4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Greg Kurz <groug@xxxxxxxx> commit ac64115a66c18c01745bbd3c47a36b124e5fd8c0 upstream. 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: 23528bb21ee2 ("KVM: PPC: Introduce KVM_CAP_PPC_HTM") Signed-off-by: Greg Kurz <groug@xxxxxxxx> Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx> Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/powerpc/kvm/powerpc.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -601,8 +601,7 @@ int kvm_vm_ioctl_check_extension(struct break; #endif case KVM_CAP_PPC_HTM: - r = cpu_has_feature(CPU_FTR_TM_COMP) && - is_kvmppc_hv_enabled(kvm); + r = cpu_has_feature(CPU_FTR_TM_COMP) && hv_enabled; break; default: r = 0;