From: Wanpeng Li <kernellwp@gmail.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>
Subject: [PATCH v3 1/2] KVM: X86: Fix warning caused by stale emulation context
Date: Wed, 26 May 2021 22:01:18 -0700 [thread overview]
Message-ID: <1622091679-31683-1-git-send-email-wanpengli@tencent.com> (raw)
From: Wanpeng Li <wanpengli@tencent.com>
Reported by syzkaller:
WARNING: CPU: 7 PID: 10526 at /home/kernel/ssd/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 4a1e10d5b5d8c (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.
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>
---
v2 -> v3:
* squash ctxt->ud
v1 -> v2:
* move the second part emulation context initialization into init_emulate_ctxt()
arch/x86/kvm/x86.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bbc4e04..ae47b19 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7226,6 +7226,13 @@ static void init_emulate_ctxt(struct kvm_vcpu *vcpu)
BUILD_BUG_ON(HF_SMM_MASK != X86EMUL_SMM_MASK);
BUILD_BUG_ON(HF_SMM_INSIDE_NMI_MASK != X86EMUL_SMM_INSIDE_NMI_MASK);
+ ctxt->interruptibility = 0;
+ ctxt->have_exception = false;
+ ctxt->exception.vector = -1;
+ ctxt->perm_ok = false;
+
+ ctxt->ud = emulation_type & EMULTYPE_TRAP_UD;
+
init_decode_cache(ctxt);
vcpu->arch.emulate_regs_need_sync_from_vcpu = false;
}
@@ -7561,13 +7568,6 @@ int x86_decode_emulated_instruction(struct kvm_vcpu *vcpu, int emulation_type,
kvm_vcpu_check_breakpoint(vcpu, &r))
return r;
- ctxt->interruptibility = 0;
- ctxt->have_exception = false;
- ctxt->exception.vector = -1;
- ctxt->perm_ok = false;
-
- ctxt->ud = emulation_type & EMULTYPE_TRAP_UD;
-
r = x86_decode_insn(ctxt, insn, insn_len);
trace_kvm_emulate_insn_start(vcpu);
--
2.7.4
next reply other threads:[~2021-05-27 5:02 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-27 5:01 Wanpeng Li [this message]
2021-05-27 5:01 ` [PATCH v3 2/2] KVM: X86: Kill off ctxt->ud Wanpeng Li
2021-05-27 17:03 ` [PATCH v3 1/2] KVM: X86: Fix warning caused by stale emulation context Sean Christopherson
2021-05-27 22:53 ` Wanpeng Li
2021-05-27 23:03 ` Wanpeng Li
2021-05-27 23:46 ` Sean Christopherson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1622091679-31683-1-git-send-email-wanpengli@tencent.com \
--to=kernellwp@gmail.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=seanjc@google.com \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).