Re: [syzbot] INFO: task hung in fuse_simple_request

[Dmitry Vyukov]

",On Fri, 6 Aug 2021 at 10:54, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
>
> Hi,
>
> I'm not sure what to make of this report.
>
> Does syzbot try to kill all tasks before generating such a hung task report?
>
> Does it use the fuse specific /sys/fs/fuse/connections/*/abort to
> terminate stuck filesystems?

Hi Miklos,

Grepping the C reproducer for "/sys/fs/fuse/connections", it seems
that it tries to abort all connections.


> Thanks,
> Miklos
>
> On Sat, 17 Jul 2021 at 04:28, syzbot
> <syzbot+46fe899420456e014d6b@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > syzbot has found a reproducer for the following issue on:
> >
> > HEAD commit:    d936eb238744 Revert "Makefile: Enable -Wimplicit-fallthrou..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1492834a300000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=73e52880ded966e4
> > dashboard link: https://syzkaller.appspot.com/bug?extid=46fe899420456e014d6b
> > compiler:       Debian clang version 11.0.1-2
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=165fc902300000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1130705c300000
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+46fe899420456e014d6b@xxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > INFO: task syz-executor874:8578 blocked for more than 143 seconds.
> >       Not tainted 5.14.0-rc1-syzkaller #0
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > task:syz-executor874 state:D stack:26768 pid: 8578 ppid:  8450 flags:0x00004004
> > Call Trace:
> >  context_switch kernel/sched/core.c:4683 [inline]
> >  __schedule+0xc07/0x11f0 kernel/sched/core.c:5940
> >  schedule+0x14b/0x210 kernel/sched/core.c:6019
> >  request_wait_answer fs/fuse/dev.c:411 [inline]
> >  __fuse_request_send fs/fuse/dev.c:430 [inline]
> >  fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
> >  fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
> >  vfs_getattr fs/stat.c:142 [inline]
> >  vfs_statx+0x1ba/0x3d0 fs/stat.c:207
> >  vfs_fstatat fs/stat.c:225 [inline]
> >  __do_sys_newfstatat fs/stat.c:394 [inline]
> >  __se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > RIP: 0033:0x446039
> > RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
> > RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
> > RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
> > RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
> > R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
> > INFO: task syz-executor874:8582 blocked for more than 143 seconds.
> >       Not tainted 5.14.0-rc1-syzkaller #0
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > task:syz-executor874 state:D stack:25368 pid: 8582 ppid:  8451 flags:0x00004004
> > Call Trace:
> >  context_switch kernel/sched/core.c:4683 [inline]
> >  __schedule+0xc07/0x11f0 kernel/sched/core.c:5940
> >  schedule+0x14b/0x210 kernel/sched/core.c:6019
> >  request_wait_answer fs/fuse/dev.c:411 [inline]
> >  __fuse_request_send fs/fuse/dev.c:430 [inline]
> >  fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
> >  fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
> >  vfs_getattr fs/stat.c:142 [inline]
> >  vfs_statx+0x1ba/0x3d0 fs/stat.c:207
> >  vfs_fstatat fs/stat.c:225 [inline]
> >  __do_sys_newfstatat fs/stat.c:394 [inline]
> >  __se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > RIP: 0033:0x446039
> > RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
> > RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
> > RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
> > RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
> > R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
> > INFO: task syz-executor874:8597 blocked for more than 143 seconds.
> >       Not tainted 5.14.0-rc1-syzkaller #0
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > task:syz-executor874 state:D stack:24784 pid: 8597 ppid:  8448 flags:0x00004004
> > Call Trace:
> >  context_switch kernel/sched/core.c:4683 [inline]
> >  __schedule+0xc07/0x11f0 kernel/sched/core.c:5940
> >  schedule+0x14b/0x210 kernel/sched/core.c:6019
> >  request_wait_answer fs/fuse/dev.c:411 [inline]
> >  __fuse_request_send fs/fuse/dev.c:430 [inline]
> >  fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
> >  fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
> >  vfs_getattr fs/stat.c:142 [inline]
> >  vfs_statx+0x1ba/0x3d0 fs/stat.c:207
> >  vfs_fstatat fs/stat.c:225 [inline]
> >  __do_sys_newfstatat fs/stat.c:394 [inline]
> >  __se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > RIP: 0033:0x446039
> > RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
> > RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
> > RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
> > RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
> > R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
> > INFO: task syz-executor874:8601 blocked for more than 144 seconds.
> >       Not tainted 5.14.0-rc1-syzkaller #0
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > task:syz-executor874 state:D stack:24784 pid: 8601 ppid:  8452 flags:0x00004004
> > Call Trace:
> >  context_switch kernel/sched/core.c:4683 [inline]
> >  __schedule+0xc07/0x11f0 kernel/sched/core.c:5940
> >  schedule+0x14b/0x210 kernel/sched/core.c:6019
> >  request_wait_answer fs/fuse/dev.c:411 [inline]
> >  __fuse_request_send fs/fuse/dev.c:430 [inline]
> >  fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
> >  fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
> >  vfs_getattr fs/stat.c:142 [inline]
> >  vfs_statx+0x1ba/0x3d0 fs/stat.c:207
> >  vfs_fstatat fs/stat.c:225 [inline]
> >  __do_sys_newfstatat fs/stat.c:394 [inline]
> >  __se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > RIP: 0033:0x446039
> > RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
> > RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
> > RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
> > RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
> > R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
> > INFO: task syz-executor874:8617 blocked for more than 144 seconds.
> >       Not tainted 5.14.0-rc1-syzkaller #0
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > task:syz-executor874 state:D stack:26768 pid: 8617 ppid:  8451 flags:0x00004004
> > Call Trace:
> >  context_switch kernel/sched/core.c:4683 [inline]
> >  __schedule+0xc07/0x11f0 kernel/sched/core.c:5940
> >  schedule+0x14b/0x210 kernel/sched/core.c:6019
> >  request_wait_answer fs/fuse/dev.c:411 [inline]
> >  __fuse_request_send fs/fuse/dev.c:430 [inline]
> >  fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
> >  fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
> >  vfs_getattr fs/stat.c:142 [inline]
> >  vfs_statx+0x1ba/0x3d0 fs/stat.c:207
> >  vfs_fstatat fs/stat.c:225 [inline]
> >  __do_sys_newfstatat fs/stat.c:394 [inline]
> >  __se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > RIP: 0033:0x446039
> > RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
> > RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
> > RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
> > RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
> > R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
> > INFO: task syz-executor874:8626 blocked for more than 144 seconds.
> >       Not tainted 5.14.0-rc1-syzkaller #0
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > task:syz-executor874 state:D stack:24784 pid: 8626 ppid:  8450 flags:0x00004004
> > Call Trace:
> >  context_switch kernel/sched/core.c:4683 [inline]
> >  __schedule+0xc07/0x11f0 kernel/sched/core.c:5940
> >  schedule+0x14b/0x210 kernel/sched/core.c:6019
> >  request_wait_answer fs/fuse/dev.c:411 [inline]
> >  __fuse_request_send fs/fuse/dev.c:430 [inline]
> >  fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
> >  fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
> >  vfs_getattr fs/stat.c:142 [inline]
> >  vfs_statx+0x1ba/0x3d0 fs/stat.c:207
> >  vfs_fstatat fs/stat.c:225 [inline]
> >  __do_sys_newfstatat fs/stat.c:394 [inline]
> >  __se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > RIP: 0033:0x446039
> > RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
> > RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
> > RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
> > RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
> > R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
> > INFO: task syz-executor874:8630 blocked for more than 145 seconds.
> >       Not tainted 5.14.0-rc1-syzkaller #0
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > task:syz-executor874 state:D stack:24784 pid: 8630 ppid:  8452 flags:0x00004004
> > Call Trace:
> >  context_switch kernel/sched/core.c:4683 [inline]
> >  __schedule+0xc07/0x11f0 kernel/sched/core.c:5940
> >  schedule+0x14b/0x210 kernel/sched/core.c:6019
> >  request_wait_answer fs/fuse/dev.c:411 [inline]
> >  __fuse_request_send fs/fuse/dev.c:430 [inline]
> >  fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
> >  fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
> >  vfs_getattr fs/stat.c:142 [inline]
> >  vfs_statx+0x1ba/0x3d0 fs/stat.c:207
> >  vfs_fstatat fs/stat.c:225 [inline]
> >  __do_sys_newfstatat fs/stat.c:394 [inline]
> >  __se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > RIP: 0033:0x446039
> > RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
> > RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
> > RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
> > RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
> > R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
> > INFO: task syz-executor874:8634 blocked for more than 145 seconds.
> >       Not tainted 5.14.0-rc1-syzkaller #0
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > task:syz-executor874 state:D stack:26640 pid: 8634 ppid:  8448 flags:0x00004004
> > Call Trace:
> >  context_switch kernel/sched/core.c:4683 [inline]
> >  __schedule+0xc07/0x11f0 kernel/sched/core.c:5940
> >  schedule+0x14b/0x210 kernel/sched/core.c:6019
> >  request_wait_answer fs/fuse/dev.c:411 [inline]
> >  __fuse_request_send fs/fuse/dev.c:430 [inline]
> >  fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
> >  fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
> >  vfs_getattr fs/stat.c:142 [inline]
> >  vfs_statx+0x1ba/0x3d0 fs/stat.c:207
> >  vfs_fstatat fs/stat.c:225 [inline]
> >  __do_sys_newfstatat fs/stat.c:394 [inline]
> >  __se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > RIP: 0033:0x446039
> > RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
> > RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
> > RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
> > RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
> > R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
> > INFO: task syz-executor874:8657 blocked for more than 145 seconds.
> >       Not tainted 5.14.0-rc1-syzkaller #0
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > task:syz-executor874 state:D stack:26768 pid: 8657 ppid:  8450 flags:0x00004004
> > Call Trace:
> >  context_switch kernel/sched/core.c:4683 [inline]
> >  __schedule+0xc07/0x11f0 kernel/sched/core.c:5940
> >  schedule+0x14b/0x210 kernel/sched/core.c:6019
> >  request_wait_answer fs/fuse/dev.c:411 [inline]
> >  __fuse_request_send fs/fuse/dev.c:430 [inline]
> >  fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
> >  fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
> >  vfs_getattr fs/stat.c:142 [inline]
> >  vfs_statx+0x1ba/0x3d0 fs/stat.c:207
> >  vfs_fstatat fs/stat.c:225 [inline]
> >  __do_sys_newfstatat fs/stat.c:394 [inline]
> >  __se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > RIP: 0033:0x446039
> > RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
> > RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
> > RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
> > RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
> > R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
> > INFO: task syz-executor874:8665 blocked for more than 145 seconds.
> >       Not tainted 5.14.0-rc1-syzkaller #0
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > task:syz-executor874 state:D stack:26768 pid: 8665 ppid:  8452 flags:0x00004004
> > Call Trace:
> >  context_switch kernel/sched/core.c:4683 [inline]
> >  __schedule+0xc07/0x11f0 kernel/sched/core.c:5940
> >  schedule+0x14b/0x210 kernel/sched/core.c:6019
> >  request_wait_answer fs/fuse/dev.c:411 [inline]
> >  __fuse_request_send fs/fuse/dev.c:430 [inline]
> >  fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
> >  fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
> >  vfs_getattr fs/stat.c:142 [inline]
> >  vfs_statx+0x1ba/0x3d0 fs/stat.c:207
> >  vfs_fstatat fs/stat.c:225 [inline]
> >  __do_sys_newfstatat fs/stat.c:394 [inline]
> >  __se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > RIP: 0033:0x446039
> > RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
> > RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
> > RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
> > RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
> > R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
> >
> > Showing all locks held in the system:
> > 1 lock held by ksoftirqd/0/13:
> >  #0: ffff8880b9c514d8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x1b/0x30 kernel/sched/core.c:460
> > 1 lock held by khungtaskd/1644:
> >  #0: ffffffff8c7177c0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30 arch/x86/pci/mmconfig_64.c:151
> > 1 lock held by in:imklog/8138:
> >  #0: ffff888019edb270 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x24e/0x2f0 fs/file.c:974
> > no locks held by syz-executor874/16040.
> >
> > =============================================
> >
> > NMI backtrace for cpu 1
> > CPU: 1 PID: 1644 Comm: khungtaskd Not tainted 5.14.0-rc1-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > Call Trace:
> >  __dump_stack lib/dump_stack.c:88 [inline]
> >  dump_stack_lvl+0x1d3/0x29f lib/dump_stack.c:105
> >  nmi_cpu_backtrace+0x16c/0x190 lib/nmi_backtrace.c:105
> >  nmi_trigger_cpumask_backtrace+0x191/0x2f0 lib/nmi_backtrace.c:62
> >  trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
> >  check_hung_uninterruptible_tasks kernel/hung_task.c:210 [inline]
> >  watchdog+0xd06/0xd50 kernel/hung_task.c:295
> >  kthread+0x453/0x480 kernel/kthread.c:319
> >  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> > Sending NMI from CPU 1 to CPUs 0:
> > NMI backtrace for cpu 0
> > CPU: 0 PID: 8453 Comm: syz-executor874 Not tainted 5.14.0-rc1-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > RIP: 0010:put_pid+0x0/0x130 kernel/pid.c:106
> > Code: 1f 84 00 00 00 00 00 0f 1f 00 be af 00 00 00 48 c7 c7 40 99 5c 8c e8 ff d4 74 00 c3 cc cc cc cc cc cc cc cc cc cc cc cc cc cc <55> 41 57 41 56 41 54 53 49 89 ff e8 c0 a3 2b 00 4d 85 ff 0f 84 aa
> > RSP: 0018:ffffc9000198fc78 EFLAGS: 00000286
> > RAX: 0000000000000000 RBX: dffffc0000000000 RCX: 0000000000000001
> > RDX: dffffc0000000000 RSI: 0000000000000001 RDI: 0000000000000000
> > RBP: ffffc9000198fd90 R08: ffffffff81869020 R09: ffffed1002bf8685
> > R10: ffffed1002bf8685 R11: 0000000000000000 R12: 0000000000000000
> > R13: 1ffff92000331f94 R14: 1ffff92000331f9b R15: 0000000000000000
> > FS:  00000000020ba300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007fbb52603718 CR3: 00000000366ee000 CR4: 00000000001506f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >  kernel_wait4+0x27f/0x380 kernel/exit.c:1678
> >  __do_sys_wait4 kernel/exit.c:1705 [inline]
> >  __se_sys_wait4 kernel/exit.c:1701 [inline]
> >  __x64_sys_wait4+0x117/0x1c0 kernel/exit.c:1701
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > RIP: 0033:0x444826
> > Code: 0f 1f 40 00 31 c9 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 49 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 11 b8 3d 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 5a c3 90 48 83 ec 28 89 54 24 14 48 89 74 24
> > RSP: 002b:00007fff50fbe958 EFLAGS: 00000246 ORIG_RAX: 000000000000003d
> > RAX: ffffffffffffffda RBX: 00007fff50fbea10 RCX: 0000000000444826
> > RDX: 0000000040000001 RSI: 00007fff50fbe98c RDI: 00000000ffffffff
> > RBP: 00007fff50fbe98c R08: 00007fff50fec080 R09: 0000000000000010
> > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000000f4240
> > R13: 0000000000001eee R14: 00007fff50fbe9e0 R15: 00007fff50fbe9d0
> >
>
> --
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