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Date: Sat, 14 Oct 2017 12:23:37 +1100
From: Paul Mackerras <paulus@ozlabs.org>
To: Greg Kurz <groug@kaod.org>
Cc: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org,
 David Gibson <david@gibson.dropbear.id.au>,
 Sam Bobroff <sam.bobroff@au1.ibm.com>,
 Paolo Bonzini <pbonzini@redhat.com>, linuxppc-dev@lists.ozlabs.org,
 stable@vger.kernel.org
Subject: Re: [PATCH] KVM: PPC: fix oops when checking KVM_CAP_PPC_HTM
Message-ID: <20171014012337.GB26120@fergus.ozlabs.ibm.com>
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On Thu, Sep 14, 2017 at 11:56:25PM +0200, Greg Kurz wrote:
> 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>

Thanks, applied to my kvm-ppc-fixes branch.

Paul.