In the Linux kernel, the following vulnerability has been resolved:

KVM: s390: vsie: fix race during shadow creation

Right now it is possible to see gmap->private being zero in
kvm_s390_vsie_gmap_notifier resulting in a crash. This is due to the
fact that we add gmap->private == kvm after creation:

static int acquire_gmap_shadow(struct kvm_vcpu *vcpu,
struct vsie_page *vsie_page)
{
[...]
gmap = gmap_shadow(vcpu->arch.gmap, asce, edat);
if (IS_ERR(gmap))
return PTR_ERR(gmap);
gmap->private = vcpu->kvm;

Let children inherit the private field of the parent.

References

• https://nvd.nist.gov/vuln/detail/CVE-2023-52639
• https://git.kernel.org/stable/c/28bb27824f25f36e5f80229a358d66ee09244082
• https://git.kernel.org/stable/c/5df3b81a567eb565029563f26f374ae3803a1dfc
• https://git.kernel.org/stable/c/f5572c0323cf8b4f1f0618178648a25b8fb8a380
• https://git.kernel.org/stable/c/fe752331d4b361d43cfd0b89534b4b2176057c32