0x350 kernel/locking/rwsem.c:1547 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:421 get_mmap_lock_carefully mm/mmap_lock.c:197 [inline] lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:248 do_user_addr_fault+0x331/0x1390 arch/x86/mm/fault.c:1359 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623 RIP: 0010:filldir+0x2bc/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:ffffc9000e2bfc50 EFLAGS: 00050287 RAX: 0000000000000028 RBX: ffffc9000e2bfe38 RCX: 0000200000001ff0 RDX: 0000000000000008 RSI: 0000200000001fd8 RDI: 0000200000002018 RBP: 00007ffffffff000 R08: ffff888032acda07 R09: 1ffff11006559b40 R10: dffffc0000000000 R11: ffffed1006559b41 R12: 0000200000001fd8 R13: ffff88802bbd30e0 R14: 000000000000000d R15: 0000200000002018 dir_emit include/linux/fs.h:3921 [inline] kernfs_fop_readdir+0x534/0x870 fs/kernfs/dir.c:1910 iterate_dir+0x5af/0x770 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+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fa2afb8e929 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:00007fa2ad9d5038 EFLAGS: 00000246 ORIG_RAX: 000000000000004e RAX: ffffffffffffffda RBX: 00007fa2afdb6080 RCX: 00007fa2afb8e929 RDX: 00000000000000b8 RSI: 0000200000001fc0 RDI: 0000000000000003 RBP: 00007fa2afc10ca1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000001 R14: 00007fa2afdb6080 R15: 00007ffe4faed898 ---------------- 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)