====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.3.497/9422 is trying to acquire lock: ffff88803cfa5030 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:400 but task is already holding lock: ffff88813fe76238 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x267/0x870 fs/kernfs/dir.c:1898 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #5 (&root->kernfs_rwsem){++++}-{4:4}: down_write+0x3a/0x50 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+0x12f/0x2a0 fs/sysfs/dir.c:59 create_dir lib/kobject.c:73 [inline] kobject_add_internal+0x631/0xd10 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:2697 btrfs_quota_enable+0x281/0x2940 fs/btrfs/qgroup.c:1002 btrfs_ioctl_quota_ctl+0x186/0x1c0 fs/btrfs/ioctl.c:3613 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #4 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552 btrfs_quota_enable+0x2c3/0x2940 fs/btrfs/qgroup.c:1031 btrfs_ioctl_quota_ctl+0x186/0x1c0 fs/btrfs/ioctl.c:3613 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (btrfs_trans_num_extwriters){++++}-{0:0}: join_transaction+0x1a4/0xc90 fs/btrfs/transaction.c:323 start_transaction+0x6b9/0x15f0 fs/btrfs/transaction.c:708 btrfs_rebuild_free_space_tree+0xbb/0x6e0 fs/btrfs/free-space-tree.c:1330 btrfs_start_pre_rw_mount+0x12ed/0x1c50 fs/btrfs/disk-io.c:3053 open_ctree+0x2b76/0x3da0 fs/btrfs/disk-io.c:3604 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+0x1061/0x1920 fs/btrfs/super.c:2121 vfs_get_tree+0x92/0x2a0 fs/super.c:1751 fc_mount fs/namespace.c:1199 [inline] do_new_mount_fc fs/namespace.c:3636 [inline] do_new_mount+0x329/0xa50 fs/namespace.c:3712 do_mount fs/namespace.c:4035 [inline] __do_sys_mount fs/namespace.c:4224 [inline] __se_sys_mount+0x31d/0x420 fs/namespace.c:4201 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (btrfs_trans_num_writers){++++}-{0:0}: __lock_release kernel/locking/lockdep.c:5574 [inline] lock_release+0x199/0x3a0 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:6369 inode_update_time fs/inode.c:2170 [inline] file_update_time_flags+0x38d/0x4e0 fs/inode.c:2398 btrfs_page_mkwrite+0x5df/0x1b10 fs/btrfs/file.c:1916 do_page_mkwrite+0x150/0x310 mm/memory.c:3528 wp_page_shared mm/memory.c:3929 [inline] do_wp_page+0x260c/0x4930 mm/memory.c:4148 handle_pte_fault mm/memory.c:6289 [inline] __handle_mm_fault mm/memory.c:6411 [inline] handle_mm_fault+0x9f5/0x13c0 mm/memory.c:6580 do_user_addr_fault+0xa73/0x1360 arch/x86/mm/fault.c:1336 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 -> #1 (sb_pagefaults#4){.+.+}-{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+0x329/0x1b10 fs/btrfs/file.c:1875 do_page_mkwrite+0x150/0x310 mm/memory.c:3528 do_shared_fault mm/memory.c:5831 [inline] do_fault mm/memory.c:5893 [inline] do_pte_missing+0x78b/0x27a0 mm/memory.c:4401 handle_pte_fault mm/memory.c:6273 [inline] __handle_mm_fault mm/memory.c:6411 [inline] handle_mm_fault+0xd0a/0x13c0 mm/memory.c:6580 do_user_addr_fault+0x75b/0x1360 arch/x86/mm/fault.c:1387 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 rep_movs_alternative+0x4a/0x90 arch/x86/lib/copy_user_64.S:68 copy_user_generic arch/x86/include/asm/uaccess_64.h:126 [inline] raw_copy_to_user arch/x86/include/asm/uaccess_64.h:147 [inline] copy_to_user_iter lib/iov_iter.c:25 [inline] iterate_ubuf include/linux/iov_iter.h:30 [inline] iterate_and_advance2 include/linux/iov_iter.h:302 [inline] iterate_and_advance include/linux/iov_iter.h:330 [inline] _copy_to_iter+0x255/0x17d0 lib/iov_iter.c:197 copy_page_to_iter+0x10c/0x1c0 lib/iov_iter.c:374 copy_folio_to_iter include/linux/uio.h:204 [inline] filemap_read+0x814/0x1240 mm/filemap.c:2851 new_sync_read fs/read_write.c:491 [inline] vfs_read+0x58b/0xa70 fs/read_write.c:572 ksys_read+0x156/0x270 fs/read_write.c:715 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x330 kernel/locking/lockdep.c:5868 down_read_killable+0xa4/0x220 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+0x2a0/0x2f0 mm/mmap_lock.c:450 do_user_addr_fault+0x330/0x1360 arch/x86/mm/fault.c:1359 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 filldir64+0x2cd/0x670 fs/readdir.c:-1 dir_emit include/linux/fs.h:3527 [inline] kernfs_fop_readdir+0x53a/0x870 fs/kernfs/dir.c:1915 iterate_dir+0x3a5/0x580 fs/readdir.c:108 __do_sys_getdents64 fs/readdir.c:410 [inline] __se_sys_getdents64+0xf1/0x280 fs/readdir.c:396 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 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.3.497/9422: #0: ffff888032dda128 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1255 #1: ffff88805bf0ce78 (&type->i_mutex_dir_key#6){++++}-{4:4}, at: iterate_dir+0x29e/0x580 fs/readdir.c:101 #2: ffff88813fe76238 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x267/0x870 fs/kernfs/dir.c:1898 stack backtrace: CPU: 0 UID: 0 PID: 9422 Comm: syz.3.497 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 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+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+0x106/0x330 kernel/locking/lockdep.c:5868 down_read_killable+0xa4/0x220 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+0x2a0/0x2f0 mm/mmap_lock.c:450 do_user_addr_fault+0x330/0x1360 arch/x86/mm/fault.c:1359 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 RIP: 0010:filldir64+0x2cd/0x670 fs/readdir.c:381 Code: 4c 24 08 48 8b 44 24 58 48 89 01 48 8b 04 24 8b 54 24 14 49 bc 00 00 00 00 00 fc ff df 66 89 41 10 80 e2 0f 88 51 12 49 63 ee 44 29 13 00 4c 8d 79 13 bf 07 00 00 00 44 89 f6 e8 8d 7b 8a ff RSP: 0018:ffffc90005f6fc58 EFLAGS: 00050202 RAX: 0000000000000028 RBX: ffffc90005f6fe38 RCX: 0000200000001fe8 RDX: 0000000000000008 RSI: 0000200000001fc0 RDI: 0000200000002010 RBP: 000000000000000e R08: 0000000000000000 R09: 0000000000000000 R10: dffffc0000000000 R11: ffffed1005ec9001 R12: dffffc0000000000 R13: ffff88802ff81c40 R14: 000000000000000e R15: 0000200000002010 dir_emit include/linux/fs.h:3527 [inline] kernfs_fop_readdir+0x53a/0x870 fs/kernfs/dir.c:1915 iterate_dir+0x3a5/0x580 fs/readdir.c:108 __do_sys_getdents64 fs/readdir.c:410 [inline] __se_sys_getdents64+0xf1/0x280 fs/readdir.c:396 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f3666a8acb9 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:00007f3664ce6028 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9 RAX: ffffffffffffffda RBX: 00007f3666d05fa0 RCX: 00007f3666a8acb9 RDX: 0000000000001017 RSI: 0000200000001d80 RDI: 0000000000000004 RBP: 00007f3666af8bf7 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f3666d06038 R14: 00007f3666d05fa0 R15: 00007ffe0356fb38 ---------------- Code disassembly (best guess): 0: 4c 24 08 rex.WR and $0x8,%al 3: 48 8b 44 24 58 mov 0x58(%rsp),%rax 8: 48 89 01 mov %rax,(%rcx) b: 48 8b 04 24 mov (%rsp),%rax f: 8b 54 24 14 mov 0x14(%rsp),%edx 13: 49 bc 00 00 00 00 00 movabs $0xdffffc0000000000,%r12 1a: fc ff df 1d: 66 89 41 10 mov %ax,0x10(%rcx) 21: 80 e2 0f and $0xf,%dl 24: 88 51 12 mov %dl,0x12(%rcx) 27: 49 63 ee movslq %r14d,%rbp * 2a: c6 44 29 13 00 movb $0x0,0x13(%rcx,%rbp,1) <-- trapping instruction 2f: 4c 8d 79 13 lea 0x13(%rcx),%r15 33: bf 07 00 00 00 mov $0x7,%edi 38: 44 89 f6 mov %r14d,%esi 3b: e8 8d 7b 8a ff call 0xff8a7bcd