WARNING: possible circular locking dependency detected 6.3.0-rc7-syzkaller-00043-gaf67688dca57 #0 Not tainted ------------------------------------------------------ syz-executor.0/5338 is trying to acquire lock: ffffffff8c8e1128 (zonelist_update_seq.seqcount){...-}-{0:0}, at: __alloc_pages+0x408/0x4a0 mm/page_alloc.c:5605 but task is already holding lock: ffff88802445c158 (&port->lock){-...}-{2:2}, at: tty_insert_flip_string_and_push_buffer+0x2f/0x160 drivers/tty/tty_buffer.c:628 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&port->lock){-...}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x3d/0x60 kernel/locking/spinlock.c:162 tty_port_tty_get+0x21/0xf0 drivers/tty/tty_port.c:327 tty_port_default_wakeup+0x15/0x40 drivers/tty/tty_port.c:68 serial8250_tx_chars+0x53e/0xdf0 drivers/tty/serial/8250/8250_port.c:1865 __start_tx drivers/tty/serial/8250/8250_port.c:1582 [inline] serial8250_start_tx+0x6d5/0x850 drivers/tty/serial/8250/8250_port.c:1688 __uart_start.isra.0+0x16b/0x1b0 drivers/tty/serial/serial_core.c:141 uart_write+0x2ff/0x570 drivers/tty/serial/serial_core.c:601 process_output_block drivers/tty/n_tty.c:586 [inline] n_tty_write+0x4ce/0xfd0 drivers/tty/n_tty.c:2350 do_tty_write drivers/tty/tty_io.c:1018 [inline] file_tty_write.constprop.0+0x453/0x9c0 drivers/tty/tty_io.c:1089 redirected_tty_write+0xa5/0xc0 drivers/tty/tty_io.c:1110 call_write_iter include/linux/fs.h:1851 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x9ed/0xe10 fs/read_write.c:584 ksys_write+0x12b/0x250 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd -> #2 (&port_lock_key){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x3d/0x60 kernel/locking/spinlock.c:162 serial8250_console_write+0x4ba/0x1010 drivers/tty/serial/8250/8250_port.c:3412 console_emit_next_record kernel/printk/printk.c:2886 [inline] console_flush_all+0x49c/0xcc0 kernel/printk/printk.c:2942 console_unlock+0xb8/0x1f0 kernel/printk/printk.c:3016 vprintk_emit+0x1bd/0x600 kernel/printk/printk.c:2316 vprintk+0x84/0xa0 kernel/printk/printk_safe.c:50 _printk+0xbf/0xf0 kernel/printk/printk.c:2337 register_console+0x7ef/0x10e0 kernel/printk/printk.c:3467 univ8250_console_init+0x38/0x50 drivers/tty/serial/8250/8250_core.c:688 console_init+0xba/0x5c0 kernel/printk/printk.c:3610 start_kernel+0x273/0x4d0 init/main.c:1081 secondary_startup_64_no_verify+0xce/0xdb -> #1 (console_owner){....}-{0:0}: console_lock_spinning_enable kernel/printk/printk.c:1867 [inline] console_emit_next_record kernel/printk/printk.c:2880 [inline] console_flush_all+0x472/0xcc0 kernel/printk/printk.c:2942 console_unlock+0xb8/0x1f0 kernel/printk/printk.c:3016 vprintk_emit+0x1bd/0x600 kernel/printk/printk.c:2316 vprintk+0x84/0xa0 kernel/printk/printk_safe.c:50 _printk+0xbf/0xf0 kernel/printk/printk.c:2337 build_zonelists+0x357/0x560 mm/page_alloc.c:6543 __build_all_zonelists+0x122/0x180 mm/page_alloc.c:6656 build_all_zonelists_init+0x1c/0x190 mm/page_alloc.c:6681 build_all_zonelists+0x4a/0x150 mm/page_alloc.c:6714 start_kernel+0xb7/0x4d0 init/main.c:975 secondary_startup_64_no_verify+0xce/0xdb -> #0 (zonelist_update_seq.seqcount){...-}-{0:0}: check_prev_add kernel/locking/lockdep.c:3098 [inline] check_prevs_add kernel/locking/lockdep.c:3217 [inline] validate_chain kernel/locking/lockdep.c:3832 [inline] __lock_acquire+0x2ec7/0x5d40 kernel/locking/lockdep.c:5056 lock_acquire kernel/locking/lockdep.c:5669 [inline] lock_acquire+0x1af/0x520 kernel/locking/lockdep.c:5634 seqcount_lockdep_reader_access include/linux/seqlock.h:102 [inline] read_seqbegin include/linux/seqlock.h:836 [inline] zonelist_iter_begin mm/page_alloc.c:4765 [inline] __alloc_pages_slowpath.constprop.0+0x15a/0x2170 mm/page_alloc.c:5086 __alloc_pages+0x408/0x4a0 mm/page_alloc.c:5605 __alloc_pages_node include/linux/gfp.h:237 [inline] kmem_getpages mm/slab.c:1360 [inline] cache_grow_begin+0x9b/0x3b0 mm/slab.c:2570 cache_alloc_refill+0x27f/0x380 mm/slab.c:2943 ____cache_alloc mm/slab.c:3019 [inline] ____cache_alloc mm/slab.c:3002 [inline] __do_cache_alloc mm/slab.c:3202 [inline] slab_alloc_node mm/slab.c:3250 [inline] __kmem_cache_alloc_node+0x360/0x3f0 mm/slab.c:3541 __do_kmalloc_node mm/slab_common.c:966 [inline] __kmalloc+0x4e/0x190 mm/slab_common.c:980 kmalloc include/linux/slab.h:584 [inline] tty_buffer_alloc+0x275/0x2f0 drivers/tty/tty_buffer.c:180 __tty_buffer_request_room+0x15b/0x2d0 drivers/tty/tty_buffer.c:278 tty_insert_flip_string_fixed_flag+0x90/0x250 drivers/tty/tty_buffer.c:327 tty_insert_flip_string include/linux/tty_flip.h:41 [inline] tty_insert_flip_string_and_push_buffer+0x42/0x160 drivers/tty/tty_buffer.c:629 pty_write+0xda/0x100 drivers/tty/pty.c:118 n_tty_write+0xb38/0xfd0 drivers/tty/n_tty.c:2373 do_tty_write drivers/tty/tty_io.c:1018 [inline] file_tty_write.constprop.0+0x453/0x9c0 drivers/tty/tty_io.c:1089 call_write_iter include/linux/fs.h:1851 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x9ed/0xe10 fs/read_write.c:584 ksys_write+0x12b/0x250 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd other info that might help us debug this: Chain exists of: zonelist_update_seq.seqcount --> &port_lock_key --> &port->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&port->lock); lock(&port_lock_key); lock(&port->lock); lock(zonelist_update_seq.seqcount); *** DEADLOCK *** 5 locks held by syz-executor.0/5338: #0: ffff888074f13098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x26/0x80 drivers/tty/tty_ldisc.c:244 #1: ffff888074f13130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write_lock drivers/tty/tty_io.c:944 [inline] #1: ffff888074f13130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: do_tty_write drivers/tty/tty_io.c:967 [inline] #1: ffff888074f13130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: file_tty_write.constprop.0+0x251/0x9c0 drivers/tty/tty_io.c:1089 #2: ffff888074f132e8 (&tty->termios_rwsem){++++}-{3:3}, at: n_tty_write+0x1c3/0xfd0 drivers/tty/n_tty.c:2333 #3: ffffc9000332b380 (&ldata->output_lock){+.+.}-{3:3}, at: n_tty_write+0xb05/0xfd0 drivers/tty/n_tty.c:2372 #4: ffff88802445c158 (&port->lock){-...}-{2:2}, at: tty_insert_flip_string_and_push_buffer+0x2f/0x160 drivers/tty/tty_buffer.c:628 stack backtrace: CPU: 1 PID: 5338 Comm: syz-executor.0 Not tainted 6.3.0-rc7-syzkaller-00043-gaf67688dca57 #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3098 [inline] check_prevs_add kernel/locking/lockdep.c:3217 [inline] validate_chain kernel/locking/lockdep.c:3832 [inline] __lock_acquire+0x2ec7/0x5d40 kernel/locking/lockdep.c:5056 lock_acquire kernel/locking/lockdep.c:5669 [inline] lock_acquire+0x1af/0x520 kernel/locking/lockdep.c:5634 seqcount_lockdep_reader_access include/linux/seqlock.h:102 [inline] read_seqbegin include/linux/seqlock.h:836 [inline] zonelist_iter_begin mm/page_alloc.c:4765 [inline] __alloc_pages_slowpath.constprop.0+0x15a/0x2170 mm/page_alloc.c:5086 __alloc_pages+0x408/0x4a0 mm/page_alloc.c:5605 __alloc_pages_node include/linux/gfp.h:237 [inline] kmem_getpages mm/slab.c:1360 [inline] cache_grow_begin+0x9b/0x3b0 mm/slab.c:2570 cache_alloc_refill+0x27f/0x380 mm/slab.c:2943 ____cache_alloc mm/slab.c:3019 [inline] ____cache_alloc mm/slab.c:3002 [inline] __do_cache_alloc mm/slab.c:3202 [inline] slab_alloc_node mm/slab.c:3250 [inline] __kmem_cache_alloc_node+0x360/0x3f0 mm/slab.c:3541 __do_kmalloc_node mm/slab_common.c:966 [inline] __kmalloc+0x4e/0x190 mm/slab_common.c:980 kmalloc include/linux/slab.h:584 [inline] tty_buffer_alloc+0x275/0x2f0 drivers/tty/tty_buffer.c:180 __tty_buffer_request_room+0x15b/0x2d0 drivers/tty/tty_buffer.c:278 tty_insert_flip_string_fixed_flag+0x90/0x250 drivers/tty/tty_buffer.c:327 tty_insert_flip_string include/linux/tty_flip.h:41 [inline] tty_insert_flip_string_and_push_buffer+0x42/0x160 drivers/tty/tty_buffer.c:629 pty_write+0xda/0x100 drivers/tty/pty.c:118 n_tty_write+0xb38/0xfd0 drivers/tty/n_tty.c:2373 do_tty_write drivers/tty/tty_io.c:1018 [inline] file_tty_write.constprop.0+0x453/0x9c0 drivers/tty/tty_io.c:1089 call_write_iter include/linux/fs.h:1851 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x9ed/0xe10 fs/read_write.c:584 ksys_write+0x12b/0x250 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7ff02628c169 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ff026fb6168 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007ff0263ac050 RCX: 00007ff02628c169 RDX: 000000000000ff2e RSI: 00000000200021c0 RDI: 0000000000000006 RBP: 00007ff0262e7ca1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffd766ca28f R14: 00007ff026fb6300 R15: 0000000000022000