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commitac64115a66upstream. The following program causes a kernel oops: #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <sys/ioctl.h> #include <linux/kvm.h> main() { int fd = open("/dev/kvm", O_RDWR); ioctl(fd, KVM_CHECK_EXTENSION, KVM_CAP_PPC_HTM); } This happens because when using the global KVM fd with KVM_CHECK_EXTENSION, kvm_vm_ioctl_check_extension() gets called with a NULL kvm argument, which gets dereferenced in is_kvmppc_hv_enabled(). Spotted while reading the code. Let's use the hv_enabled fallback variable, like everywhere else in this function. Fixes:23528bb21e("KVM: PPC: Introduce KVM_CAP_PPC_HTM") Signed-off-by: Greg Kurz <groug@kaod.org> Reviewed-by: David Gibson <david@gibson.dropbear.id.au> Reviewed-by: Thomas Huth <thuth@redhat.com> Signed-off-by: Paul Mackerras <paulus@ozlabs.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>