linux-kernel - Re: [syzbot] general protection fault in gfn_to

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Date:   Tue, 8 Jun 2021 16:48:15 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     syzbot <syzbot+fb0b6a7e8713aeb0319c@...kaller.appspotmail.com>
Cc:     bp@...en8.de, hpa@...or.com, jmattson@...gle.com, joro@...tes.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, pbonzini@...hat.com, rkrcmar@...hat.com,
        sean.j.christopherson@...el.com, syzkaller-bugs@...glegroups.com,
        tglx@...utronix.de, vkuznets@...hat.com, wanpengli@...cent.com,
        x86@...nel.org
Subject: Re: [syzbot] general protection fault in gfn_to_rmap (2)

On Tue, Jun 08, 2021, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    614124be Linux 5.13-rc5
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14a62298300000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=547a5e42ca601229
> dashboard link: https://syzkaller.appspot.com/bug?extid=fb0b6a7e8713aeb0319c
> compiler:       Debian clang version 11.0.1-2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11395057d00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12d2b797d00000
> 
> The issue was bisected to:
> 
> commit 9ec19493fb86d6d5fbf9286b94ff21e56ef66376
> Author: Sean Christopherson <sean.j.christopherson@...el.com>
> Date:   Tue Apr 2 15:03:11 2019 +0000
> 
>     KVM: x86: clear SMM flags before loading state while leaving SMM
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1437f9bbd00000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=1637f9bbd00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=1237f9bbd00000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+fb0b6a7e8713aeb0319c@...kaller.appspotmail.com
> Fixes: 9ec19493fb86 ("KVM: x86: clear SMM flags before loading state while leaving SMM")
> 
> L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details.
> general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> CPU: 1 PID: 8410 Comm: syz-executor382 Not tainted 5.13.0-rc5-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:__gfn_to_rmap arch/x86/kvm/mmu/mmu.c:935 [inline]

Oh joy.  SMM, rmaps, and memslots.  I'll take this one...