INFO: task hung in exit_aio

[syzbot]

Hello,

syzkaller hit the following crash on
82bcf1def3b5f1251177ad47c44f7e17af039b4b
git://git.cmpxchg.org/linux-mmots.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


INFO: task syzkaller265413:3189 blocked for more than 120 seconds.
Not tainted 4.15.0-rc2-mm1+ #39
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syzkaller265413 D24320 3189 3150 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2800 [inline]
__schedule+0x8eb/0x2060 kernel/sched/core.c:3376
schedule+0xf5/0x430 kernel/sched/core.c:3435
schedule_timeout+0x43a/0x560 kernel/time/timer.c:1776
do_wait_for_common kernel/sched/completion.c:91 [inline]
__wait_for_common kernel/sched/completion.c:112 [inline]
wait_for_common kernel/sched/completion.c:123 [inline]
wait_for_completion+0x44b/0x7b0 kernel/sched/completion.c:144
exit_aio+0x47f/0x530 fs/aio.c:903
__mmput kernel/fork.c:968 [inline]
mmput+0x1b1/0x6c0 kernel/fork.c:992
exit_mm kernel/exit.c:544 [inline]
do_exit+0x90a/0x1ae0 kernel/exit.c:856
do_group_exit+0x149/0x400 kernel/exit.c:972
SYSC_exit_group kernel/exit.c:983 [inline]
SyS_exit_group+0x1d/0x20 kernel/exit.c:981
entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x440a99
RSP: 002b:00007ffc5abebf68 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 0000000000440a99
RDX: 0000000000440a99 RSI: 0000000000000058 RDI: 0000000000000000
RBP: 000000000001cbc8 R08: 000000005abec108 R09: 0000000000401fd0
R10: 000000005abec108 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000401fd0 R14: 0000000000000000 R15: 0000000000000000

Showing all locks held in the system:
2 locks held by khungtaskd/673:
#0: (rcu_read_lock){....}, at: [<00000000a9ed5249>]
check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
#0: (rcu_read_lock){....}, at: [<00000000a9ed5249>] watchdog+0x1c5/0xd60
kernel/hung_task.c:249
#1: (tasklist_lock){.+.+}, at: [<0000000036eecee2>]
debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554
2 locks held by getty/3117:
#0: (&tty->ldisc_sem){++++}, at: [<000000008d3f9495>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fafb010f>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3118:
#0: (&tty->ldisc_sem){++++}, at: [<000000008d3f9495>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fafb010f>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3119:
#0: (&tty->ldisc_sem){++++}, at: [<000000008d3f9495>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fafb010f>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3120:
#0: (&tty->ldisc_sem){++++}, at: [<000000008d3f9495>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fafb010f>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3121:
#0: (&tty->ldisc_sem){++++}, at: [<000000008d3f9495>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fafb010f>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3122:
#0: (&tty->ldisc_sem){++++}, at: [<000000008d3f9495>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fafb010f>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3123:
#0: (&tty->ldisc_sem){++++}, at: [<000000008d3f9495>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fafb010f>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131

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

NMI backtrace for cpu 1
CPU: 1 PID: 673 Comm: khungtaskd Not tainted 4.15.0-rc2-mm1+ #39
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
nmi_trigger_cpumask_backtrace+0x122/0x180 lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline]
check_hung_task kernel/hung_task.c:132 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
watchdog+0x90c/0xd60 kernel/hung_task.c:249
kthread+0x37a/0x440 kernel/kthread.c:238
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10
arch/x86/include/asm/irqflags.h:54


---
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[Eric Biggers]

[+Cc linux-crypto]

Still happening occasionally, but the reproducer is using AF_ALG with the
"rfc4309(pcrypt(pcrypt(rfc4106(gcm(aes)))))" algorithm which means it's very
likely a duplicate of the recursive pcrypt bug, main thread here:
https://groups.google.com/d/msg/syzkaller-bugs/1_CXUd3gBcg/BvsRLH0lAgAJ

#syz dup: INFO: task hung in aead_recvmsg

- Eric