Date:   Tue, 11 Jan 2022 19:37:50 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     "Sabri N. Ferreiro" <snferreiro1@gmail.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, sunhao.th@gmail.com
Subject: Re: WARNING in kvm_mmu_uninit_tdp_mmu
Message-ID: <Yd3cjllVD4vS17kG@google.com>
References: <CAKG+3NTTHD3iXgK67B4R3e+ScZ+vW5H4FdwLYy9CR5oBF44DOA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAKG+3NTTHD3iXgK67B4R3e+ScZ+vW5H4FdwLYy9CR5oBF44DOA@mail.gmail.com>
Precedence: bulk

On Sun, Jan 09, 2022, Sabri N. Ferreiro wrote:
> Hi,
> 
> When using Syzkaller to fuzz the Linux kernel, it triggers the following crash.
> 
> HEAD commit: a7904a538933 Linux 5.16-rc6
> git tree: upstream
> console output: https://pastebin.com/raw/keWCUeJ2
> kernel config: https://docs.google.com/document/d/1w94kqQ4ZSIE6BW-5WIhqp4_Zh7XTPH57L5OF2Xb6O6o/view
> C reproducer: https://pastebin.com/raw/kSxa6Yit
> Syzlang reproducer: https://pastebin.com/raw/2RMu8p6E
> 
> If you fix this issue, please add the following tag to the commit:
> Reported-by: Yuheng Shen mosesfonscqf75@gmail.com
> 
> ------------[ cut here ]------------
> WARNING: CPU: 5 PID: 29657 at arch/x86/kvm/mmu/tdp_mmu.c:46
> kvm_mmu_uninit_tdp_mmu+0xb9/0xf0

I wasn't able to reproduce to confirm, but this is more than likely fixed by
commit 3a0f64de479c ("KVM: x86/mmu: Don't advance iterator after restart due to yielding"),
which didn't land until 5.16-rc7.