linux-kernel - Re: BUG: unable to handle kernel paging request in __switch

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Date:   Fri, 15 Dec 2017 10:51:56 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        syzbot 
        <bot+1f445b1009b8eeededa30fe62ccf685f2ec9d155@...kaller.appspotmail.com>,
        Borislav Petkov <bp@...e.de>,
        Dmitry Safonov <dsafonov@...tuozzo.com>,
        Peter Anvin <hpa@...or.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Kyle Huey <me@...ehuey.com>, Ingo Molnar <mingo@...hat.com>,
        syzkaller-bugs@...glegroups.com,
        the arch/x86 maintainers <x86@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        KVM list <kvm@...r.kernel.org>, tianyu.lan@...el.com,
        James Mattson <jmattson@...gle.com>,
        Wanpeng Li <kernellwp@...il.com>
Subject: Re: BUG: unable to handle kernel paging request in __switch_to


> int main()
> {
>   int fd = open("/dev/kvm", 0x80102ul);
>   int vm = ioctl(fd, KVM_CREATE_VM, 0);
>   int  cpu = ioctl(vm, KVM_CREATE_VCPU, 4);

Not even a memory region :) So maybe the first memory access directly
triggers a fault?

>   ioctl(cpu, KVM_RUN, 0);
>   return 0;
> }
> 
> And, yes, this in fact triggers instant reboot of kernel (running in qemu).
> Am I missing something here?
> 
> +kvm maintainers, you can see full thread here:
> https://groups.google.com/forum/#!topic/syzkaller-bugs/_oveOKGm3jw
> 


-- 

Thanks,

David / dhildenb