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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id mw1sm5438635ejb.1.2020.10.26.02.07.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Oct 2020 02:07:28 -0700 (PDT) From: Vitaly Kuznetsov To: Peter Xu , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: peterx@redhat.com, Sean Christopherson , Paolo Bonzini , Steffen Dirkwinkel Subject: Re: [PATCH 2/2] KVM: X86: Fix null pointer reference for KVM_GET_MSRS In-Reply-To: <20201025185334.389061-3-peterx@redhat.com> References: <20201025185334.389061-1-peterx@redhat.com> <20201025185334.389061-3-peterx@redhat.com> Date: Mon, 26 Oct 2020 10:07:27 +0100 Message-ID: <871rhl2w4w.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Xu writes: > kvm_msr_ignored_check() could trigger a null pointer reference 'dereference' but I'd also clarify that 'vcpu' is NULL. > 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 Fixes: 12bc2132b15e ("KVM: X86: Do the same ignore_msrs check for feature msrs") please (checkpatch.pl should've complained I guess) > Reported-by: Steffen Dirkwinkel > Signed-off-by: Peter Xu > --- > 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); I would've preserved vcpu version for non-gloal cases, e.g. if (report_ignored_msrs) { if (vcpu) vcpu_unimpl(vcpu, "ignored %s: 0x%x data 0x%llx\n", op, msr, data); else kvm_pr_unimpl("ignored %s: 0x%x data 0x%llx\n", op, msr, data); } > /* Mask the error */ > return 0; > } else { -- Vitaly