On 17/07/2019 14:44, Julien Thierry wrote: > Hi Zenghui, > > On 17/07/2019 13:20, Zenghui Yu wrote: >> We use "pmc->idx" and the "chained" bitmap to determine if the pmc is >> chained, in kvm_pmu_pmc_is_chained(). But idx might be uninitialized >> (and random) when we doing this decision, through a KVM_ARM_VCPU_INIT >> ioctl -> kvm_pmu_vcpu_reset(). And the test_bit() against this random >> idx will potentially hit a KASAN BUG [1]. >> >> Fix it by moving the assignment of idx before kvm_pmu_stop_counter(). >> >> [1] https://www.spinics.net/lists/kvm-arm/msg36700.html >> >> Fixes: 80f393a23be6 ("KVM: arm/arm64: Support chained PMU counters") >> Suggested-by: Andrew Murray <andrew.murray@xxxxxxx> >> Cc: Marc Zyngier <maz@xxxxxxxxxx> >> Signed-off-by: Zenghui Yu <yuzenghui@xxxxxxxxxx>> --- >> virt/kvm/arm/pmu.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c >> index 3dd8238..521bfdd 100644 >> --- a/virt/kvm/arm/pmu.c >> +++ b/virt/kvm/arm/pmu.c >> @@ -225,8 +225,8 @@ void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu) >> struct kvm_pmu *pmu = &vcpu->arch.pmu; >> >> for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) { >> - kvm_pmu_stop_counter(vcpu, &pmu->pmc[i]); >> pmu->pmc[i].idx = i; > > Yes, this is kind of a static property that should really be part of a > "kvm_pmu_vcpu_init()" or "kvm_pmu_vcpu_create()" and is not expected to > be modified across resets... > > There is no such function at the time and I'm unsure whether this > warrants creating that separate function (I would still suggest creating > it to make things clearer). Yup, that's pretty bad, now that you mention it. I'd be all for the introduction of kvm_pmu_vcpu_init(), given that we already have kvm_pmu_vcpu_destroy(). > >> + kvm_pmu_stop_counter(vcpu, &pmu->pmc[i]); > > Whatever other opinions are on splitting pmu_vcpu_init/reset, that > change makes sense and fixes the issue: > > Acked-by: Julien Thierry <julien.thierry@xxxxxxx> > >> } >> >> bitmap_zero(vcpu->arch.pmu.chained, ARMV8_PMU_MAX_COUNTER_PAIRS); >> > > Cheers, > Zenghui, could you please update your patch to take the above into account? Thanks, M. -- Jazz is not dead, it just smells funny... _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
