====================================================== WARNING: possible circular locking dependency detected 6.4.0-rc1-syzkaller-00012-gb104dbedbe61 #0 Not tainted ------------------------------------------------------ syz-executor.0/16512 is trying to acquire lock: ffffffff8505adf0 (cpu_hotplug_lock){++++}-{0:0}, at: cpus_read_lock+0x14/0x1c kernel/cpu.c:310 but task is already holding lock: ffffffff851b0108 (freezer_mutex){+.+.}-{3:3}, at: freezer_css_online+0x3e/0xe8 kernel/cgroup/legacy_freezer.c:111 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (freezer_mutex){+.+.}-{3:3}: lock_acquire kernel/locking/lockdep.c:5691 [inline] lock_acquire+0x276/0x588 kernel/locking/lockdep.c:5656 __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x114/0xb5c kernel/locking/mutex.c:747 mutex_lock_nested+0x14/0x1c kernel/locking/mutex.c:799 freezer_change_state kernel/cgroup/legacy_freezer.c:389 [inline] freezer_write+0xa8/0x98e kernel/cgroup/legacy_freezer.c:429 cgroup_file_write+0x1b2/0x476 kernel/cgroup/cgroup.c:4071 kernfs_fop_write_iter+0x264/0x32e fs/kernfs/file.c:334 call_write_iter include/linux/fs.h:1868 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x4a4/0x568 fs/read_write.c:584 ksys_write+0x10a/0x224 fs/read_write.c:637 __do_sys_write fs/read_write.c:649 [inline] sys_write+0x28/0x36 fs/read_write.c:646 syscall_handler+0xfa/0x148 arch/riscv/include/asm/syscall.h:90 do_trap_ecall_u+0xea/0xec arch/riscv/kernel/traps.c:279 ret_from_exception+0x0/0x64 arch/riscv/kernel/entry.S:102 -> #0 (cpu_hotplug_lock){++++}-{0:0}: check_noncircular+0x1da/0x1fa kernel/locking/lockdep.c:2188 check_prev_add kernel/locking/lockdep.c:3108 [inline] check_prevs_add kernel/locking/lockdep.c:3227 [inline] validate_chain kernel/locking/lockdep.c:3842 [inline] __lock_acquire+0x19aa/0x34a2 kernel/locking/lockdep.c:5074 lock_acquire kernel/locking/lockdep.c:5691 [inline] lock_acquire+0x276/0x588 kernel/locking/lockdep.c:5656 percpu_down_read.constprop.0+0x40/0x23a include/linux/percpu-rwsem.h:51 cpus_read_lock+0x14/0x1c kernel/cpu.c:310 static_key_slow_inc+0x1e/0x6a kernel/jump_label.c:185 freezer_css_online+0xb6/0xe8 kernel/cgroup/legacy_freezer.c:117 online_css+0x68/0x152 kernel/cgroup/cgroup.c:5491 css_create kernel/cgroup/cgroup.c:5562 [inline] cgroup_apply_control_enable+0x438/0x64e kernel/cgroup/cgroup.c:3249 cgroup_mkdir+0x384/0x85e kernel/cgroup/cgroup.c:5758 kernfs_iop_mkdir+0xc8/0xfa fs/kernfs/dir.c:1219 vfs_mkdir+0x152/0x25c fs/namei.c:4115 do_mkdirat+0x22e/0x262 fs/namei.c:4138 __do_sys_mkdirat fs/namei.c:4153 [inline] sys_mkdirat+0x88/0xb2 fs/namei.c:4151 syscall_handler+0xfa/0x148 arch/riscv/include/asm/syscall.h:90 do_trap_ecall_u+0xea/0xec arch/riscv/kernel/traps.c:279 ret_from_exception+0x0/0x64 arch/riscv/kernel/entry.S:102 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(freezer_mutex); lock(cpu_hotplug_lock); lock(freezer_mutex); rlock(cpu_hotplug_lock); *** DEADLOCK *** 4 locks held by syz-executor.0/16512: #0: ff60000012e84460 (sb_writers#9){.+.+}-{0:0}, at: __sb_start_write include/linux/fs.h:1494 [inline] #0: ff60000012e84460 (sb_writers#9){.+.+}-{0:0}, at: sb_start_write include/linux/fs.h:1569 [inline] #0: ff60000012e84460 (sb_writers#9){.+.+}-{0:0}, at: mnt_want_write+0x2c/0x78 fs/namespace.c:394 #1: ff6000001524ae98 (&type->i_mutex_dir_key#7/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:810 [inline] #1: ff6000001524ae98 (&type->i_mutex_dir_key#7/1){+.+.}-{3:3}, at: filename_create+0x15a/0x306 fs/namei.c:3884 #2: ffffffff851a4ee8 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_lock include/linux/cgroup.h:370 [inline] #2: ffffffff851a4ee8 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_kn_lock_live+0xba/0x380 kernel/cgroup/cgroup.c:1683 #3: ffffffff851b0108 (freezer_mutex){+.+.}-{3:3}, at: freezer_css_online+0x3e/0xe8 kernel/cgroup/legacy_freezer.c:111 stack backtrace: CPU: 0 PID: 16512 Comm: syz-executor.0 Not tainted 6.4.0-rc1-syzkaller-00012-gb104dbedbe61 #0 Hardware name: riscv-virtio,qemu (DT) Call Trace: [] dump_backtrace+0x2e/0x3c arch/riscv/kernel/stacktrace.c:121 [] show_stack+0x34/0x40 arch/riscv/kernel/stacktrace.c:127 [] __dump_stack lib/dump_stack.c:88 [inline] [] dump_stack_lvl+0xe0/0x14c lib/dump_stack.c:106 [] dump_stack+0x1c/0x24 lib/dump_stack.c:113 [] print_circular_bug+0x3ae/0x47c kernel/locking/lockdep.c:2066 [] check_noncircular+0x1da/0x1fa kernel/locking/lockdep.c:2188 [] check_prev_add kernel/locking/lockdep.c:3108 [inline] [] check_prevs_add kernel/locking/lockdep.c:3227 [inline] [] validate_chain kernel/locking/lockdep.c:3842 [inline] [] __lock_acquire+0x19aa/0x34a2 kernel/locking/lockdep.c:5074 [] lock_acquire kernel/locking/lockdep.c:5691 [inline] [] lock_acquire+0x276/0x588 kernel/locking/lockdep.c:5656 [] percpu_down_read.constprop.0+0x40/0x23a include/linux/percpu-rwsem.h:51 [] cpus_read_lock+0x14/0x1c kernel/cpu.c:310 [] static_key_slow_inc+0x1e/0x6a kernel/jump_label.c:185 [] freezer_css_online+0xb6/0xe8 kernel/cgroup/legacy_freezer.c:117 [] online_css+0x68/0x152 kernel/cgroup/cgroup.c:5491 [] css_create kernel/cgroup/cgroup.c:5562 [inline] [] cgroup_apply_control_enable+0x438/0x64e kernel/cgroup/cgroup.c:3249 [] cgroup_mkdir+0x384/0x85e kernel/cgroup/cgroup.c:5758 [] kernfs_iop_mkdir+0xc8/0xfa fs/kernfs/dir.c:1219 [] vfs_mkdir+0x152/0x25c fs/namei.c:4115 [] do_mkdirat+0x22e/0x262 fs/namei.c:4138 [] __do_sys_mkdirat fs/namei.c:4153 [inline] [] sys_mkdirat+0x88/0xb2 fs/namei.c:4151 [] syscall_handler+0xfa/0x148 arch/riscv/include/asm/syscall.h:90 [] do_trap_ecall_u+0xea/0xec arch/riscv/kernel/traps.c:279 [] ret_from_exception+0x0/0x64 arch/riscv/kernel/entry.S:102