linux-kernel - [PATCH 2/2] KVM: X86: Fix null pointer reference for KVM_GET

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Message-Id: <20201025185334.389061-3-peterx@redhat.com>
Date:   Sun, 25 Oct 2020 14:53:34 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>, peterx@...hat.com,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Steffen Dirkwinkel <kernel-bugs@...ffen.cc>
Subject: [PATCH 2/2] KVM: X86: Fix null pointer reference for KVM_GET_MSRS

kvm_msr_ignored_check() could trigger a null pointer reference if ignore_msrs=Y
and report_ignore_msrs=Y when try to fetch an invalid feature msr using the
global KVM_GET_MSRS.  Degrade the error report to not rely on vcpu since that
information (index, rip) is not as important as msr index/data after all.

Fixes: 12bc2132b15e0a96
Reported-by: Steffen Dirkwinkel <kernel-bugs@...ffen.cc>
Signed-off-by: Peter Xu <peterx@...hat.com>
---
 arch/x86/kvm/x86.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ce856e0ece84..5993fbd6d2c5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -259,8 +259,8 @@ static int kvm_msr_ignored_check(struct kvm_vcpu *vcpu, u32 msr,
 
 	if (ignore_msrs) {
 		if (report_ignored_msrs)
-			vcpu_unimpl(vcpu, "ignored %s: 0x%x data 0x%llx\n",
-				    op, msr, data);
+			kvm_pr_unimpl("ignored %s: 0x%x data 0x%llx\n",
+				      op, msr, data);
 		/* Mask the error */
 		return 0;
 	} else {
-- 
2.26.2