Re: [PATCH 1/2] LoongArch: KVM: Make kvm_get_vcpu_by_cpuid() more robust

[Huacai Chen]

On Mon, Mar 23, 2026 at 11:16 AM Bibo Mao <maobibo@xxxxxxxxxxx> wrote:
>
>
>
> On 2026/3/22 下午9:53, Huacai Chen wrote:
> > kvm_get_vcpu_by_cpuid() takes a cpuid parameter whose type is int, so
> > cpuid can be negative. Let kvm_get_vcpu_by_cpuid() return NULL for this
> > case so as to make it more robust.
> >
> > This fix an out-of-bounds access to kvm_arch::phyid_map::phys_map[].
> >
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Fixes: 73516e9da512adc ("LoongArch: KVM: Add vcpu mapping from physical cpuid")
> > Reported-by: Aurelien Jarno <aurel32@xxxxxxxxxx>
> > Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1131431
> > Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
> > ---
> >   arch/loongarch/kvm/vcpu.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
> > index 8ffd50a470e6..831f381a8fd1 100644
> > --- a/arch/loongarch/kvm/vcpu.c
> > +++ b/arch/loongarch/kvm/vcpu.c
> > @@ -588,6 +588,9 @@ struct kvm_vcpu *kvm_get_vcpu_by_cpuid(struct kvm *kvm, int cpuid)
> >   {
> >       struct kvm_phyid_map *map;
> >
> > +     if (cpuid < 0)
> > +             return NULL;
> > +
> >       if (cpuid >= KVM_MAX_PHYID)
> >               return NULL;
> >
> >
>
> if (cpuid < 0 || cpuid >= KVM_MAX_PHYID)?
> however both are OK for me.
I use a similar style as kvm_get_vcpu_by_id(). :)

But there is another warning which can't be solved by this series (and
I doubt whether it can be solved unless revert 01a8e68396a6d51f5b).
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1131431

Huacai

>
> Reviewed-by: Bibo Mao <maobibo@xxxxxxxxxxx>
>