Hello,
syzbot found the following crash on:
HEAD commit: aec3002d Linux 4.19.56
git tree: linux-4.19.y
console output:
https://syzkaller.appspot.com/x/log.txt?x=1147a375a00000
kernel config:
https://syzkaller.appspot.com/x/.config?x=48b721ea0070d1cd
dashboard link:
https://syzkaller.appspot.com/bug?extid=84b2f2bda1c9e4d273ba
compiler: gcc (GCC) 9.0.0 20181231 (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+84b2f2...@syzkaller.appspotmail.com
futex_wake_op: syz-executor.1 tries to shift op by -1; fix this program
INFO: task syz-executor.3:14039 blocked for more than 140 seconds.
Not tainted 4.19.56 #28
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.3 D24056 14039 1 0x80000004
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x80d/0x1c70 kernel/sched/core.c:3474
schedule+0x92/0x1c0 kernel/sched/core.c:3518
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3576
__mutex_lock_common kernel/locking/mutex.c:1002 [inline]
__mutex_lock+0x726/0x1300 kernel/locking/mutex.c:1072
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
acct_get kernel/acct.c:161 [inline]
slow_acct_process kernel/acct.c:577 [inline]
acct_process+0x2e5/0x61e kernel/acct.c:605
do_exit+0x17be/0x2fa0 kernel/exit.c:866
do_group_exit+0x135/0x370 kernel/exit.c:979
get_signal+0x3ec/0x1fc0 kernel/signal.c:2574
do_signal+0x95/0x1960 arch/x86/kernel/signal.c:821
exit_to_usermode_loop+0x244/0x2c0 arch/x86/entry/common.c:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
do_syscall_64+0x53d/0x620 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4134aa
Code: 83 0d 01 00 00 88 44 1c 30 48 8d 43 01 48 83 f8 28 0f 83 f4 00 00 00
48 89 74 24 28 c6 44 1c 31 00 48 8d 44 24 30 48 89 44 24 <08> 48 8b 84 24
98 00 00 00 48 89 04 24 48 8b 44 24 68 48 89 44 24
RSP: 002b:00007ffff4d38ba8 EFLAGS: 00000246 ORIG_RAX: 000000000000003d
RAX: fffffffffffffe00 RBX: 00000000027eb940 RCX: 00000000004134aa
RDX: 0000000040000000 RSI: 00007ffff4d38be0 RDI: ffffffffffffffff
RBP: 00000000000035aa R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffff4d38be0 R14: 00000000027eb99b R15: 00007ffff4d38bf0
Showing all locks held in the system:
1 lock held by khungtaskd/1030:
#0: 0000000073f718b3 (rcu_read_lock){....}, at:
debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:4435
2 locks held by getty/7733:
#0: 00000000519690f0 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 00000000642f56b0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7734:
#0: 00000000ed592284 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 0000000019757d67 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7735:
#0: 00000000e6181a1a (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 000000004d802788 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7736:
#0: 00000000cc94a60b (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 000000002794f1b3 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7737:
#0: 00000000a688314b (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 0000000070e5a5a1 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7738:
#0: 000000006a51f4b4 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 00000000b6d9f010 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7739:
#0: 00000000073871ce (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 000000004f827171 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
1 lock held by syz-executor.3/14039:
#0: 00000000ed1c8588 (&acct->lock#2){+.+.}, at: acct_get kernel/acct.c:161
[inline]
#0: 00000000ed1c8588 (&acct->lock#2){+.+.}, at: slow_acct_process
kernel/acct.c:577 [inline]
#0: 00000000ed1c8588 (&acct->lock#2){+.+.}, at: acct_process+0x2e5/0x61e
kernel/acct.c:605
3 locks held by syz-executor.3/12890:
#0: 00000000ed1c8588 (&acct->lock#2){+.+.}, at: acct_get kernel/acct.c:161
[inline]
#0: 00000000ed1c8588 (&acct->lock#2){+.+.}, at: slow_acct_process
kernel/acct.c:577 [inline]
#0: 00000000ed1c8588 (&acct->lock#2){+.+.}, at: acct_process+0x2e5/0x61e
kernel/acct.c:605
#1: 00000000ec4a794e (sb_writers#4){.+.+}, at: file_start_write_trylock
include/linux/fs.h:2780 [inline]
#1: 00000000ec4a794e (sb_writers#4){.+.+}, at:
do_acct_process+0xf37/0x1150 kernel/acct.c:517
#2: 000000007681d426 (&sb->s_type->i_mutex_key#9){++++}, at: inode_trylock
include/linux/fs.h:767 [inline]
#2: 000000007681d426 (&sb->s_type->i_mutex_key#9){++++}, at:
ext4_file_write_iter+0x23f/0x1060 fs/ext4/file.c:232
=============================================
NMI backtrace for cpu 1
CPU: 1 PID: 1030 Comm: khungtaskd Not tainted 4.19.56 #28
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+0x172/0x1f0 lib/dump_stack.c:113
nmi_cpu_backtrace.cold+0x63/0xa4 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1b0/0x1f8 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:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline]
watchdog+0x9df/0xee0 kernel/hung_task.c:287
kthread+0x354/0x420 kernel/kthread.c:246
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
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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