From: Sean Christopherson <seanjc@google.com>
To: Wanpeng Li <kernellwp@gmail.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
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>
Subject: Re: [PATCH v4 1/2] KVM: X86: Fix warning caused by stale emulation context
Date: Fri, 28 May 2021 00:28:02 +0000 [thread overview]
Message-ID: <YLA5Egyhy5uKDSxq@google.com> (raw)
In-Reply-To: <1622160097-37633-1-git-send-email-wanpengli@tencent.com>
On Thu, May 27, 2021, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@tencent.com>
>
> Reported by syzkaller:
>
> WARNING: CPU: 7 PID: 10526 at linux/arch/x86/kvm//x86.c:7621 x86_emulate_instruction+0x41b/0x510 [kvm]
> RIP: 0010:x86_emulate_instruction+0x41b/0x510 [kvm]
> Call Trace:
> kvm_mmu_page_fault+0x126/0x8f0 [kvm]
> vmx_handle_exit+0x11e/0x680 [kvm_intel]
> vcpu_enter_guest+0xd95/0x1b40 [kvm]
> kvm_arch_vcpu_ioctl_run+0x377/0x6a0 [kvm]
> kvm_vcpu_ioctl+0x389/0x630 [kvm]
> __x64_sys_ioctl+0x8e/0xd0
> do_syscall_64+0x3c/0xb0
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> Commit 4a1e10d5b5d8 ("KVM: x86: handle hardware breakpoints during emulation())
> adds hardware breakpoints check before emulation the instruction and parts of
> emulation context initialization, actually we don't have the EMULTYPE_NO_DECODE flag
> here and the emulation context will not be reused. Commit c8848cee74ff ("KVM: x86:
> set ctxt->have_exception in x86_decode_insn()) triggers the warning because it
> catches the stale emulation context has #UD, however, it is not during instruction
> decoding which should result in EMULATION_FAILED. This patch fixes it by moving
> the second part emulation context initialization into init_emulate_ctxt() and
> before hardware breakpoints check. The ctxt->ud will be dropped by a follow-up
> patch.
>
> syzkaller source: https://syzkaller.appspot.com/x/repro.c?x=134683fdd00000
>
> Reported-by: syzbot+71271244f206d17f6441@syzkaller.appspotmail.com
> Fixes: 4a1e10d5b5d8 (KVM: x86: handle hardware breakpoints during emulation)
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
Reviewed-by: Sean Christopherson <seanjc@google.com>
prev parent reply other threads:[~2021-05-28 0:28 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-28 0:01 [PATCH v4 1/2] KVM: X86: Fix warning caused by stale emulation context Wanpeng Li
2021-05-28 0:01 ` [PATCH v4 2/2] KVM: X86: Kill off ctxt->ud Wanpeng Li
2021-05-28 0:28 ` Sean Christopherson
2021-05-28 0:28 ` Sean Christopherson [this message]
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