====================================================== WARNING: possible circular locking dependency detected 6.15.0-rc4-syzkaller-00021-gca91b9500108 #0 Not tainted ------------------------------------------------------ syz.0.617/10906 is trying to acquire lock: ffff88807ee4efe0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:193 but task is already holding lock: ffff88801aef5148 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x264/0x870 fs/kernfs/dir.c:1890 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:5866 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:1091 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+0xb80/0x1350 fs/btrfs/block-group.c:2803 __btrfs_end_transaction+0x140/0x640 fs/btrfs/transaction.c:1070 btrfs_create_common+0x19a/0x230 fs/btrfs/inode.c:6655 lookup_open fs/namei.c:3701 [inline] open_last_lookups fs/namei.c:3800 [inline] path_openat+0x14f1/0x3830 fs/namei.c:4036 do_filp_open+0x1fa/0x410 fs/namei.c:4066 do_sys_openat2+0x121/0x1c0 fs/open.c:1429 do_sys_open fs/open.c:1444 [inline] __do_sys_openat fs/open.c:1460 [inline] __se_sys_openat fs/open.c:1455 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1455 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf6/0x210 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:5866 join_transaction+0x1a4/0xd70 fs/btrfs/transaction.c:321 start_transaction+0x6ae/0x1620 fs/btrfs/transaction.c:705 btrfs_rebuild_free_space_tree+0xb1/0x4e0 fs/btrfs/free-space-tree.c:1317 btrfs_start_pre_rw_mount+0xd76/0x1180 fs/btrfs/disk-io.c:3074 open_ctree+0x2075/0x2800 fs/btrfs/disk-io.c:3614 btrfs_fill_super+0x19d/0x2e0 fs/btrfs/super.c:972 btrfs_get_tree_super fs/btrfs/super.c:1897 [inline] btrfs_get_tree+0x107c/0x1620 fs/btrfs/super.c:2092 vfs_get_tree+0x8f/0x2b0 fs/super.c:1759 fc_mount+0x1c/0xb0 fs/namespace.c:1293 btrfs_get_tree_subvol fs/btrfs/super.c:2050 [inline] btrfs_get_tree+0x67d/0x1620 fs/btrfs/super.c:2093 vfs_get_tree+0x8f/0x2b0 fs/super.c:1759 do_new_mount+0x24a/0xa40 fs/namespace.c:3884 do_mount fs/namespace.c:4224 [inline] __do_sys_mount fs/namespace.c:4435 [inline] __se_sys_mount+0x317/0x410 fs/namespace.c:4412 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf6/0x210 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:5383 __lock_release kernel/locking/lockdep.c:5572 [inline] lock_release+0x1b4/0x3e0 kernel/locking/lockdep.c:5887 percpu_up_read include/linux/percpu-rwsem.h:100 [inline] __sb_end_write include/linux/fs.h:1778 [inline] sb_end_intwrite+0x26/0x1c0 include/linux/fs.h:1895 __btrfs_end_transaction+0x248/0x640 fs/btrfs/transaction.c:1075 btrfs_dirty_inode+0x14c/0x190 fs/btrfs/inode.c:6140 inode_update_time fs/inode.c:2076 [inline] touch_atime+0x2f6/0x6d0 fs/inode.c:2149 file_accessed include/linux/fs.h:2599 [inline] btrfs_file_mmap+0xbf/0x120 fs/btrfs/file.c:1938 call_mmap include/linux/fs.h:2243 [inline] mmap_file mm/internal.h:167 [inline] __mmap_new_file_vma mm/vma.c:2353 [inline] __mmap_new_vma mm/vma.c:2417 [inline] __mmap_region mm/vma.c:2519 [inline] mmap_region+0x103b/0x1e50 mm/vma.c:2597 do_mmap+0xc68/0x1100 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+0xf6/0x210 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:3166 [inline] check_prevs_add kernel/locking/lockdep.c:3285 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909 __lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866 down_read_killable+0x50/0x350 kernel/locking/rwsem.c:1547 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:193 get_mmap_lock_carefully mm/memory.c:6355 [inline] lock_mm_and_find_vma+0x2a8/0x300 mm/memory.c:6406 do_user_addr_fault+0x331/0x1390 arch/x86/mm/fault.c:1360 handle_page_fault arch/x86/mm/fault.c:1480 [inline] exc_page_fault+0x68/0x110 arch/x86/mm/fault.c:1538 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623 filldir64+0x2b3/0x690 fs/readdir.c:371 dir_emit include/linux/fs.h:3861 [inline] kernfs_fop_readdir+0x534/0x870 fs/kernfs/dir.c:1907 iterate_dir+0x5ac/0x770 fs/readdir.c:108 __do_sys_getdents64 fs/readdir.c:403 [inline] __se_sys_getdents64+0xe4/0x260 fs/readdir.c:389 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf6/0x210 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.0.617/10906: #0: ffff888032822638 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320 fs/file.c:1213 #1: ffff88807dac6988 (&type->i_mutex_dir_key#6){++++}-{4:4}, at: iterate_dir+0x49f/0x770 fs/readdir.c:101 #2: ffff88801aef5148 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x264/0x870 fs/kernfs/dir.c:1890 stack backtrace: CPU: 1 UID: 0 PID: 10906 Comm: syz.0.617 Not tainted 6.15.0-rc4-syzkaller-00021-gca91b9500108 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2079 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2211 check_prev_add kernel/locking/lockdep.c:3166 [inline] check_prevs_add kernel/locking/lockdep.c:3285 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909 __lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866 down_read_killable+0x50/0x350 kernel/locking/rwsem.c:1547 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:193 get_mmap_lock_carefully mm/memory.c:6355 [inline] lock_mm_and_find_vma+0x2a8/0x300 mm/memory.c:6406 do_user_addr_fault+0x331/0x1390 arch/x86/mm/fault.c:1360 handle_page_fault arch/x86/mm/fault.c:1480 [inline] exc_page_fault+0x68/0x110 arch/x86/mm/fault.c:1538 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623 RIP: 0010:filldir64+0x2b3/0x690 fs/readdir.c:372 Code: 87 4c 02 00 00 0f 01 cb 0f ae e8 48 8b 44 24 60 49 89 46 08 48 8b 4c 24 38 48 8b 44 24 58 48 89 01 48 8b 44 24 10 8b 54 24 24 <66> 89 41 10 88 51 12 4c 63 f5 42 c6 44 31 13 00 4c 8d 61 13 bf 07 RSP: 0018:ffffc9000b8e7c68 EFLAGS: 00050287 RAX: 0000000000000030 RBX: ffffc9000b8e7e50 RCX: 0000200000002ff8 RDX: 0000000000000008 RSI: 0000200000002fd8 RDI: 0000200000003028 RBP: 0000000000000016 R08: ffff88802f4b3c07 R09: 1ffff11005e96780 R10: dffffc0000000000 R11: ffffed1005e96781 R12: 0000200000003028 R13: ffff8880309ad340 R14: 0000200000002fd8 R15: 00007ffffffff000 dir_emit include/linux/fs.h:3861 [inline] kernfs_fop_readdir+0x534/0x870 fs/kernfs/dir.c:1907 iterate_dir+0x5ac/0x770 fs/readdir.c:108 __do_sys_getdents64 fs/readdir.c:403 [inline] __se_sys_getdents64+0xe4/0x260 fs/readdir.c:389 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f7449d8e969 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:00007f744ab60038 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9 RAX: ffffffffffffffda RBX: 00007f7449fb5fa0 RCX: 00007f7449d8e969 RDX: 0000000000001002 RSI: 0000200000002f40 RDI: 0000000000000004 RBP: 00007f7449e10ab1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f7449fb5fa0 R15: 00007fff25b82748 ---------------- Code disassembly (best guess): 0: 87 4c 02 00 xchg %ecx,0x0(%rdx,%rax,1) 4: 00 0f add %cl,(%rdi) 6: 01 cb add %ecx,%ebx 8: 0f ae e8 lfence b: 48 8b 44 24 60 mov 0x60(%rsp),%rax 10: 49 89 46 08 mov %rax,0x8(%r14) 14: 48 8b 4c 24 38 mov 0x38(%rsp),%rcx 19: 48 8b 44 24 58 mov 0x58(%rsp),%rax 1e: 48 89 01 mov %rax,(%rcx) 21: 48 8b 44 24 10 mov 0x10(%rsp),%rax 26: 8b 54 24 24 mov 0x24(%rsp),%edx * 2a: 66 89 41 10 mov %ax,0x10(%rcx) <-- trapping instruction 2e: 88 51 12 mov %dl,0x12(%rcx) 31: 4c 63 f5 movslq %ebp,%r14 34: 42 c6 44 31 13 00 movb $0x0,0x13(%rcx,%r14,1) 3a: 4c 8d 61 13 lea 0x13(%rcx),%r12 3e: bf .byte 0xbf 3f: 07 (bad)