====================================================== WARNING: possible circular locking dependency detected 5.15.182-syzkaller #0 Not tainted ------------------------------------------------------ syz.4.316/5670 is trying to acquire lock: ffff8880276ac5a8 (&p->pi_lock){-.-.}-{2:2}, at: try_to_wake_up+0x5c/0x1050 kernel/sched/core.c:4030 but task is already holding lock: ffff88801fad0dd8 (&port->delta_msr_wait){-...}-{2:2}, at: __wake_up_common_lock kernel/sched/wait.c:137 [inline] ffff88801fad0dd8 (&port->delta_msr_wait){-...}-{2:2}, at: __wake_up+0xed/0x180 kernel/sched/wait.c:157 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&port->delta_msr_wait){-...}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162 __wake_up_common_lock kernel/sched/wait.c:137 [inline] __wake_up+0xed/0x180 kernel/sched/wait.c:157 serial8250_modem_status+0x1f1/0x270 drivers/tty/serial/8250/8250_port.c:1859 serial8250_handle_irq+0x438/0x610 drivers/tty/serial/8250/8250_port.c:1921 serial8250_default_handle_irq+0xb4/0x1a0 drivers/tty/serial/8250/8250_port.c:1941 serial8250_interrupt+0x9b/0x1c0 drivers/tty/serial/8250/8250_core.c:127 __handle_irq_event_percpu+0x291/0x9b0 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0xa5/0x220 kernel/irq/handle.c:213 handle_edge_irq+0x243/0xb20 kernel/irq/chip.c:819 generic_handle_irq_desc include/linux/irqdesc.h:158 [inline] handle_irq arch/x86/kernel/irq.c:233 [inline] __common_interrupt+0xd7/0x1e0 arch/x86/kernel/irq.c:252 common_interrupt+0xb0/0xd0 arch/x86/kernel/irq.c:242 asm_common_interrupt+0x22/0x40 arch/x86/include/asm/idtentry.h:667 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline] _raw_spin_unlock_irqrestore+0xa5/0x100 kernel/locking/spinlock.c:194 spin_unlock_irqrestore include/linux/spinlock.h:418 [inline] uart_update_mctrl drivers/tty/serial/serial_core.c:157 [inline] uart_tiocmset+0x22e/0x2c0 drivers/tty/serial/serial_core.c:1094 tty_tiocmset drivers/tty/tty_io.c:2592 [inline] tty_ioctl+0x9c8/0xc20 drivers/tty/tty_io.c:2785 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 -> #3 (&port_lock_key){-...}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162 serial8250_console_write+0x170/0xf80 drivers/tty/serial/8250/8250_port.c:3363 call_console_drivers kernel/printk/printk.c:-1 [inline] console_unlock+0xc86/0x1200 kernel/printk/printk.c:2744 vprintk_emit+0xc0/0x150 kernel/printk/printk.c:2274 _printk+0xcc/0x110 kernel/printk/printk.c:2299 register_console+0x682/0x960 kernel/printk/printk.c:3107 univ8250_console_init+0x41/0x50 drivers/tty/serial/8250/8250_core.c:690 console_init+0x177/0x5d0 kernel/printk/printk.c:3207 start_kernel+0x2f9/0x530 init/main.c:1076 secondary_startup_64_no_verify+0xb1/0xbb -> #2 (console_owner){-...}-{0:0}: console_lock_spinning_enable+0x51/0x60 kernel/printk/printk.c:1805 console_unlock+0x9f8/0x1200 kernel/printk/printk.c:2741 vprintk_emit+0xc0/0x150 kernel/printk/printk.c:2274 _printk+0xcc/0x110 kernel/printk/printk.c:2299 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x36d/0x4c0 lib/fault-inject.c:146 strncpy_from_user+0x32/0x360 lib/strncpy_from_user.c:118 strncpy_from_user_nofault+0x6d/0x140 mm/maccess.c:295 bpf_probe_read_user_str_common kernel/trace/bpf_trace.c:194 [inline] ____bpf_probe_read_compat_str kernel/trace/bpf_trace.c:300 [inline] bpf_probe_read_compat_str+0xdd/0x170 kernel/trace/bpf_trace.c:296 0xffffffffa00185c9 bpf_dispatcher_nop_func include/linux/bpf.h:790 [inline] __bpf_prog_run include/linux/filter.h:621 [inline] bpf_prog_run include/linux/filter.h:635 [inline] __bpf_trace_run kernel/trace/bpf_trace.c:1878 [inline] bpf_trace_run3+0x26e/0x320 kernel/trace/bpf_trace.c:1916 trace_sched_switch include/trace/events/sched.h:220 [inline] __schedule+0x1d8b/0x43b0 kernel/sched/core.c:6373 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6780 irqentry_exit+0x63/0x70 kernel/entry/common.c:432 asm_sysvec_reschedule_ipi+0x16/0x20 arch/x86/include/asm/idtentry.h:681 ____sys_sendmsg+0x3ae/0x8c0 net/socket.c:2421 ___sys_sendmsg+0x1f0/0x260 net/socket.c:2490 __sys_sendmsg net/socket.c:2519 [inline] __do_sys_sendmsg net/socket.c:2528 [inline] __se_sys_sendmsg+0x190/0x250 net/socket.c:2526 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 -> #1 (&rq->__lock){-.-.}-{2:2}: _raw_spin_lock_nested+0x2e/0x40 kernel/locking/spinlock.c:368 raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:475 raw_spin_rq_lock kernel/sched/sched.h:1326 [inline] rq_lock kernel/sched/sched.h:1621 [inline] task_fork_fair+0x5c/0x350 kernel/sched/fair.c:11499 sched_cgroup_fork+0x2c6/0x320 kernel/sched/core.c:4466 copy_process+0x22bd/0x3e60 kernel/fork.c:2319 kernel_clone+0x219/0x930 kernel/fork.c:2603 kernel_thread+0xc8/0x120 kernel/fork.c:2655 rest_init+0x21/0x330 init/main.c:706 start_kernel+0x486/0x530 init/main.c:1140 secondary_startup_64_no_verify+0xb1/0xbb -> #0 (&p->pi_lock){-.-.}-{2:2}: 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+0x2c33/0x7c60 kernel/locking/lockdep.c:5012 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162 try_to_wake_up+0x5c/0x1050 kernel/sched/core.c:4030 __wake_up_common+0x2a4/0x4e0 kernel/sched/wait.c:108 __wake_up_common_lock kernel/sched/wait.c:138 [inline] __wake_up+0x108/0x180 kernel/sched/wait.c:157 serial8250_modem_status+0x1f1/0x270 drivers/tty/serial/8250/8250_port.c:1859 serial8250_handle_irq+0x438/0x610 drivers/tty/serial/8250/8250_port.c:1921 serial8250_default_handle_irq+0xb4/0x1a0 drivers/tty/serial/8250/8250_port.c:1941 serial8250_interrupt+0x9b/0x1c0 drivers/tty/serial/8250/8250_core.c:127 __handle_irq_event_percpu+0x291/0x9b0 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0xa5/0x220 kernel/irq/handle.c:213 handle_edge_irq+0x243/0xb20 kernel/irq/chip.c:819 generic_handle_irq_desc include/linux/irqdesc.h:158 [inline] handle_irq arch/x86/kernel/irq.c:233 [inline] __common_interrupt+0xd7/0x1e0 arch/x86/kernel/irq.c:252 common_interrupt+0xb0/0xd0 arch/x86/kernel/irq.c:242 asm_common_interrupt+0x22/0x40 arch/x86/include/asm/idtentry.h:667 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline] _raw_spin_unlock_irqrestore+0xa5/0x100 kernel/locking/spinlock.c:194 spin_unlock_irqrestore include/linux/spinlock.h:418 [inline] uart_update_mctrl drivers/tty/serial/serial_core.c:157 [inline] uart_tiocmset+0x22e/0x2c0 drivers/tty/serial/serial_core.c:1094 tty_tiocmset drivers/tty/tty_io.c:2592 [inline] tty_ioctl+0x9c8/0xc20 drivers/tty/tty_io.c:2785 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 other info that might help us debug this: Chain exists of: &p->pi_lock --> &port_lock_key --> &port->delta_msr_wait Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&port->delta_msr_wait); lock(&port_lock_key); lock(&port->delta_msr_wait); lock(&p->pi_lock); *** DEADLOCK *** 4 locks held by syz.4.316/5670: #0: ffff88801fad0e90 (&port->mutex){+.+.}-{3:3}, at: uart_tiocmset+0x54/0x2c0 drivers/tty/serial/serial_core.c:1088 #1: ffff88807530a9b0 (&i->lock){-...}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #1: ffff88807530a9b0 (&i->lock){-...}-{2:2}, at: serial8250_interrupt+0x3e/0x1c0 drivers/tty/serial/8250/8250_core.c:117 #2: ffffffff963c8420 (&port_lock_key){-...}-{2:2}, at: serial8250_handle_irq+0x6c/0x610 drivers/tty/serial/8250/8250_port.c:1895 #3: ffff88801fad0dd8 (&port->delta_msr_wait){-...}-{2:2}, at: __wake_up_common_lock kernel/sched/wait.c:137 [inline] #3: ffff88801fad0dd8 (&port->delta_msr_wait){-...}-{2:2}, at: __wake_up+0xed/0x180 kernel/sched/wait.c:157 stack backtrace: CPU: 0 PID: 5670 Comm: syz.4.316 Not tainted 5.15.182-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025 Call Trace: dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106 check_noncircular+0x274/0x310 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+0x2c33/0x7c60 kernel/locking/lockdep.c:5012 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162 try_to_wake_up+0x5c/0x1050 kernel/sched/core.c:4030 __wake_up_common+0x2a4/0x4e0 kernel/sched/wait.c:108 __wake_up_common_lock kernel/sched/wait.c:138 [inline] __wake_up+0x108/0x180 kernel/sched/wait.c:157 serial8250_modem_status+0x1f1/0x270 drivers/tty/serial/8250/8250_port.c:1859 serial8250_handle_irq+0x438/0x610 drivers/tty/serial/8250/8250_port.c:1921 serial8250_default_handle_irq+0xb4/0x1a0 drivers/tty/serial/8250/8250_port.c:1941 serial8250_interrupt+0x9b/0x1c0 drivers/tty/serial/8250/8250_core.c:127 __handle_irq_event_percpu+0x291/0x9b0 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0xa5/0x220 kernel/irq/handle.c:213 handle_edge_irq+0x243/0xb20 kernel/irq/chip.c:819 generic_handle_irq_desc include/linux/irqdesc.h:158 [inline] handle_irq arch/x86/kernel/irq.c:233 [inline] __common_interrupt+0xd7/0x1e0 arch/x86/kernel/irq.c:252 common_interrupt+0xb0/0xd0 arch/x86/kernel/irq.c:242 asm_common_interrupt+0x22/0x40 arch/x86/include/asm/idtentry.h:667 RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline] RIP: 0010:_raw_spin_unlock_irqrestore+0xa5/0x100 kernel/locking/spinlock.c:194 Code: 74 05 e8 ee 4f d3 f7 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 c6 cf a6 f7 65 8b 05 67 e3 57 76 85 c0 74 3c 48 c7 04 24 0e 36 RSP: 0018:ffffc90002edfdc0 EFLAGS: 00000206 RAX: 16f889dc85884e00 RBX: 0000000000000a06 RCX: 16f889dc85884e00 RDX: dffffc0000000000 RSI: ffffffff8a0b0fc0 RDI: 0000000000000001 RBP: ffffc90002edfe50 R08: dffffc0000000000 R09: fffffbfff1ff3423 R10: fffffbfff1ff3423 R11: 1ffffffff1ff3422 R12: dffffc0000000000 R13: ffffffff963c8558 R14: ffffffff963c8408 R15: 1ffff920005dbfb8 spin_unlock_irqrestore include/linux/spinlock.h:418 [inline] uart_update_mctrl drivers/tty/serial/serial_core.c:157 [inline] uart_tiocmset+0x22e/0x2c0 drivers/tty/serial/serial_core.c:1094 tty_tiocmset drivers/tty/tty_io.c:2592 [inline] tty_ioctl+0x9c8/0xc20 drivers/tty/tty_io.c:2785 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 RIP: 0033:0x7f4cc891e969 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f4cc6765038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f4cc8b46080 RCX: 00007f4cc891e969 RDX: 0000200000000140 RSI: 0000000000005418 RDI: 000000000000000b RBP: 00007f4cc89a0ab1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000001 R14: 00007f4cc8b46080 R15: 00007ffe98dbfa88 vkms_vblank_simulate: vblank timer overrun ---------------- Code disassembly (best guess): 0: 74 05 je 0x7 2: e8 ee 4f d3 f7 call 0xf7d34ff5 7: 48 c7 44 24 20 00 00 movq $0x0,0x20(%rsp) e: 00 00 10: 9c pushf 11: 8f 44 24 20 pop 0x20(%rsp) 15: f6 44 24 21 02 testb $0x2,0x21(%rsp) 1a: 75 4b jne 0x67 1c: f7 c3 00 02 00 00 test $0x200,%ebx 22: 74 01 je 0x25 24: fb sti 25: bf 01 00 00 00 mov $0x1,%edi * 2a: e8 c6 cf a6 f7 call 0xf7a6cff5 <-- trapping instruction 2f: 65 8b 05 67 e3 57 76 mov %gs:0x7657e367(%rip),%eax # 0x7657e39d 36: 85 c0 test %eax,%eax 38: 74 3c je 0x76 3a: 48 rex.W 3b: c7 .byte 0xc7 3c: 04 24 add $0x24,%al 3e: 0e (bad) 3f: 36 ss