============================================ WARNING: possible recursive locking detected 5.15.0-rc7-syzkaller #0 Not tainted -------------------------------------------- syz-executor.2/2026 is trying to acquire lock: ffffffff905196f0 (&port_lock_key){-.-.}-{2:2}, at: uart_write+0x12c/0x570 drivers/tty/serial/serial_core.c:570 but task is already holding lock: ffffffff905196f0 (&port_lock_key){-.-.}-{2:2}, at: serial8250_handle_irq.part.0+0x21/0x3d0 drivers/tty/serial/8250/8250_port.c:1908 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&port_lock_key); lock(&port_lock_key); *** DEADLOCK *** May be due to missing lock nesting notation 8 locks held by syz-executor.2/2026: #0: ffffffff8ba542f0 (dup_mmap_sem){++++}-{0:0}, at: dup_mmap kernel/fork.c:498 [inline] #0: ffffffff8ba542f0 (dup_mmap_sem){++++}-{0:0}, at: dup_mm+0x108/0x13e0 kernel/fork.c:1453 #1: ffff888024aa9d28 (&mm->mmap_lock#2){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline] #1: ffff888024aa9d28 (&mm->mmap_lock#2){++++}-{3:3}, at: dup_mmap kernel/fork.c:499 [inline] #1: ffff888024aa9d28 (&mm->mmap_lock#2){++++}-{3:3}, at: dup_mm+0x12e/0x13e0 kernel/fork.c:1453 #2: ffff8880221c3228 (&mm->mmap_lock/1){+.+.}-{3:3}, at: mmap_write_lock_nested include/linux/mmap_lock.h:78 [inline] #2: ffff8880221c3228 (&mm->mmap_lock/1){+.+.}-{3:3}, at: dup_mmap kernel/fork.c:508 [inline] #2: ffff8880221c3228 (&mm->mmap_lock/1){+.+.}-{3:3}, at: dup_mm+0x18a/0x13e0 kernel/fork.c:1453 #3: ffff8880707a8738 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #3: ffff8880707a8738 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_pte_range mm/memory.c:1021 [inline] #3: ffff8880707a8738 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_pmd_range mm/memory.c:1156 [inline] #3: ffff8880707a8738 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_pud_range mm/memory.c:1193 [inline] #3: ffff8880707a8738 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_p4d_range mm/memory.c:1217 [inline] #3: ffff8880707a8738 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_page_range+0xc16/0x4420 mm/memory.c:1290 #4: ffff888030d281f8 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_pte_range mm/memory.c:1028 [inline] #4: ffff888030d281f8 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_pmd_range mm/memory.c:1156 [inline] #4: ffff888030d281f8 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_pud_range mm/memory.c:1193 [inline] #4: ffff888030d281f8 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_p4d_range mm/memory.c:1217 [inline] #4: ffff888030d281f8 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_page_range+0xceb/0x4420 mm/memory.c:1290 #5: ffff888073c407b0 (&i->lock){-.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #5: ffff888073c407b0 (&i->lock){-.-.}-{2:2}, at: serial8250_interrupt+0x3a/0x200 drivers/tty/serial/8250/8250_core.c:116 #6: ffffffff905196f0 (&port_lock_key){-.-.}-{2:2}, at: serial8250_handle_irq.part.0+0x21/0x3d0 drivers/tty/serial/8250/8250_port.c:1908 #7: ffff88802b3d6098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x1d/0x80 drivers/tty/tty_ldisc.c:273 stack backtrace: CPU: 0 PID: 2026 Comm: syz-executor.2 Not tainted 5.15.0-rc7-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_deadlock_bug kernel/locking/lockdep.c:2944 [inline] check_deadlock kernel/locking/lockdep.c:2987 [inline] validate_chain kernel/locking/lockdep.c:3776 [inline] __lock_acquire.cold+0x149/0x3ab kernel/locking/lockdep.c:5015 lock_acquire kernel/locking/lockdep.c:5625 [inline] lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:162 uart_write+0x12c/0x570 drivers/tty/serial/serial_core.c:570 n_hdlc_send_frames+0x24b/0x490 drivers/tty/n_hdlc.c:290 tty_wakeup+0xe1/0x120 drivers/tty/tty_io.c:534 tty_port_default_wakeup+0x26/0x40 drivers/tty/tty_port.c:51 serial8250_tx_chars+0x4f3/0xad0 drivers/tty/serial/8250/8250_port.c:1845 serial8250_handle_irq.part.0+0x328/0x3d0 drivers/tty/serial/8250/8250_port.c:1932 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1905 [inline] serial8250_default_handle_irq+0xb2/0x220 drivers/tty/serial/8250/8250_port.c:1949 serial8250_interrupt+0xfd/0x200 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x303/0x8f0 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0x102/0x280 kernel/irq/handle.c:213 handle_edge_irq+0x25f/0xd00 kernel/irq/chip.c:822 generic_handle_irq_desc include/linux/irqdesc.h:158 [inline] handle_irq arch/x86/kernel/irq.c:231 [inline] __common_interrupt+0x9d/0x210 arch/x86/kernel/irq.c:250 common_interrupt+0x9f/0xd0 arch/x86/kernel/irq.c:240 asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:629 RIP: 0010:preempt_count arch/x86/include/asm/preempt.h:27 [inline] RIP: 0010:check_kcov_mode kernel/kcov.c:163 [inline] RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x60 kernel/kcov.c:197 Code: 01 f0 4d 89 03 e9 63 fd ff ff b9 ff ff ff ff ba 08 00 00 00 4d 8b 03 48 0f bd ca 49 8b 45 00 48 63 c9 e9 64 ff ff ff 0f 1f 00 <65> 8b 05 d9 02 8b 7e 89 c1 48 8b 34 24 81 e1 00 01 00 00 65 48 8b RSP: 0018:ffffc9000488f7f8 EFLAGS: 00000246 RAX: 0000000000000000 RBX: 800000003bea8007 RCX: ffff8880890c5580 RDX: 0000000000000000 RSI: ffff8880890c5580 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: ffffffff81adcfc3 R11: 0000000000000000 R12: ffffc9000488f9e8 R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000 copy_present_pte mm/memory.c:956 [inline] copy_pte_range mm/memory.c:1070 [inline] copy_pmd_range mm/memory.c:1156 [inline] copy_pud_range mm/memory.c:1193 [inline] copy_p4d_range mm/memory.c:1217 [inline] copy_page_range+0xf54/0x4420 mm/memory.c:1290 dup_mmap kernel/fork.c:610 [inline] dup_mm+0xa4e/0x13e0 kernel/fork.c:1453 copy_mm kernel/fork.c:1505 [inline] copy_process+0x6fdf/0x7590 kernel/fork.c:2194 kernel_clone+0xe7/0xac0 kernel/fork.c:2584 __do_sys_clone+0xc8/0x110 kernel/fork.c:2701 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f182eb040db Code: ed 0f 85 60 01 00 00 64 4c 8b 0c 25 10 00 00 00 45 31 c0 4d 8d 91 d0 02 00 00 31 d2 31 f6 bf 11 00 20 01 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 89 00 00 00 41 89 c5 85 c0 0f 85 90 00 00 RSP: 002b:00007ffdec7e22c0 EFLAGS: 00000246 ORIG_RAX: 0000000000000038 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f182eb040db RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011 RBP: 0000000000000001 R08: 0000000000000000 R09: 0000555556fc4400 R10: 0000555556fc46d0 R11: 0000000000000246 R12: 0000000000000001 R13: 0000000000000000 R14: 0000000000000001 R15: 00007ffdec7e23a0 ---------------- Code disassembly (best guess): 0: 01 f0 add %esi,%eax 2: 4d 89 03 mov %r8,(%r11) 5: e9 63 fd ff ff jmpq 0xfffffd6d a: b9 ff ff ff ff mov $0xffffffff,%ecx f: ba 08 00 00 00 mov $0x8,%edx 14: 4d 8b 03 mov (%r11),%r8 17: 48 0f bd ca bsr %rdx,%rcx 1b: 49 8b 45 00 mov 0x0(%r13),%rax 1f: 48 63 c9 movslq %ecx,%rcx 22: e9 64 ff ff ff jmpq 0xffffff8b 27: 0f 1f 00 nopl (%rax) * 2a: 65 8b 05 d9 02 8b 7e mov %gs:0x7e8b02d9(%rip),%eax # 0x7e8b030a <-- trapping instruction 31: 89 c1 mov %eax,%ecx 33: 48 8b 34 24 mov (%rsp),%rsi 37: 81 e1 00 01 00 00 and $0x100,%ecx 3d: 65 gs 3e: 48 rex.W 3f: 8b .byte 0x8b