linux-kernel - Re: [RFC 01/12] KVM: arm/arm64: Avoid multiple dist->spis kfree

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 19 Mar 2018 13:46:15 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Eric Auger <eric.auger@...hat.com>, eric.auger.pro@...il.com,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, cdall@...nel.org,
        peter.maydell@...aro.org
Cc:     andre.przywara@....com, drjones@...hat.com, wei@...hat.com
Subject: Re: [RFC 01/12] KVM: arm/arm64: Avoid multiple dist->spis kfree

On 19/03/18 09:20, Eric Auger wrote:
> in case kvm_vgic_map_resources() fails, typically if the vgic
> distributor is not defined, __kvm_vgic_destroy will be called
> several times. Indeed kvm_vgic_map_resources() is called on
> first vcpu run. As a result dist->spis is freeed twice and on
> the second time it causes a "kernel BUG at mm/slub.c:3912!"
> 
> This patch avoids freeing dist->spis twice.
> 
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> ---
>  virt/kvm/arm/vgic/vgic-init.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
> index 743ca5c..38fd5f1 100644
> --- a/virt/kvm/arm/vgic/vgic-init.c
> +++ b/virt/kvm/arm/vgic/vgic-init.c
> @@ -324,7 +324,10 @@ static void kvm_vgic_dist_destroy(struct kvm *kvm)
>  	dist->ready = false;
>  	dist->initialized = false;
>  
> -	kfree(dist->spis);
> +	if (dist->spis) {
> +		kfree(dist->spis);
> +		dist->spis = NULL;
> +	}

Given that kfree(NULL) is always a valid thing to do, you could write
the same thing just as

	dist-> spis = NULL;

without any test.

>  	dist->nr_spis = 0;
>  
>  	if (vgic_supports_direct_msis(kvm))
> 

You also may want to add a Fixes tag to it.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...