INFO: task hung in acct_process

From: syzbot
Date: Wed Oct 23 2019 - 03:20:11 EST

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Hello,

syzbot found the following crash on:

HEAD commit: 4f5cafb5 Linux 5.4-rc3
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14e1d2a0e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=de66e73d1c10cebb
dashboard link: https://syzkaller.appspot.com/bug?extid=bece7c62047c98a5aa90
compiler: clang version 9.0.0 (/home/glider/llvm/clang 80fee25776c2fb61e74c1ecb1a523375c2500b69)

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+bece7c62047c98a5aa90@xxxxxxxxxxxxxxxxxxxxxxxxx

INFO: task syz-executor.5:19837 blocked for more than 143 seconds.
Not tainted 5.4.0-rc3 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D24680 19837 1 0x80004004
Call Trace:
context_switch kernel/sched/core.c:3384 [inline]
__schedule+0x74b/0xb80 kernel/sched/core.c:4069
schedule+0x131/0x1e0 kernel/sched/core.c:4136
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:4195
__mutex_lock_common+0x1411/0x2e20 kernel/locking/mutex.c:1033
__mutex_lock kernel/locking/mutex.c:1103 [inline]
mutex_lock_nested+0x1b/0x30 kernel/locking/mutex.c:1118
acct_get kernel/acct.c:161 [inline]
slow_acct_process kernel/acct.c:577 [inline]
acct_process+0x3af/0x570 kernel/acct.c:605
do_exit+0x573/0x2190 kernel/exit.c:807
do_group_exit+0x15c/0x2b0 kernel/exit.c:921
get_signal+0x4ac/0x1d60 kernel/signal.c:2734
do_signal+0x37/0x640 arch/x86/kernel/signal.c:815
exit_to_usermode_loop arch/x86/entry/common.c:159 [inline]
prepare_exit_to_usermode+0x303/0x580 arch/x86/entry/common.c:194
syscall_return_slowpath+0x113/0x4a0 arch/x86/entry/common.c:274
do_syscall_64+0x11f/0x1c0 arch/x86/entry/common.c:300
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4139ea
Code: 00 48 89 04 24 48 c7 44 24 08 21 00 00 00 e8 ed 7e 01 00 0f 0b 48 89 1c 24 e8 b2 f9 03 00 48 8b 44 24 10 48 89 44 24 38 48 8b <4c> 24 08 48 89 4c 24 40 e8 69 88 01 00 48 8d 05 f3 a4 4e 00 48 89
RSP: 002b:00007ffcbd566058 EFLAGS: 00000246 ORIG_RAX: 000000000000003d
RAX: fffffffffffffe00 RBX: 0000000000bfa940 RCX: 00000000004139ea
RDX: 0000000040000000 RSI: 00007ffcbd566090 RDI: ffffffffffffffff
RBP: 00000000000039b0 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000011
R13: 00007ffcbd566090 R14: 0000000000bfa99b R15: 00007ffcbd5660a0

Showing all locks held in the system:
1 lock held by khungtaskd/1064:
#0: ffffffff888d3f80 (rcu_read_lock){....}, at: rcu_lock_acquire+0x4/0x30 include/linux/rcupdate.h:207
1 lock held by rsyslogd/7848:
#0: ffff8880a2fecde0 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x243/0x2e0 fs/file.c:801
2 locks held by getty/7938:
#0: ffff88809a98c090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
#1: ffffc90005f012e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 drivers/tty/n_tty.c:2156
2 locks held by getty/7939:
#0: ffff8880a58d5090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
#1: ffffc90005f152e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 drivers/tty/n_tty.c:2156
2 locks held by getty/7940:
#0: ffff8880a12f7090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
#1: ffffc90005f092e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 drivers/tty/n_tty.c:2156
2 locks held by getty/7941:
#0: ffff8880a7a88090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
#1: ffffc90005f1d2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 drivers/tty/n_tty.c:2156
2 locks held by getty/7942:
#0: ffff8880a892b090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
#1: ffffc90005f292e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 drivers/tty/n_tty.c:2156
2 locks held by getty/7943:
#0: ffff8880a7bb4090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
#1: ffffc90005f252e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 drivers/tty/n_tty.c:2156
2 locks held by getty/7944:
#0: ffff8880993fd090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
#1: ffffc90005ef12e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 drivers/tty/n_tty.c:2156
1 lock held by syz-executor.5/19837:
#0: ffff8880a7dbb0f0 (&acct->lock#2){+.+.}, at: acct_get kernel/acct.c:161 [inline]
#0: ffff8880a7dbb0f0 (&acct->lock#2){+.+.}, at: slow_acct_process kernel/acct.c:577 [inline]
#0: ffff8880a7dbb0f0 (&acct->lock#2){+.+.}, at: acct_process+0x3af/0x570 kernel/acct.c:605
3 locks held by syz-executor.5/17136:
#0: ffff8880a7dbb0f0 (&acct->lock#2){+.+.}, at: acct_get kernel/acct.c:161 [inline]
#0: ffff8880a7dbb0f0 (&acct->lock#2){+.+.}, at: slow_acct_process kernel/acct.c:577 [inline]
#0: ffff8880a7dbb0f0 (&acct->lock#2){+.+.}, at: acct_process+0x3af/0x570 kernel/acct.c:605
#1: ffff88809b314420 (sb_writers#3){.+.+}, at: file_start_write_trylock include/linux/fs.h:2889 [inline]
#1: ffff88809b314420 (sb_writers#3){.+.+}, at: do_acct_process+0xf0c/0x1370 kernel/acct.c:517
#2: ffff888093bd4a48 (&sb->s_type->i_mutex_key#10){++++}, at: inode_trylock include/linux/fs.h:811 [inline]
#2: ffff888093bd4a48 (&sb->s_type->i_mutex_key#10){++++}, at: ext4_file_write_iter+0x1a8/0x15b0 fs/ext4/file.c:234

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

NMI backtrace for cpu 1
CPU: 1 PID: 1064 Comm: khungtaskd Not tainted 5.4.0-rc3 #0
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+0x1d8/0x2f8 lib/dump_stack.c:113
nmi_cpu_backtrace+0xaf/0x1a0 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x174/0x290 lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x10/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace+0x17/0x20 include/linux/nmi.h:146
check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline]
watchdog+0xbb9/0xbd0 kernel/hung_task.c:289
kthread+0x332/0x350 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60

---
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Next message: Markus Elfring: "Re: [PATCH] clocksource/drivers: Fix error handling in ttc_setup_clocksource"
Previous message: Piotr Sarna: "Re: [PATCH] hugetlbfs: add O_TMPFILE support"
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