linux-kernel - Re: [patch] kvm: suppress KVM_SET_GSI

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Date:   Tue, 13 Feb 2018 16:14:04 +0100
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     David Rientjes <rientjes@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [patch] kvm: suppress KVM_SET_GSI_ROUTING allocation failure



On 02/08/2018 10:35 PM, David Rientjes wrote:
> The KVM_SET_GSI_ROUTING ioctl does a vmalloc() of
> sizeof(struct kvm_irq_routing_entry) multiplied by a user-supplied value.
> This can be up to 4096 entries on architectures such as arm64 and s390
> (and the upper bound may be increased on s390 eventually).
> 
> This can produce a vmalloc allocation failure warning:
> 
[...]
>  kvm_vm_ioctl+0x910/0x15e0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4153

                                                                       ^^^^^

> @@ -3063,7 +3063,8 @@ static long kvm_vm_ioctl(struct file *filp,

      ^^^^^


Are you sure that you got the right vmalloc?


>  			goto out;
>  		if (routing.nr) {
>  			r = -ENOMEM;
> -			entries = vmalloc(routing.nr * sizeof(*entries));
> +			entries = __vmalloc(routing.nr * sizeof(*entries),
> +					GFP_KERNEL | __GFP_NOWARN, PAGE_KERNEL);
>  			if (!entries)
>  				goto out;
>  			r = -EFAULT;
>