syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.2271/12906 is trying to acquire lock:
ffff0000c6734618 (sb_internal#2){.+.+}-{0:0}, at: btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:830

but task is already holding lock:
ffff0000c6734520 (sb_pagefaults#2){.+.+}-{0:0}, at: do_page_mkwrite+0x138/0x2b8 mm/memory.c:3361

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #7 (sb_pagefaults#2){.+.+}-{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.h:1799 [inline]
       sb_start_pagefault include/linux/fs.h:1964 [inline]
       btrfs_page_mkwrite+0x284/0x1714 fs/btrfs/file.c:1875
       do_page_mkwrite+0x138/0x2b8 mm/memory.c:3361
       wp_page_shared mm/memory.c:3762 [inline]
       do_wp_page+0x1d34/0x4160 mm/memory.c:3981
       handle_pte_fault mm/memory.c:6068 [inline]
       __handle_mm_fault mm/memory.c:6195 [inline]
       handle_mm_fault+0x10b8/0x4d34 mm/memory.c:6364
       do_page_fault+0x410/0x13cc arch/arm64/mm/fault.c:653
       do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:929
       el0_da+0x64/0x230 arch/arm64/kernel/entry-common.c:562
       el0t_64_sync_handler+0x90/0x12c arch/arm64/kernel/entry-common.c:766
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

-> #6 (vm_lock){++++}-{0:0}:
       __vma_enter_locked+0x184/0x354 mm/mmap_lock.c:63
       __vma_start_write+0x34/0x158 mm/mmap_lock.c:87
       vma_start_write include/linux/mmap_lock.h:297 [inline]
       vma_expand+0x1c0/0x8f8 mm/vma.c:1131
       relocate_vma_down+0x234/0x400 mm/vma_exec.c:58
       setup_arg_pages+0x4b4/0x920 fs/exec.c:690
       load_elf_binary+0x8f4/0x1de4 fs/binfmt_elf.c:1013
       search_binary_handler fs/exec.c:1670 [inline]
       exec_binprm fs/exec.c:1702 [inline]
       bprm_execve+0x788/0x1104 fs/exec.c:1754
       kernel_execve+0x70c/0x7f4 fs/exec.c:1920
       run_init_process+0x1bc/0x1ec init/main.c:1390
       try_to_run_init_process+0x20/0x7c init/main.c:1397
       kernel_init+0xa8/0x1dc init/main.c:1525
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

-> #5 (&mm->mmap_lock){++++}-{4:4}:
       down_read_killable+0x60/0x32c kernel/locking/rwsem.c:1560
       mmap_read_lock_killable+0x28/0x8c include/linux/mmap_lock.h:462
       get_mmap_lock_carefully mm/mmap_lock.c:286 [inline]
       lock_mm_and_find_vma+0x2a4/0x2d8 mm/mmap_lock.c:337
       do_page_fault+0x50c/0x13cc arch/arm64/mm/fault.c:674
       do_translation_fault+0xc4/0x114 arch/arm64/mm/fault.c:789
       do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:929
       el1_abort+0x40/0x64 arch/arm64/kernel/entry-common.c:325
       el1h_64_sync_handler+0x50/0xfc arch/arm64/kernel/entry-common.c:459
       el1h_64_sync+0x6c/0x70 arch/arm64/kernel/entry.S:591
       __uaccess_mask_ptr arch/arm64/include/asm/uaccess.h:169 [inline]
       filldir64+0x2ec/0x6bc fs/readdir.c:379
       dir_emit include/linux/fs.h:3959 [inline]
       kernfs_fop_readdir+0x498/0x79c fs/kernfs/dir.c:1910
       iterate_dir+0x2dc/0x478 fs/readdir.c:108
       __do_sys_getdents64 fs/readdir.c:410 [inline]
       __se_sys_getdents64 fs/readdir.c:396 [inline]
       __arm64_sys_getdents64+0x110/0x2fc fs/readdir.c:396
       __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
       invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
       el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
       do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
       el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744
       el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

-> #4 (&root->kernfs_rwsem){++++}-{4:4}:
       down_write+0x50/0xc0 kernel/locking/rwsem.c:1590
       kernfs_add_one+0x48/0x60c fs/kernfs/dir.c:791
       kernfs_create_dir_ns+0xd4/0x12c fs/kernfs/dir.c:1093
       sysfs_create_dir_ns+0x114/0x24c fs/sysfs/dir.c:59
       create_dir lib/kobject.c:73 [inline]
       kobject_add_internal+0x5a8/0xb20 lib/kobject.c:240
       kobject_add_varg lib/kobject.c:374 [inline]
       kobject_init_and_add+0x118/0x17c lib/kobject.c:457
       btrfs_sysfs_add_qgroups+0x110/0x268 fs/btrfs/sysfs.c:2641
       btrfs_quota_enable+0x214/0x2208 fs/btrfs/qgroup.c:1022
       btrfs_ioctl_quota_ctl+0x178/0x1bc fs/btrfs/ioctl.c:3667
       btrfs_ioctl+0x86c/0xc3c fs/btrfs/ioctl.c:5318
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:598 [inline]
       __se_sys_ioctl fs/ioctl.c:584 [inline]
       __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:584
       __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
       invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
       el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
       do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
       el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744
       el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

-> #3 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}:
       __mutex_lock_common+0x1d0/0x2678 kernel/locking/mutex.c:598
       __mutex_lock kernel/locking/mutex.c:760 [inline]
       mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:812
       btrfs_quota_enable+0x250/0x2208 fs/btrfs/qgroup.c:1051
       btrfs_ioctl_quota_ctl+0x178/0x1bc fs/btrfs/ioctl.c:3667
       btrfs_ioctl+0x86c/0xc3c fs/btrfs/ioctl.c:5318
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:598 [inline]
       __se_sys_ioctl fs/ioctl.c:584 [inline]
       __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:584
       __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
       invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
       el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
       do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
       el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744
       el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

-> #2 (btrfs_trans_num_extwriters){++++}-{0:0}:
       join_transaction+0x190/0xb5c fs/btrfs/transaction.c:321
       start_transaction+0x778/0x155c fs/btrfs/transaction.c:705
       btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:816
       btrfs_rebuild_free_space_tree+0xac/0x75c fs/btrfs/free-space-tree.c:1339
       btrfs_start_pre_rw_mount+0xed8/0x1728 fs/btrfs/disk-io.c:3075
       open_ctree+0x2344/0x3238 fs/btrfs/disk-io.c:3617
       btrfs_fill_super fs/btrfs/super.c:991 [inline]
       btrfs_get_tree_super fs/btrfs/super.c:1954 [inline]
       btrfs_get_tree_subvol fs/btrfs/super.c:2091 [inline]
       btrfs_get_tree+0xd5c/0x159c fs/btrfs/super.c:2125
       vfs_get_tree+0x90/0x28c fs/super.c:1815
       do_new_mount+0x278/0x7f4 fs/namespace.c:3808
       path_mount+0x5b4/0xde0 fs/namespace.c:4123
       do_mount fs/namespace.c:4136 [inline]
       __do_sys_mount fs/namespace.c:4347 [inline]
       __se_sys_mount fs/namespace.c:4324 [inline]
       __arm64_sys_mount+0x3e8/0x468 fs/namespace.c:4324
       __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
       invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
       el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
       do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
       el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744
       el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

-> #1 (btrfs_trans_num_writers){++++}-{0:0}:
       join_transaction+0x164/0xb5c fs/btrfs/transaction.c:320
       start_transaction+0x778/0x155c fs/btrfs/transaction.c:705
       btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:816
       btrfs_rebuild_free_space_tree+0xac/0x75c fs/btrfs/free-space-tree.c:1339
       btrfs_start_pre_rw_mount+0xed8/0x1728 fs/btrfs/disk-io.c:3075
       open_ctree+0x2344/0x3238 fs/btrfs/disk-io.c:3617
       btrfs_fill_super fs/btrfs/super.c:991 [inline]
       btrfs_get_tree_super fs/btrfs/super.c:1954 [inline]
       btrfs_get_tree_subvol fs/btrfs/super.c:2091 [inline]
       btrfs_get_tree+0xd5c/0x159c fs/btrfs/super.c:2125
       vfs_get_tree+0x90/0x28c fs/super.c:1815
       do_new_mount+0x278/0x7f4 fs/namespace.c:3808
       path_mount+0x5b4/0xde0 fs/namespace.c:4123
       do_mount fs/namespace.c:4136 [inline]
       __do_sys_mount fs/namespace.c:4347 [inline]
       __se_sys_mount fs/namespace.c:4324 [inline]
       __arm64_sys_mount+0x3e8/0x468 fs/namespace.c:4324
       __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
       invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
       el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
       do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
       el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744
       el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

-> #0 (sb_internal#2){.+.+}-{0:0}:
       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+0x1774/0x30a4 kernel/locking/lockdep.c:5237
       lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5868
       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.h:1799 [inline]
       sb_start_intwrite include/linux/fs.h:1982 [inline]
       start_transaction+0x5bc/0x155c fs/btrfs/transaction.c:699
       btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:830
       btrfs_dirty_inode+0x90/0x190 fs/btrfs/inode.c:6244
       btrfs_update_time+0xa0/0xd0 fs/btrfs/inode.c:6278
       inode_update_time fs/inode.c:2075 [inline]
       __file_update_time fs/inode.c:2304 [inline]
       file_update_time+0x2a4/0x3c0 fs/inode.c:2334
       btrfs_page_mkwrite+0x580/0x1714 fs/btrfs/file.c:1916
       do_page_mkwrite+0x138/0x2b8 mm/memory.c:3361
       wp_page_shared mm/memory.c:3762 [inline]
       do_wp_page+0x1d34/0x4160 mm/memory.c:3981
       handle_pte_fault mm/memory.c:6068 [inline]
       __handle_mm_fault mm/memory.c:6195 [inline]
       handle_mm_fault+0x10b8/0x4d34 mm/memory.c:6364
       do_page_fault+0x410/0x13cc arch/arm64/mm/fault.c:653
       do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:929
       el0_da+0x64/0x230 arch/arm64/kernel/entry-common.c:562
       el0t_64_sync_handler+0x90/0x12c arch/arm64/kernel/entry-common.c:766
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

other info that might help us debug this:

Chain exists of:
  sb_internal#2 --> vm_lock --> sb_pagefaults#2

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(sb_pagefaults#2);
                               lock(vm_lock);
                               lock(sb_pagefaults#2);
  rlock(sb_internal#2);

 *** DEADLOCK ***

2 locks held by syz.1.2271/12906:
 #0: ffff0000d6226808 (vm_lock){++++}-{0:0}, at: lock_vma_under_rcu+0x170/0x37c mm/mmap_lock.c:147
 #1: ffff0000c6734520 (sb_pagefaults#2){.+.+}-{0:0}, at: do_page_mkwrite+0x138/0x2b8 mm/memory.c:3361

stack backtrace:
CPU: 1 UID: 0 PID: 12906 Comm: syz.1.2271 Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 dump_stack+0x1c/0x28 lib/dump_stack.c:129
 print_circular_bug+0x324/0x32c kernel/locking/lockdep.c:2043
 check_noncircular+0x154/0x174 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+0x1774/0x30a4 kernel/locking/lockdep.c:5237
 lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5868
 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.h:1799 [inline]
 sb_start_intwrite include/linux/fs.h:1982 [inline]
 start_transaction+0x5bc/0x155c fs/btrfs/transaction.c:699
 btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:830
 btrfs_dirty_inode+0x90/0x190 fs/btrfs/inode.c:6244
 btrfs_update_time+0xa0/0xd0 fs/btrfs/inode.c:6278
 inode_update_time fs/inode.c:2075 [inline]
 __file_update_time fs/inode.c:2304 [inline]
 file_update_time+0x2a4/0x3c0 fs/inode.c:2334
 btrfs_page_mkwrite+0x580/0x1714 fs/btrfs/file.c:1916
 do_page_mkwrite+0x138/0x2b8 mm/memory.c:3361
 wp_page_shared mm/memory.c:3762 [inline]
 do_wp_page+0x1d34/0x4160 mm/memory.c:3981
 handle_pte_fault mm/memory.c:6068 [inline]
 __handle_mm_fault mm/memory.c:6195 [inline]
 handle_mm_fault+0x10b8/0x4d34 mm/memory.c:6364
 do_page_fault+0x410/0x13cc arch/arm64/mm/fault.c:653
 do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:929
 el0_da+0x64/0x230 arch/arm64/kernel/entry-common.c:562
 el0t_64_sync_handler+0x90/0x12c arch/arm64/kernel/entry-common.c:766
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596