kernel panic: Proc-less Page Fault in the Kernel at ADDR!

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 5e0dca91 iommu: use parse_cmd() for attach/detach
git tree: akaros
console output: https://syzkaller.appspot.com/x/log.txt?x=12506f02100000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b018fab5edd31b3
dashboard link: https://syzkaller.appspot.com/bug?extid=48a7fddce7d07eb5a4f2

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+48a7fd...@syzkaller.appspotmail.com

kernel panic at kern/arch/x86/trap.c:292, from core 0: Proc-less Page Fault in the Kernel at 0x0000000000000008!
HW TRAP frame at 0xfffffff001066ce0 on core 0
rax 0x0000000000000000
rbx 0x0000000000000000
rcx 0x0000000000000000
rdx 0xffff800034e855a0
rbp 0xfffffff001066de8
rsi 0xffff80007f5dbf90
rdi 0xffff80000d94b618
r8 0x0000000000020000
r9 0x0000000000000000
r10 0x0000000000000078
r11 0xffffffffc8f70bb8
r12 0xffffffffc200c220
r13 0x0000000000000000
r14 0x0000000000000002
r15 0x0000000000000000
trap 0x0000000e Page Fault
gsbs 0xffffffffc8f70b00
fsbs 0x0000000000000000
err 0x--------00000002
rip 0xffffffffc205bba3
cs 0x------------0008
flag 0x0000000000010202
rsp 0xfffffff001066da8
ss 0x------------0010
Backtrace of kernel context on Core 0:
#01 [<0xffffffffc205bba3>] in send_kernel_message at src/trap.c:133
#02 [<0xffffffffc200c28e>] in kthread_runnable at src/kthread.c:239
#03 [<0xffffffffc200c315>] in sem_up at src/kthread.c:550
#04 [<0xffffffffc20509fd>] in __sync_cb at src/rcu.c:111
#05 [<0xffffffffc2050a12>] in rcu_exec_cb at src/rcu.c:160
#06 [< [inline] >] in run_rcu_cbs at src/rcu.c:527
#06 [<0xffffffffc2050ce2>] in rcu_mgmt_ktask at src/rcu.c:553
#07 [<0xffffffffc200b994>] in __ktask_wrapper at src/kthread.c:292
#08 [<0xffffffffc205bfed>] in process_routine_kmsg at src/trap.c:241
#09 [<0xffffffffc205597e>] in __smp_idle at src/smp.c:78


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.