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linux/arch/s390/include
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Claudio Imbrenda 496e0f706b KVM: s390: Fix unlikely NULL gmap dereference 
When creating a new vCPU, kvm_vm_ioctl_create_vcpu() will call
kvm_arch_vcpu_postcreate() after the file descriptor for the new vCPU
has been created. The new file descriptor has not been returned yet,
but a malicious userspace program could try to guess it.

If a malicious userspace program manages to start the newly created vCPU
before kvm_arch_vcpu_postcreate() is called, __vcpu_run() will try to
dereference vcpu->arch.gmap and trigger a NULL pointer dereference.

Fix this by adding a new field to struct kvm_vcpu_arch to keep track of
the initialization status of the vCPU. Refuse to run a vCPU that is not
fully initialized.

Fixes: dafd032a15 ("KVM: s390: move vcpu specific initalization to a later point")
Fixes: e38c884df9 ("KVM: s390: Switch to new gmap")
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20260803124040.126471-2-imbrenda@linux.ibm.com>
History 2026-08-03 15:39:05 +02:00
..
asm KVM: s390: Fix unlikely NULL gmap dereference 2026-08-03 15:39:05 +02:00
uapi/asm KVM: s390: vsie: Refactor handle_stfle 2026-06-12 15:13:27 +02:00