loop3: detected capacity change from 0 to 256 /dev/loop3: Can't open blockdev ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.3.820/8233 is trying to acquire lock: ffff888079862428 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock+0x1c/0x50 include/linux/mmap_lock.h:117 but task is already holding lock: ffff888049a13438 (&type->i_mutex_dir_key#3){++++}-{3:3}, at: iterate_dir+0x10d/0x560 fs/readdir.c:55 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&type->i_mutex_dir_key#3){++++}-{3:3}: down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498 inode_lock_shared include/linux/fs.h:797 [inline] lookup_slow+0x46/0x70 fs/namei.c:1687 walk_component+0x319/0x460 fs/namei.c:1984 lookup_last fs/namei.c:2439 [inline] path_lookupat+0x169/0x440 fs/namei.c:2463 filename_lookup+0x214/0x540 fs/namei.c:2492 kern_path+0x37/0x190 fs/namei.c:2590 lookup_bdev+0xc5/0x280 block/bdev.c:982 device_matched fs/btrfs/volumes.c:568 [inline] btrfs_free_stale_devices+0x6ec/0xa90 fs/btrfs/volumes.c:608 btrfs_forget_devices+0x52/0x80 fs/btrfs/volumes.c:1431 btrfs_control_ioctl+0x10a/0x220 fs/btrfs/super.c:2450 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 -> #2 (&fs_devs->device_list_mutex){+.+.}-{3:3}: __mutex_lock_common+0x1e3/0x2400 kernel/locking/mutex.c:596 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743 insert_dev_extents fs/btrfs/block-group.c:2399 [inline] btrfs_create_pending_block_groups+0x4da/0xec0 fs/btrfs/block-group.c:2449 __btrfs_end_transaction+0x154/0x650 fs/btrfs/transaction.c:1016 flush_space+0x43c/0xc70 fs/btrfs/space-info.c:674 btrfs_async_reclaim_data_space+0x113/0x440 fs/btrfs/space-info.c:1169 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457 kthread+0x436/0x520 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 -> #1 (sb_internal#3){.+.+}-{0:0}: percpu_down_read include/linux/percpu-rwsem.h:51 [inline] __sb_start_write include/linux/fs.h:1811 [inline] sb_start_intwrite include/linux/fs.h:1928 [inline] start_transaction+0x5bc/0x1130 fs/btrfs/transaction.c:680 btrfs_dirty_inode+0xc5/0x1c0 fs/btrfs/inode.c:6451 inode_update_time fs/inode.c:1893 [inline] touch_atime+0x2f8/0x640 fs/inode.c:1966 file_accessed include/linux/fs.h:2522 [inline] btrfs_file_mmap+0xc1/0x120 fs/btrfs/file.c:2449 call_mmap include/linux/fs.h:2178 [inline] mmap_file+0x5d/0xb0 mm/util.c:1092 __mmap_region mm/mmap.c:1796 [inline] mmap_region+0xf88/0x1650 mm/mmap.c:2933 do_mmap+0x819/0xe90 mm/mmap.c:1586 vm_mmap_pgoff+0x1c1/0x2d0 mm/util.c:551 ksys_mmap_pgoff+0x54b/0x790 mm/mmap.c:1635 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 -> #0 (&mm->mmap_lock){++++}-{3:3}: check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2c42/0x7d10 kernel/locking/lockdep.c:5012 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498 mmap_read_lock+0x1c/0x50 include/linux/mmap_lock.h:117 do_user_addr_fault+0xc35/0xc80 arch/x86/mm/fault.c:1308 handle_page_fault arch/x86/mm/fault.c:1445 [inline] exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1501 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606 user_access_begin arch/x86/include/asm/uaccess.h:576 [inline] filldir64+0x30a/0x6f0 fs/readdir.c:331 dir_emit_dot include/linux/fs.h:3718 [inline] dir_emit_dots include/linux/fs.h:3729 [inline] dcache_readdir+0x173/0x7c0 fs/libfs.c:196 iterate_dir+0x218/0x560 fs/readdir.c:-1 __do_sys_getdents64 fs/readdir.c:369 [inline] __se_sys_getdents64+0xf2/0x270 fs/readdir.c:354 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 other info that might help us debug this: Chain exists of: &mm->mmap_lock --> &fs_devs->device_list_mutex --> &type->i_mutex_dir_key#3 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&type->i_mutex_dir_key#3); lock(&fs_devs->device_list_mutex); lock(&type->i_mutex_dir_key#3); lock(&mm->mmap_lock); *** DEADLOCK *** 2 locks held by syz.3.820/8233: #0: ffff8880187f1770 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2bf/0x370 fs/file.c:1056 #1: ffff888049a13438 (&type->i_mutex_dir_key#3){++++}-{3:3}, at: iterate_dir+0x10d/0x560 fs/readdir.c:55 stack backtrace: CPU: 1 PID: 8233 Comm: syz.3.820 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2133 check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2c42/0x7d10 kernel/locking/lockdep.c:5012 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498 mmap_read_lock+0x1c/0x50 include/linux/mmap_lock.h:117 do_user_addr_fault+0xc35/0xc80 arch/x86/mm/fault.c:1308 handle_page_fault arch/x86/mm/fault.c:1445 [inline] exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1501 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606 RIP: 0010:filldir64+0x30a/0x6f0 fs/readdir.c:335 Code: 73 ab ff 4c 01 fd 0f 82 3f 02 00 00 48 b8 00 f0 ff ff ff 7f 00 00 48 39 c5 0f 87 2c 02 00 00 0f 01 cb 0f ae e8 48 8b 44 24 60 <49> 89 47 08 48 8b 04 24 48 8b 4c 24 18 48 8b 54 24 58 48 bd 00 00 RSP: 0018:ffffc9000312fcb0 EFLAGS: 00050283 RAX: 0000000000000000 RBX: ffffc9000312fe70 RCX: ffff888029788000 RDX: 0000000000000002 RSI: 0000200000001098 RDI: 00007ffffffff000 RBP: 0000200000001098 R08: 00000000000000aa R09: 0000000000000004 R10: 0000000000000002 R11: 0000000000000002 R12: 0000200000001098 R13: ffffffff8a371500 R14: 0000000000000001 R15: 0000200000001080 dir_emit_dot include/linux/fs.h:3718 [inline] dir_emit_dots include/linux/fs.h:3729 [inline] dcache_readdir+0x173/0x7c0 fs/libfs.c:196 iterate_dir+0x218/0x560 fs/readdir.c:-1 __do_sys_getdents64 fs/readdir.c:369 [inline] __se_sys_getdents64+0xf2/0x270 fs/readdir.c:354 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 RIP: 0033:0x7f13dbe2aeb9 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:00007f13da086028 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9 RAX: ffffffffffffffda RBX: 00007f13dc0a5fa0 RCX: 00007f13dbe2aeb9 RDX: 000000000000004f RSI: 0000200000001080 RDI: 0000000000000004 RBP: 00007f13dbe98c1f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f13dc0a6038 R14: 00007f13dc0a5fa0 R15: 00007ffea3e551f8 ---------------- Code disassembly (best guess): 0: 73 ab jae 0xffffffad 2: ff 4c 01 fd decl -0x3(%rcx,%rax,1) 6: 0f 82 3f 02 00 00 jb 0x24b c: 48 b8 00 f0 ff ff ff movabs $0x7ffffffff000,%rax 13: 7f 00 00 16: 48 39 c5 cmp %rax,%rbp 19: 0f 87 2c 02 00 00 ja 0x24b 1f: 0f 01 cb stac 22: 0f ae e8 lfence 25: 48 8b 44 24 60 mov 0x60(%rsp),%rax * 2a: 49 89 47 08 mov %rax,0x8(%r15) <-- trapping instruction 2e: 48 8b 04 24 mov (%rsp),%rax 32: 48 8b 4c 24 18 mov 0x18(%rsp),%rcx 37: 48 8b 54 24 58 mov 0x58(%rsp),%rdx 3c: 48 rex.W 3d: bd .byte 0xbd