From: Kees Cook <keescook@chromium.org>
To: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
x86@kernel.org, Maxim Levitsky <mlevitsk@redhat.com>,
linux-kernel@vger.kernel.org, Borislav Petkov <bp@alien8.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
kvm@vger.kernel.org, Dave Hansen <dave.hansen@linux.intel.com>,
"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
linux-next@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: Coverity: emulator_leave_smm(): Error handling issues
Date: Thu, 1 Dec 2022 15:22:46 -0800 [thread overview]
Message-ID: <202212011522.0A318649@keescook> (raw)
In-Reply-To: <Y4jwBahPrkwOI3w9@google.com>
On Thu, Dec 01, 2022 at 06:18:45PM +0000, Sean Christopherson wrote:
> On Thu, Dec 01, 2022, coverity-bot wrote:
> > Hello!
> >
> > This is an experimental semi-automated report about issues detected by
> > Coverity from a scan of next-20221201 as part of the linux-next scan project:
> > https://scan.coverity.com/projects/linux-next-weekly-scan
> >
> > You're getting this email because you were associated with the identified
> > lines of code (noted below) that were touched by commits:
> >
> > Wed Nov 9 12:31:18 2022 -0500
> > 1d0da94cdafe ("KVM: x86: do not go through ctxt->ops when emulating rsm")
> >
> > Coverity reported the following:
> >
> > *** CID 1527763: Error handling issues (CHECKED_RETURN)
> > arch/x86/kvm/smm.c:631 in emulator_leave_smm()
> > 625 cr4 = kvm_read_cr4(vcpu);
> > 626 if (cr4 & X86_CR4_PAE)
> > 627 kvm_set_cr4(vcpu, cr4 & ~X86_CR4_PAE);
> > 628
> > 629 /* And finally go back to 32-bit mode. */
> > 630 efer = 0;
> > vvv CID 1527763: Error handling issues (CHECKED_RETURN)
> > vvv Calling "kvm_set_msr" without checking return value (as is done elsewhere 5 out of 6 times).
> > 631 kvm_set_msr(vcpu, MSR_EFER, efer);
> > 632 }
> > 633 #endif
> > 634
> > 635 /*
> > 636 * Give leave_smm() a chance to make ISA-specific changes to the vCPU
> >
> > If this is a false positive, please let us know so we can mark it as
>
> It's not a false positive per se, but absent a KVM bug the call can never fail.
> Ditto for the kvm_set_cr{0,4}() calls above. That said, I'm tempted to "fix"
> these since we've had bugs related to this code in the past. This doesn't seem
> too ugly...
Yeah, that's what I've done with similar cases. "This should be
impossible" get a WARN_ONCE and fail gracefully.
-Kees
--
Kees Cook
prev parent reply other threads:[~2022-12-01 23:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-01 16:25 Coverity: emulator_leave_smm(): Error handling issues coverity-bot
2022-12-01 18:18 ` Sean Christopherson
2022-12-01 23:22 ` Kees Cook [this message]
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