* Coverity: emulator_leave_smm(): Error handling issues
@ 2022-12-01 16:25 coverity-bot
2022-12-01 18:18 ` Sean Christopherson
0 siblings, 1 reply; 3+ messages in thread
From: coverity-bot @ 2022-12-01 16:25 UTC (permalink / raw)
To: Paolo Bonzini
Cc: Sean Christopherson, x86, Maxim Levitsky, linux-kernel,
Borislav Petkov, Ingo Molnar, H. Peter Anvin, Thomas Gleixner,
kvm, Dave Hansen, Gustavo A. R. Silva, linux-next,
linux-hardening
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
such, or teach the Coverity rules to be smarter. If not, please make
sure fixes get into linux-next. :) For patches fixing this, please
include these lines (but double-check the "Fixes" first):
Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
Addresses-Coverity-ID: 1527763 ("Error handling issues")
Fixes: 1d0da94cdafe ("KVM: x86: do not go through ctxt->ops when emulating rsm")
Thanks for your attention!
--
Coverity-bot
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: Coverity: emulator_leave_smm(): Error handling issues 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 0 siblings, 1 reply; 3+ messages in thread From: Sean Christopherson @ 2022-12-01 18:18 UTC (permalink / raw) To: coverity-bot Cc: Paolo Bonzini, x86, Maxim Levitsky, linux-kernel, Borislav Petkov, Ingo Molnar, H. Peter Anvin, Thomas Gleixner, kvm, Dave Hansen, Gustavo A. R. Silva, linux-next, linux-hardening 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... diff --git a/arch/x86/kvm/smm.c b/arch/x86/kvm/smm.c index a9c1c2af8d94..621e39689bff 100644 --- a/arch/x86/kvm/smm.c +++ b/arch/x86/kvm/smm.c @@ -601,8 +601,9 @@ int emulator_leave_smm(struct x86_emulate_ctxt *ctxt) /* Zero CR4.PCIDE before CR0.PG. */ cr4 = kvm_read_cr4(vcpu); - if (cr4 & X86_CR4_PCIDE) - kvm_set_cr4(vcpu, cr4 & ~X86_CR4_PCIDE); + if (cr4 & X86_CR4_PCIDE && + WARN_ON_ONCE(kvm_set_cr4(vcpu, cr4 & ~X86_CR4_PCIDE))) + return X86EMUL_UNHANDLEABLE; /* A 32-bit code segment is required to clear EFER.LMA. */ memset(&cs_desc, 0, sizeof(cs_desc)); @@ -614,8 +615,9 @@ int emulator_leave_smm(struct x86_emulate_ctxt *ctxt) /* For the 64-bit case, this will clear EFER.LMA. */ cr0 = kvm_read_cr0(vcpu); - if (cr0 & X86_CR0_PE) - kvm_set_cr0(vcpu, cr0 & ~(X86_CR0_PG | X86_CR0_PE)); + if (cr0 & X86_CR0_PE && + WARN_ON_ONCE(kvm_set_cr0(vcpu, cr0 & ~(X86_CR0_PG | X86_CR0_PE)))) + return X86EMUL_UNHANDLEABLE; #ifdef CONFIG_X86_64 if (guest_cpuid_has(vcpu, X86_FEATURE_LM)) { @@ -623,12 +625,14 @@ int emulator_leave_smm(struct x86_emulate_ctxt *ctxt) /* Clear CR4.PAE before clearing EFER.LME. */ cr4 = kvm_read_cr4(vcpu); - if (cr4 & X86_CR4_PAE) - kvm_set_cr4(vcpu, cr4 & ~X86_CR4_PAE); + if ((cr4 & X86_CR4_PAE && + WARN_ON_ONCE(kvm_set_cr4(vcpu, cr4 & ~X86_CR4_PAE))) + return X86EMUL_UNHANDLEABLE; /* And finally go back to 32-bit mode. */ efer = 0; - kvm_set_msr(vcpu, MSR_EFER, efer); + if (WARN_ON_ONCE(kvm_set_msr(vcpu, MSR_EFER, efer))) + return X86EMUL_UNHANDLEABLE; } #endif ^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: Coverity: emulator_leave_smm(): Error handling issues 2022-12-01 18:18 ` Sean Christopherson @ 2022-12-01 23:22 ` Kees Cook 0 siblings, 0 replies; 3+ messages in thread From: Kees Cook @ 2022-12-01 23:22 UTC (permalink / raw) To: Sean Christopherson Cc: Paolo Bonzini, x86, Maxim Levitsky, linux-kernel, Borislav Petkov, Ingo Molnar, H. Peter Anvin, Thomas Gleixner, kvm, Dave Hansen, Gustavo A. R. Silva, linux-next, linux-hardening 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 ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-12-01 23:22 UTC | newest] Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 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
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