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
