linux-kernel - Re: [PATCH linux-next] KVM: x86: don't forget vcpu_put() in kvm_arch_vcpu_ioctl_set

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Date:   Thu, 21 Dec 2017 12:02:26 +1100
From:   Stephen Rothwell <sfr@...b.auug.org.au>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Eric Biggers <ebiggers3@...il.com>, kvm@...r.kernel.org,
        rkrcmar@...hat.com, tianyu.lan@...el.com,
        christoffer.dall@...aro.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        Eric Biggers <ebiggers@...gle.com>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: [PATCH linux-next] KVM: x86: don't forget vcpu_put() in
 kvm_arch_vcpu_ioctl_set_sregs()

Hi Paolo,

On Thu, 21 Dec 2017 01:30:30 +0100 Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> On 21/12/2017 01:24, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@...gle.com>
> > 
> > Due to a bad merge resolution between commit f29810335965 ("KVM/x86:
> > Check input paging mode when cs.l is set") and commit b4ef9d4e8cb8
> > ("KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_ioctl_set_sregs"),
> > there is a case in kvm_arch_vcpu_ioctl_set_sregs() where vcpu_put() is
> > not called after vcpu_get().  Fix it.
> > 
> > Reported-by: syzbot <syzkaller@...glegroups.com>
> > Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> > ---
> >  arch/x86/kvm/x86.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index ea3a98196753..f4e8b5089b28 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -7624,7 +7624,7 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
> >  		goto out;
> >  
> >  	if (kvm_valid_sregs(vcpu, sregs))
> > -		return -EINVAL;
> > +		goto out;
> >  
> >  	apic_base_msr.data = sregs->apic_base;
> >  	apic_base_msr.host_initiated = true;
> >   
> 
> Thanks very much Eric, that was fast!  Adding Stephen and the linux-next
> mailing list to Cc.  Adding the kvm/master tree has already paid off.

I will apply that as a merge fix patch for the kvm tree merge from
today.  Please remember to apply it if/when you merge the master branch
into your linux-next branch or when these trees meet in Linus' tree.
-- 
Cheers,
Stephen Rothwell