linux-kernel - Re: [PATCH v2] powerpc: kvm: powerpc: fix information leak to userland

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Date:	Sat, 30 Oct 2010 12:16:57 -0700
From:	Alexander Graf <agraf@...e.de>
To:	Vasiliy Kulikov <segooon@...il.com>
Cc:	kernel-janitors@...r.kernel.org, Avi Kivity <avi@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>, kvm-ppc@...r.kernel.org,
	kvm@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] powerpc: kvm: powerpc: fix information leak to userland


On 30.10.2010, at 11:55, Vasiliy Kulikov wrote:

> Structure kvm_ppc_pvinfo is copied to userland with "flags" and "pad"
> fields unitialized.  It leads to leaking of contents of kernel stack
> memory.  We have to initialize them to zero.
> 
> In patch v1 Jan Kiszka suggested to fill reserved fields with zeros
> instead of memset'ting the whole struct.  It makes sense as these
> fields are explicitly marked as padding.  No more fields need zeroing.
> 
> Signed-off-by: Vasiliy Kulikov <segooon@...il.com>
> ---
> arch/powerpc/kvm/powerpc.c |    2 ++
> 1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 2f87a16..5962336 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -604,6 +604,8 @@ static int kvm_vm_ioctl_get_pvinfo(struct kvm_ppc_pvinfo *pvinfo)
> 	pvinfo->hcall[1] = inst_ori | (KVM_SC_MAGIC_R0 & inst_imm_mask);
> 	pvinfo->hcall[2] = inst_sc;
> 	pvinfo->hcall[3] = inst_nop;
> +	pvinfo->flags = 0;
> +	memset(&pvinfo->pad, 0, sizeof(pvinfo->pad));

This should only be memset(pvinfo->pad), no? It's an array after all which automatically translates to a pointer when referenced.

Alex

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