Date:   Fri, 08 Jun 2018 00:38:02 -0700
From:   syzbot <syzbot+831ee52a258e90882b4d@...kaller.appspotmail.com>
To:     linux-kernel@...r.kernel.org, pmladek@...e.com,
        rostedt@...dmis.org, sergey.senozhatsky@...il.com,
        syzkaller-bugs@...glegroups.com
Subject: possible deadlock in vprintk_emit

Hello,

syzbot found the following crash on:

HEAD commit:    1c8c5a9d38f6 Merge git://git.kernel.org/pub/scm/linux/kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=131d4ddf800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4f1acdf888c9d4e9
dashboard link: https://syzkaller.appspot.com/bug?extid=831ee52a258e90882b4d
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+831ee52a258e90882b4d@...kaller.appspotmail.com

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000016
R13: 00000000004be500 R14: 00000000004ccad8 R15: 0000000000000000
CPU: 0 PID: 19202 Comm: syz-executor2 Not tainted 4.17.0+ #89

======================================================
WARNING: possible circular locking dependency detected
4.17.0+ #89 Not tainted
------------------------------------------------------
syz-executor6/19187 is trying to acquire lock:
000000006e810651 (console_owner){-.-.}, at: console_trylock_spinning  
kernel/printk/printk.c:1651 [inline]
000000006e810651 (console_owner){-.-.}, at: vprintk_emit+0x826/0xde0  
kernel/printk/printk.c:1906

but task is already holding lock:
000000004ec3be2c (&(&port->lock)->rlock){-.-.}, at: pty_write+0xf9/0x1f0  
drivers/tty/pty.c:119

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&(&port->lock)->rlock){-.-.}:
        __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
        _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
        tty_port_tty_get+0x20/0x80 drivers/tty/tty_port.c:288
        tty_port_default_wakeup+0x15/0x40 drivers/tty/tty_port.c:47
        tty_port_tty_wakeup+0x5d/0x70 drivers/tty/tty_port.c:390
        uart_write_wakeup+0x44/0x60 drivers/tty/serial/serial_core.c:103
        serial8250_tx_chars+0x4be/0xb60  
drivers/tty/serial/8250/8250_port.c:1808
        serial8250_handle_irq.part.25+0x1ee/0x280  
drivers/tty/serial/8250/8250_port.c:1881
        serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1867  
[inline]
        serial8250_default_handle_irq+0xc8/0x150  
drivers/tty/serial/8250/8250_port.c:1897
        serial8250_interrupt+0xfa/0x1d0  
drivers/tty/serial/8250/8250_core.c:125
        __handle_irq_event_percpu+0x1c0/0xad0 kernel/irq/handle.c:149
        handle_irq_event_percpu+0x98/0x1c0 kernel/irq/handle.c:189
        handle_irq_event+0xa7/0x135 kernel/irq/handle.c:206
        handle_edge_irq+0x20f/0x870 kernel/irq/chip.c:791
        generic_handle_irq_desc include/linux/irqdesc.h:159 [inline]
        handle_irq+0x18c/0x2e7 arch/x86/kernel/irq_64.c:77
        do_IRQ+0x78/0x190 arch/x86/kernel/irq.c:245
        ret_from_intr+0x0/0x1e
        native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54
        arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline]
        default_idle+0xc2/0x440 arch/x86/kernel/process.c:500
        arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:491
        default_idle_call+0x6d/0x90 kernel/sched/idle.c:93
        cpuidle_idle_call kernel/sched/idle.c:153 [inline]
        do_idle+0x395/0x560 kernel/sched/idle.c:262
        cpu_startup_entry+0x104/0x120 kernel/sched/idle.c:368
        start_secondary+0x42b/0x5c0 arch/x86/kernel/smpboot.c:265
        secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:242

-> #1 (&port_lock_key){-.-.}:
        __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
        _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
        serial8250_console_write+0x8d5/0xb00  
drivers/tty/serial/8250/8250_port.c:3230
        univ8250_console_write+0x5f/0x70  
drivers/tty/serial/8250/8250_core.c:590
        call_console_drivers kernel/printk/printk.c:1718 [inline]
        console_unlock+0xa9d/0x10a0 kernel/printk/printk.c:2389
        vprintk_emit+0x6b2/0xde0 kernel/printk/printk.c:1907
        vprintk_default+0x28/0x30 kernel/printk/printk.c:1948
        vprintk_func+0x7a/0xe7 kernel/printk/printk_safe.c:382
        printk+0x9e/0xba kernel/printk/printk.c:1981
        register_console+0x7e7/0xc00 kernel/printk/printk.c:2704
        univ8250_console_init+0x3f/0x4b  
drivers/tty/serial/8250/8250_core.c:685
        console_init+0x6d9/0xa38 kernel/printk/printk.c:2788
        start_kernel+0x608/0x92d init/main.c:661
        x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:452
        x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:433
        secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:242

-> #0 (console_owner){-.-.}:
        lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3924
        console_trylock_spinning kernel/printk/printk.c:1672 [inline]
        vprintk_emit+0x884/0xde0 kernel/printk/printk.c:1906
        vprintk_default+0x28/0x30 kernel/printk/printk.c:1948
        vprintk_func+0x7a/0xe7 kernel/printk/printk_safe.c:382
        printk+0x9e/0xba kernel/printk/printk.c:1981
        fail_dump lib/fault-inject.c:44 [inline]
        should_fail+0x97a/0xbcd lib/fault-inject.c:149
        __should_failslab+0x124/0x180 mm/failslab.c:32
        should_failslab+0x9/0x14 mm/slab_common.c:1522
        slab_pre_alloc_hook mm/slab.h:423 [inline]
        slab_alloc mm/slab.c:3378 [inline]
        __do_kmalloc mm/slab.c:3716 [inline]
        __kmalloc+0x63/0x760 mm/slab.c:3727
        kmalloc include/linux/slab.h:518 [inline]
        tty_buffer_alloc drivers/tty/tty_buffer.c:170 [inline]
        __tty_buffer_request_room+0x2d2/0x7f0 drivers/tty/tty_buffer.c:268
        tty_insert_flip_string_fixed_flag+0x8d/0x1f0  
drivers/tty/tty_buffer.c:313
        tty_insert_flip_string include/linux/tty_flip.h:37 [inline]
        pty_write+0x12c/0x1f0 drivers/tty/pty.c:121
        tty_put_char+0x129/0x150 drivers/tty/tty_io.c:2865
        __process_echoes+0x4d9/0x8d0 drivers/tty/n_tty.c:703
        process_echoes+0xfc/0x170 drivers/tty/n_tty.c:781
        n_tty_set_termios+0xb56/0xe80 drivers/tty/n_tty.c:1837
        tty_set_termios+0x7a0/0xac0 drivers/tty/tty_ioctl.c:341
        set_termios+0x41e/0x7d0 drivers/tty/tty_ioctl.c:414
        tty_mode_ioctl+0x535/0xb50 drivers/tty/tty_ioctl.c:747
        n_tty_ioctl_helper+0x54/0x3b0 drivers/tty/tty_ioctl.c:940
        n_tty_ioctl+0x54/0x320 drivers/tty/n_tty.c:2441
        tty_ioctl+0x5e1/0x1870 drivers/tty/tty_io.c:2655
        vfs_ioctl fs/ioctl.c:46 [inline]
        file_ioctl fs/ioctl.c:500 [inline]
        do_vfs_ioctl+0x1cf/0x16f0 fs/ioctl.c:684
        ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
        __do_sys_ioctl fs/ioctl.c:708 [inline]
        __se_sys_ioctl fs/ioctl.c:706 [inline]
        __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706
        do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
        entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Chain exists of:
   console_owner --> &port_lock_key --> &(&port->lock)->rlock

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&(&port->lock)->rlock);
                                lock(&port_lock_key);
                                lock(&(&port->lock)->rlock);
   lock(console_owner);

  *** DEADLOCK ***

5 locks held by syz-executor6/19187:
  #0: 000000007080a3ba (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1: 000000006fe00659 (&o_tty->termios_rwsem/1){++++}, at:  
tty_set_termios+0xfd/0xac0 drivers/tty/tty_ioctl.c:328
  #2: 000000007080a3ba (&tty->ldisc_sem){++++}, at: tty_ldisc_ref+0x22/0x90  
drivers/tty/tty_ldisc.c:284
  #3: 00000000f8d1ab16 (&ldata->output_lock){+.+.}, at:  
process_echoes+0xb6/0x170 drivers/tty/n_tty.c:779
  #4: 000000004ec3be2c (&(&port->lock)->rlock){-.-.}, at:  
pty_write+0xf9/0x1f0 drivers/tty/pty.c:119

stack backtrace:
CPU: 1 PID: 19187 Comm: syz-executor6 Not tainted 4.17.0+ #89
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
  print_circular_bug.isra.36.cold.56+0x1bd/0x27d  
kernel/locking/lockdep.c:1227
  check_prev_add kernel/locking/lockdep.c:1867 [inline]
  check_prevs_add kernel/locking/lockdep.c:1980 [inline]
  validate_chain kernel/locking/lockdep.c:2421 [inline]
  __lock_acquire+0x343e/0x5140 kernel/locking/lockdep.c:3435
  lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3924
  console_trylock_spinning kernel/printk/printk.c:1672 [inline]
  vprintk_emit+0x884/0xde0 kernel/printk/printk.c:1906
  vprintk_default+0x28/0x30 kernel/printk/printk.c:1948
  vprintk_func+0x7a/0xe7 kernel/printk/printk_safe.c:382
  printk+0x9e/0xba kernel/printk/printk.c:1981
  fail_dump lib/fault-inject.c:44 [inline]
  should_fail+0x97a/0xbcd lib/fault-inject.c:149
  __should_failslab+0x124/0x180 mm/failslab.c:32
  should_failslab+0x9/0x14 mm/slab_common.c:1522
  slab_pre_alloc_hook mm/slab.h:423 [inline]
  slab_alloc mm/slab.c:3378 [inline]
  __do_kmalloc mm/slab.c:3716 [inline]
  __kmalloc+0x63/0x760 mm/slab.c:3727
  kmalloc include/linux/slab.h:518 [inline]
  tty_buffer_alloc drivers/tty/tty_buffer.c:170 [inline]
  __tty_buffer_request_room+0x2d2/0x7f0 drivers/tty/tty_buffer.c:268
  tty_insert_flip_string_fixed_flag+0x8d/0x1f0 drivers/tty/tty_buffer.c:313
  tty_insert_flip_string include/linux/tty_flip.h:37 [inline]
  pty_write+0x12c/0x1f0 drivers/tty/pty.c:121
  tty_put_char+0x129/0x150 drivers/tty/tty_io.c:2865
  __process_echoes+0x4d9/0x8d0 drivers/tty/n_tty.c:703
  process_echoes+0xfc/0x170 drivers/tty/n_tty.c:781
  n_tty_set_termios+0xb56/0xe80 drivers/tty/n_tty.c:1837
  tty_set_termios+0x7a0/0xac0 drivers/tty/tty_ioctl.c:341
  set_termios+0x41e/0x7d0 drivers/tty/tty_ioctl.c:414
  tty_mode_ioctl+0x535/0xb50 drivers/tty/tty_ioctl.c:747
  n_tty_ioctl_helper+0x54/0x3b0 drivers/tty/tty_ioctl.c:940
  n_tty_ioctl+0x54/0x320 drivers/tty/n_tty.c:2441
  tty_ioctl+0x5e1/0x1870 drivers/tty/tty_io.c:2655
  vfs_ioctl fs/ioctl.c:46 [inline]
  file_ioctl fs/ioctl.c:500 [inline]
  do_vfs_ioctl+0x1cf/0x16f0 fs/ioctl.c:684
  ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
  __do_sys_ioctl fs/ioctl.c:708 [inline]
  __se_sys_ioctl fs/ioctl.c:706 [inline]
  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4559f9
Code: 1d ba fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 .
Lost 23 message(s)!
IPVS: length: 236 != 24
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
IPVS: length: 236 != 24
  fail_dump lib/fault-inject.c:51 [inline]
  should_fail.cold.4+0xa/0x1a lib/fault-inject.c:149
  __should_failslab+0x124/0x180 mm/failslab.c:32
  should_failslab+0x9/0x14 mm/slab_common.c:1522
  slab_pre_alloc_hook mm/slab.h:423 [inline]
  slab_alloc_node mm/slab.c:3299 [inline]
  kmem_cache_alloc_node_trace+0x26f/0x770 mm/slab.c:3661
  __do_kmalloc_node mm/slab.c:3681 [inline]
  __kmalloc_node_track_caller+0x33/0x70 mm/slab.c:3696
  __kmalloc_reserve.isra.39+0x3a/0xe0 net/core/skbuff.c:137
  __alloc_skb+0x14d/0x780 net/core/skbuff.c:205
  alloc_skb include/linux/skbuff.h:987 [inline]
  netlink_alloc_large_skb net/netlink/af_netlink.c:1182 [inline]
  netlink_sendmsg+0xb01/0xfa0 net/netlink/af_netlink.c:1876
  sock_sendmsg_nosec net/socket.c:633 [inline]
  sock_sendmsg+0xd5/0x120 net/socket.c:643
  ___sys_sendmsg+0x805/0x940 net/socket.c:2149
  __sys_sendmsg+0x115/0x270 net/socket.c:2187
  __do_sys_sendmsg net/socket.c:2196 [inline]
  __se_sys_sendmsg net/socket.c:2194 [inline]
  __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2194
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4559f9
Code: 1d ba fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 eb b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fe47fbe2c68 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fe47fbe36d4 RCX: 00000000004559f9
RDX: 0000000000000000 RSI: 0000000020000900 RDI: 0000000000000014
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000015
R13: 00000000004c08de R14: 00000000004d00d8 R15: 0000000000000001
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
nla_parse: 5 callbacks suppressed
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.
netlink: 8 bytes leftover after parsing attributes in process  
`syz-executor2'.


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@...glegroups.com.

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