linux-kernel - Re: [PATCH] KVM: fix an error code in kvm_create

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Date: Fri, 14 Jun 2024 08:00:54 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Yi Wang <foxywang@...cent.com>, Paolo Bonzini <pbonzini@...hat.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] KVM: fix an error code in kvm_create_vm()

On Thu, Jun 13, 2024 at 04:50:48PM -0700, Sean Christopherson wrote:
> On Thu, Jun 13, 2024, Dan Carpenter wrote:
> > This error path used to return -ENOMEM from the where r is initialized
> > at the top of the function.  But a new "r = kvm_init_irq_routing(kvm);"
> > was introduced in the middle of the function so now the error code is
> > not set and it eventually leads to a NULL dereference.  Set the error
> > code back to -ENOMEM.
> > 
> > Fixes: fbe4a7e881d4 ("KVM: Setup empty IRQ routing when creating a VM")
> > Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> > ---
> >  virt/kvm/kvm_main.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index 07ec9b67a202..ea7e32d722c9 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -1212,8 +1212,10 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)
> >  	for (i = 0; i < KVM_NR_BUSES; i++) {
> >  		rcu_assign_pointer(kvm->buses[i],
> >  			kzalloc(sizeof(struct kvm_io_bus), GFP_KERNEL_ACCOUNT));
> > -		if (!kvm->buses[i])
> > +		if (!kvm->buses[i]) {
> > +			r = -ENOMEM;
> >  			goto out_err_no_arch_destroy_vm;
> > +		}
> >  	}
> 
> Drat.  Any objection to tweaking this slightly to guard against similar bugs in
> the future?  If not, I'll apply+push the below.

No objections from me.  :)

regards,
dan carpenter