syzbot

======================================================
WARNING: possible circular locking dependency detected
6.1.140-syzkaller #0 Not tainted
------------------------------------------------------
syz.4.546/7060 is trying to acquire lock:
ffff0000f102c650 (sb_internal#3){.+.+}-{0:0}, at: btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:780

but task is already holding lock:
ffff0000f102c558 (sb_pagefaults#4){.+.+}-{0:0}, at: do_page_mkwrite+0x13c/0x358 mm/memory.c:3011

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #7 (sb_pagefaults#4){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1891 [inline]
       sb_start_pagefault include/linux/fs.h:1995 [inline]
       btrfs_page_mkwrite+0x194/0xb78 fs/btrfs/inode.c:8583
       do_page_mkwrite+0x13c/0x358 mm/memory.c:3011
       do_shared_fault mm/memory.c:4696 [inline]
       do_fault mm/memory.c:4764 [inline]
       handle_pte_fault mm/memory.c:5031 [inline]
       __handle_mm_fault mm/memory.c:5173 [inline]
       handle_mm_fault+0x121c/0x2fd4 mm/memory.c:5294
       __do_page_fault arch/arm64/mm/fault.c:499 [inline]
       do_page_fault+0x310/0x99c arch/arm64/mm/fault.c:583
       do_translation_fault+0x94/0xc8 arch/arm64/mm/fault.c:667
       do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:803
       el1_abort+0x3c/0x5c arch/arm64/kernel/entry-common.c:367
       el1h_64_sync_handler+0x80/0xcc arch/arm64/kernel/entry-common.c:427
       el1h_64_sync+0x64/0x68 arch/arm64/kernel/entry.S:580
       __arch_copy_to_user+0x190/0x234 arch/arm64/lib/copy_template.S:158
       copy_page_to_iter+0x228/0x354 lib/iov_iter.c:725
       copy_folio_to_iter include/linux/uio.h:172 [inline]
       filemap_read+0x17b0/0x1fd8 mm/filemap.c:2819
       btrfs_file_read_iter+0x240/0x5d0 fs/btrfs/file.c:3840
       call_read_iter include/linux/fs.h:2259 [inline]
       new_sync_read fs/read_write.c:389 [inline]
       vfs_read+0x5ac/0x7c4 fs/read_write.c:470
       ksys_read+0x120/0x210 fs/read_write.c:613
       __do_sys_read fs/read_write.c:623 [inline]
       __se_sys_read fs/read_write.c:621 [inline]
       __arm64_sys_read+0x7c/0x90 fs/read_write.c:621
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #6 (&mm->mmap_lock){++++}-{3:3}:
       __might_fault+0xc4/0x124 mm/memory.c:5852
       filldir64+0x2cc/0x8fc fs/readdir.c:335
       dir_emit include/linux/fs.h:3695 [inline]
       call_filldir fs/ext4/dir.c:547 [inline]
       ext4_dx_readdir fs/ext4/dir.c:623 [inline]
       ext4_readdir+0x2758/0x2f34 fs/ext4/dir.c:145
       iterate_dir+0x1f0/0x4cc fs/readdir.c:-1
       __do_sys_getdents64 fs/readdir.c:369 [inline]
       __se_sys_getdents64 fs/readdir.c:354 [inline]
       __arm64_sys_getdents64+0x11c/0x318 fs/readdir.c:354
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #5 (&type->i_mutex_dir_key#3){++++}-{3:3}:
       down_read+0x64/0x304 kernel/locking/rwsem.c:1520
       inode_lock_shared include/linux/fs.h:768 [inline]
       lookup_slow+0x4c/0x80 fs/namei.c:1706
       walk_component+0x270/0x364 fs/namei.c:1998
       lookup_last fs/namei.c:2455 [inline]
       path_lookupat+0x13c/0x3d0 fs/namei.c:2479
       filename_lookup+0x190/0x42c fs/namei.c:2508
       kern_path+0x48/0x6c fs/namei.c:2606
       is_same_device fs/btrfs/volumes.c:695 [inline]
       device_list_add+0x1208/0x1be0 fs/btrfs/volumes.c:928
       btrfs_scan_one_device+0x364/0x570 fs/btrfs/volumes.c:1461
       btrfs_control_ioctl+0x13c/0x33c fs/btrfs/super.c:2518
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl fs/ioctl.c:856 [inline]
       __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #4 (&fs_devs->device_list_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x190/0x1f38 kernel/locking/mutex.c:603
       __mutex_lock kernel/locking/mutex.c:747 [inline]
       mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
       btrfs_run_dev_stats+0xf0/0xd00 fs/btrfs/volumes.c:8058
       commit_cowonly_roots+0x16c/0x714 fs/btrfs/transaction.c:1297
       btrfs_commit_transaction+0x10bc/0x29f0 fs/btrfs/transaction.c:2427
       btrfs_sync_fs+0x530/0xa30 fs/btrfs/super.c:1535
       sync_filesystem+0x1a0/0x218 fs/sync.c:66
       generic_shutdown_super+0x70/0x324 fs/super.c:474
       kill_anon_super+0x4c/0x80 fs/super.c:1128
       btrfs_kill_super+0x40/0x58 fs/btrfs/super.c:2448
       deactivate_locked_super+0xac/0x124 fs/super.c:332
       deactivate_super+0xe8/0x108 fs/super.c:363
       cleanup_mnt+0x37c/0x404 fs/namespace.c:1186
       __cleanup_mnt+0x20/0x30 fs/namespace.c:1193
       task_work_run+0x1ec/0x270 kernel/task_work.c:203
       resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
       do_notify_resume+0x1f70/0x2b0c arch/arm64/kernel/signal.c:1137
       prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
       exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
       el0_svc+0x98/0x138 arch/arm64/kernel/entry-common.c:638
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #3 (&fs_info->reloc_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x190/0x1f38 kernel/locking/mutex.c:603
       __mutex_lock kernel/locking/mutex.c:747 [inline]
       mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
       btrfs_record_root_in_trans fs/btrfs/transaction.c:488 [inline]
       start_transaction+0x434/0x104c fs/btrfs/transaction.c:730
       btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:766
       btrfs_create_common+0x13c/0x224 fs/btrfs/inode.c:6782
       btrfs_create+0x104/0x128 fs/btrfs/inode.c:6828
       lookup_open fs/namei.c:3482 [inline]
       open_last_lookups fs/namei.c:3550 [inline]
       path_openat+0x112c/0x2680 fs/namei.c:3780
       do_filp_open+0x174/0x344 fs/namei.c:3810
       do_sys_openat2+0x128/0x3d8 fs/open.c:1318
       do_sys_open fs/open.c:1334 [inline]
       __do_sys_openat fs/open.c:1350 [inline]
       __se_sys_openat fs/open.c:1345 [inline]
       __arm64_sys_openat+0x120/0x154 fs/open.c:1345
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #2 (btrfs_trans_num_extwriters){++++}-{0:0}:
       join_transaction+0x180/0xb6c fs/btrfs/transaction.c:303
       start_transaction+0x854/0x104c fs/btrfs/transaction.c:667
       btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:766
       btrfs_create_common+0x13c/0x224 fs/btrfs/inode.c:6782
       btrfs_create+0x104/0x128 fs/btrfs/inode.c:6828
       lookup_open fs/namei.c:3482 [inline]
       open_last_lookups fs/namei.c:3550 [inline]
       path_openat+0x112c/0x2680 fs/namei.c:3780
       do_filp_open+0x174/0x344 fs/namei.c:3810
       do_sys_openat2+0x128/0x3d8 fs/open.c:1318
       do_sys_open fs/open.c:1334 [inline]
       __do_sys_openat fs/open.c:1350 [inline]
       __se_sys_openat fs/open.c:1345 [inline]
       __arm64_sys_openat+0x120/0x154 fs/open.c:1345
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #1 (btrfs_trans_num_writers){++++}-{0:0}:
       join_transaction+0x154/0xb6c fs/btrfs/transaction.c:302
       start_transaction+0x854/0x104c fs/btrfs/transaction.c:667
       btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:766
       btrfs_create_common+0x13c/0x224 fs/btrfs/inode.c:6782
       btrfs_create+0x104/0x128 fs/btrfs/inode.c:6828
       lookup_open fs/namei.c:3482 [inline]
       open_last_lookups fs/namei.c:3550 [inline]
       path_openat+0x112c/0x2680 fs/namei.c:3780
       do_filp_open+0x174/0x344 fs/namei.c:3810
       do_sys_openat2+0x128/0x3d8 fs/open.c:1318
       do_sys_open fs/open.c:1334 [inline]
       __do_sys_openat fs/open.c:1350 [inline]
       __se_sys_openat fs/open.c:1345 [inline]
       __arm64_sys_openat+0x120/0x154 fs/open.c:1345
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #0 (sb_internal#3){.+.+}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3090 [inline]
       check_prevs_add kernel/locking/lockdep.c:3209 [inline]
       validate_chain kernel/locking/lockdep.c:3825 [inline]
       __lock_acquire+0x293c/0x6544 kernel/locking/lockdep.c:5049
       lock_acquire+0x20c/0x644 kernel/locking/lockdep.c:5662
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1891 [inline]
       sb_start_intwrite include/linux/fs.h:2013 [inline]
       start_transaction+0x5c4/0x104c fs/btrfs/transaction.c:661
       btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:780
       btrfs_dirty_inode+0xb4/0x1c0 fs/btrfs/inode.c:6274
       btrfs_update_time+0x170/0x18c fs/btrfs/inode.c:6316
       inode_update_time fs/inode.c:1958 [inline]
       __file_update_time+0xc0/0x220 fs/inode.c:2147
       file_update_time+0x26c/0x2e0 fs/inode.c:2178
       btrfs_page_mkwrite+0x394/0xb78 fs/btrfs/inode.c:8599
       do_page_mkwrite+0x13c/0x358 mm/memory.c:3011
       do_shared_fault mm/memory.c:4696 [inline]
       do_fault mm/memory.c:4764 [inline]
       handle_pte_fault mm/memory.c:5031 [inline]
       __handle_mm_fault mm/memory.c:5173 [inline]
       handle_mm_fault+0x121c/0x2fd4 mm/memory.c:5294
       __do_page_fault arch/arm64/mm/fault.c:499 [inline]
       do_page_fault+0x310/0x99c arch/arm64/mm/fault.c:583
       do_translation_fault+0x94/0xc8 arch/arm64/mm/fault.c:667
       do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:803
       el1_abort+0x3c/0x5c arch/arm64/kernel/entry-common.c:367
       el1h_64_sync_handler+0x80/0xcc arch/arm64/kernel/entry-common.c:427
       el1h_64_sync+0x64/0x68 arch/arm64/kernel/entry.S:580
       __arch_copy_to_user+0x190/0x234 arch/arm64/lib/copy_template.S:158
       copy_page_to_iter+0x228/0x354 lib/iov_iter.c:725
       copy_folio_to_iter include/linux/uio.h:172 [inline]
       filemap_read+0x17b0/0x1fd8 mm/filemap.c:2819
       btrfs_file_read_iter+0x240/0x5d0 fs/btrfs/file.c:3840
       call_read_iter include/linux/fs.h:2259 [inline]
       new_sync_read fs/read_write.c:389 [inline]
       vfs_read+0x5ac/0x7c4 fs/read_write.c:470
       ksys_read+0x120/0x210 fs/read_write.c:613
       __do_sys_read fs/read_write.c:623 [inline]
       __se_sys_read fs/read_write.c:621 [inline]
       __arm64_sys_read+0x7c/0x90 fs/read_write.c:621
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

other info that might help us debug this:

Chain exists of:
  sb_internal#3 --> &mm->mmap_lock --> sb_pagefaults#4

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sb_pagefaults#4);
                               lock(&mm->mmap_lock);
                               lock(sb_pagefaults#4);
  lock(sb_internal#3);

 *** DEADLOCK ***

3 locks held by syz.4.546/7060:
 #0: ffff0000d530e868 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x114/0x16c fs/file.c:1040
 #1: ffff0000d6147948 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:136 [inline]
 #1: ffff0000d6147948 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5322 [inline]
 #1: ffff0000d6147948 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x38/0x2e8 mm/memory.c:5384
 #2: ffff0000f102c558 (sb_pagefaults#4){.+.+}-{0:0}, at: do_page_mkwrite+0x13c/0x358 mm/memory.c:3011

stack backtrace:
CPU: 1 PID: 7060 Comm: syz.4.546 Not tainted 6.1.140-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call trace:
 dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 dump_stack+0x1c/0x5c lib/dump_stack.c:113
 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2048
 check_noncircular+0x240/0x2d4 kernel/locking/lockdep.c:2170
 check_prev_add kernel/locking/lockdep.c:3090 [inline]
 check_prevs_add kernel/locking/lockdep.c:3209 [inline]
 validate_chain kernel/locking/lockdep.c:3825 [inline]
 __lock_acquire+0x293c/0x6544 kernel/locking/lockdep.c:5049
 lock_acquire+0x20c/0x644 kernel/locking/lockdep.c:5662
 percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
 __sb_start_write include/linux/fs.h:1891 [inline]
 sb_start_intwrite include/linux/fs.h:2013 [inline]
 start_transaction+0x5c4/0x104c fs/btrfs/transaction.c:661
 btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:780
 btrfs_dirty_inode+0xb4/0x1c0 fs/btrfs/inode.c:6274
 btrfs_update_time+0x170/0x18c fs/btrfs/inode.c:6316
 inode_update_time fs/inode.c:1958 [inline]
 __file_update_time+0xc0/0x220 fs/inode.c:2147
 file_update_time+0x26c/0x2e0 fs/inode.c:2178
 btrfs_page_mkwrite+0x394/0xb78 fs/btrfs/inode.c:8599
 do_page_mkwrite+0x13c/0x358 mm/memory.c:3011
 do_shared_fault mm/memory.c:4696 [inline]
 do_fault mm/memory.c:4764 [inline]
 handle_pte_fault mm/memory.c:5031 [inline]
 __handle_mm_fault mm/memory.c:5173 [inline]
 handle_mm_fault+0x121c/0x2fd4 mm/memory.c:5294
 __do_page_fault arch/arm64/mm/fault.c:499 [inline]
 do_page_fault+0x310/0x99c arch/arm64/mm/fault.c:583
 do_translation_fault+0x94/0xc8 arch/arm64/mm/fault.c:667
 do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:803
 el1_abort+0x3c/0x5c arch/arm64/kernel/entry-common.c:367
 el1h_64_sync_handler+0x80/0xcc arch/arm64/kernel/entry-common.c:427
 el1h_64_sync+0x64/0x68 arch/arm64/kernel/entry.S:580
 __arch_copy_to_user+0x190/0x234 arch/arm64/lib/copy_template.S:158
 copy_page_to_iter+0x228/0x354 lib/iov_iter.c:725
 copy_folio_to_iter include/linux/uio.h:172 [inline]
 filemap_read+0x17b0/0x1fd8 mm/filemap.c:2819
 btrfs_file_read_iter+0x240/0x5d0 fs/btrfs/file.c:3840
 call_read_iter include/linux/fs.h:2259 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x5ac/0x7c4 fs/read_write.c:470
 ksys_read+0x120/0x210 fs/read_write.c:613
 __do_sys_read fs/read_write.c:623 [inline]
 __se_sys_read fs/read_write.c:621 [inline]
 __arm64_sys_read+0x7c/0x90 fs/read_write.c:621
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585