Messages in this thread | | | Date | Mon, 10 Oct 2022 18:39:57 +0000 | From | Sean Christopherson <> | Subject | Re: [kbuild] arch/x86/kvm/x86.c:4988 kvm_arch_tsc_set_attr() warn: check for integer overflow 'offset' |
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On Mon, Oct 10, 2022, Dan Carpenter wrote: > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > head: 493ffd6605b2d3d4dc7008ab927dba319f36671f > commit: 828ca89628bfcb1b8f27535025f69dd00eb55207 KVM: x86: Expose TSC offset controls to userspace > config: x86_64-randconfig-m001-20221010 > compiler: gcc-11 (Debian 11.3.0-5) 11.3.0 > > If you fix the issue, kindly add following tag where applicable > | Reported-by: kernel test robot <lkp@intel.com> > | Reported-by: Dan Carpenter <dan.carpenter@oracle.com> > > smatch warnings: > arch/x86/kvm/x86.c:4988 kvm_arch_tsc_set_attr() warn: check for integer overflow 'offset' > > vim +/offset +4988 arch/x86/kvm/x86.c > > 828ca89628bfcb Oliver Upton 2021-09-16 4962 static int kvm_arch_tsc_set_attr(struct kvm_vcpu *vcpu, > 828ca89628bfcb Oliver Upton 2021-09-16 4963 struct kvm_device_attr *attr) > 828ca89628bfcb Oliver Upton 2021-09-16 4964 { > 828ca89628bfcb Oliver Upton 2021-09-16 4965 u64 __user *uaddr = (u64 __user *)(unsigned long)attr->addr; > 828ca89628bfcb Oliver Upton 2021-09-16 4966 struct kvm *kvm = vcpu->kvm; > 828ca89628bfcb Oliver Upton 2021-09-16 4967 int r; > 828ca89628bfcb Oliver Upton 2021-09-16 4968 > 828ca89628bfcb Oliver Upton 2021-09-16 4969 if ((u64)(unsigned long)uaddr != attr->addr) > 828ca89628bfcb Oliver Upton 2021-09-16 4970 return -EFAULT; > 828ca89628bfcb Oliver Upton 2021-09-16 4971 > 828ca89628bfcb Oliver Upton 2021-09-16 4972 switch (attr->attr) { > 828ca89628bfcb Oliver Upton 2021-09-16 4973 case KVM_VCPU_TSC_OFFSET: { > 828ca89628bfcb Oliver Upton 2021-09-16 4974 u64 offset, tsc, ns; > 828ca89628bfcb Oliver Upton 2021-09-16 4975 unsigned long flags; > 828ca89628bfcb Oliver Upton 2021-09-16 4976 bool matched; > 828ca89628bfcb Oliver Upton 2021-09-16 4977 > 828ca89628bfcb Oliver Upton 2021-09-16 4978 r = -EFAULT; > 828ca89628bfcb Oliver Upton 2021-09-16 4979 if (get_user(offset, uaddr)) > 828ca89628bfcb Oliver Upton 2021-09-16 4980 break; > 828ca89628bfcb Oliver Upton 2021-09-16 4981 > 828ca89628bfcb Oliver Upton 2021-09-16 4982 raw_spin_lock_irqsave(&kvm->arch.tsc_write_lock, flags); > 828ca89628bfcb Oliver Upton 2021-09-16 4983 > 828ca89628bfcb Oliver Upton 2021-09-16 4984 matched = (vcpu->arch.virtual_tsc_khz && > 828ca89628bfcb Oliver Upton 2021-09-16 4985 kvm->arch.last_tsc_khz == vcpu->arch.virtual_tsc_khz && > 828ca89628bfcb Oliver Upton 2021-09-16 4986 kvm->arch.last_tsc_offset == offset); > 828ca89628bfcb Oliver Upton 2021-09-16 4987 > 828ca89628bfcb Oliver Upton 2021-09-16 @4988 tsc = kvm_scale_tsc(vcpu, rdtsc(), vcpu->arch.l1_tsc_scaling_ratio) + offset; > > Smatch hates obvious user triggerable integer overflows... No checking > on offset.
This is ok, and even necessary, e.g. if the host TSC > guest TSC. Is there anything we can do in KVM to help Smatch avoid false positives? Or do you/Smatch already maintain a list of known false positives?
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