KVM: PPC: Fix oops when checking KVM_CAP_PPC_HTM
authorGreg Kurz <groug@kaod.org>
Thu, 14 Sep 2017 21:56:25 +0000 (23:56 +0200)
committerPaul Mackerras <paulus@ozlabs.org>
Sat, 14 Oct 2017 00:32:53 +0000 (11:32 +1100)
commitac64115a66c18c01745bbd3c47a36b124e5fd8c0
treeb58e717d09ba7479189c8ee37f8d819f38348f51
parent8a5776a5f49812d29fe4b2d0a2d71675c3facf3f
KVM: PPC: Fix oops when checking KVM_CAP_PPC_HTM

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")
Cc: stable@vger.kernel.org # v4.7+
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>
arch/powerpc/kvm/powerpc.c