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KVM: PPC: Fix oops when checking KVM_CAP_PPC_HTM

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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")
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>
This commit is contained in:
Greg Kurz 2017-09-14 23:56:25 +02:00 committed by Paul Mackerras
parent 8a5776a5f4
commit ac64115a66
1 changed files with 1 additions and 2 deletions
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3
arch/powerpc/kvm/powerpc.c
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@ -644,8 +644,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
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;