syzbot

random: crng init done
INFO: task syzkaller684233:3852 blocked for more than 120 seconds.
      Not tainted 4.9.84-ga9d0273 #44
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syzkaller684233 D28224  3852   3850 0x00000000
 ffff8801d711c800 0000000000000000 ffff8801d8abb480 ffff8801d9b73000
 ffff8801db321b98 ffff8801d50a7a70 ffffffff838a438b ffff8801d711c800
 ffffffff8114529a 00fffc0000000000 ffff8801db322468 ffff8801db322490
Call Trace:
 [<ffffffff838a592f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3550
 [<ffffffff82ee4eac>] __lock_sock+0x13c/0x260 net/core/sock.c:2035
 [<ffffffff82ee50c6>] lock_sock_nested+0xf6/0x120 net/core/sock.c:2505
 [<ffffffff83528616>] lock_sock include/net/sock.h:1404 [inline]
 [<ffffffff83528616>] ipv6_getorigdst+0x136/0x610 net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c:238
 [<ffffffff830a301a>] nf_sockopt net/netfilter/nf_sockopt.c:103 [inline]
 [<ffffffff830a301a>] nf_getsockopt+0x6a/0xc0 net/netfilter/nf_sockopt.c:121
 [<ffffffff8347934e>] ipv6_getsockopt+0x1ce/0x250 net/ipv6/ipv6_sockglue.c:1347
 [<ffffffff8322f202>] tcp_getsockopt+0x82/0xd0 net/ipv4/tcp.c:3103
 [<ffffffff82edee85>] sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2665
 [<ffffffff82edc48a>] SYSC_getsockopt net/socket.c:1803 [inline]
 [<ffffffff82edc48a>] SyS_getsockopt+0x14a/0x230 net/socket.c:1785
 [<ffffffff81006504>] do_syscall_64+0x1a4/0x490 arch/x86/entry/common.c:282
 [<ffffffff838b53fd>] entry_SYSCALL_64_after_swapgs+0x47/0xc5

Showing all locks held in the system:
2 locks held by khungtaskd/514:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813730a5>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813730a5>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81238190>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
2 locks held by getty/3776:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838b3602>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff8200ab14>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
1 lock held by syzkaller684233/3852:
 #0:  (sk_lock-AF_INET6){+.+...}, at: [<ffffffff83479333>] lock_sock include/net/sock.h:1404 [inline]
 #0:  (sk_lock-AF_INET6){+.+...}, at: [<ffffffff83479333>] ipv6_getsockopt+0x1b3/0x250 net/ipv6/ipv6_sockglue.c:1346

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 514 Comm: khungtaskd Not tainted 4.9.84-ga9d0273 #44
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d86b7d00 ffffffff81d956b9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810bb190 ffff8801d86b7d38
 ffffffff81da07dd 0000000000000001 0000000000000000 ffff8801d711cc18
Call Trace:
 [<ffffffff81d956b9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d956b9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81da07dd>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81da0917>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810bb284>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81373670>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81373670>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81373670>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81373670>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff8119a7bd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838b558c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:361
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff838b4076