linux-kernel - Re: [syzbot] BUG: unable to handle kernel paging request in vmx_handle_exit

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Date:   Thu, 3 Nov 2022 18:42:24 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     syzbot <syzbot+8cdd16fd5a6c0565e227@...kaller.appspotmail.com>
Cc:     bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, pbonzini@...hat.com,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de, x86@...nel.org
Subject: Re: [syzbot] BUG: unable to handle kernel paging request in
 vmx_handle_exit_irqoff

On Wed, Nov 02, 2022, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    61c3426aca2c Add linux-next specific files for 20221102
> git tree:       linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=13596541880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=acb529cc910d907c
> dashboard link: https://syzkaller.appspot.com/bug?extid=8cdd16fd5a6c0565e227
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17d036de880000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11d5e00a880000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/cc56d88dd6a3/disk-61c3426a.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/5921b65b080f/vmlinux-61c3426a.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/39cbd355fedd/bzImage-61c3426a.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+8cdd16fd5a6c0565e227@...kaller.appspotmail.com
> 
> BUG: unable to handle page fault for address: fffffbc0000001d8
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 23ffe4067 P4D 23ffe4067 PUD 0 
> Oops: 0000 [#1] PREEMPT SMP KASAN
> CPU: 0 PID: 5404 Comm: syz-executor526 Not tainted 6.1.0-rc3-next-20221102-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022
> RIP: 0010:gate_offset arch/x86/include/asm/desc_defs.h:100 [inline]

Looks like a KASAN bug, the KVM side of things looks ok and that code hasn't been
touched in quite some time.  The actual explosion is in kasan_check_range(), not
KVM code.

I'll bisect, this repros very quickly for me.