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Subject: Re: [PATCH] hyperv: a potential NULL pointer dereference
To:     Kangjie Lu <kjlu@umn.edu>
Cc:     pakki001@umn.edu, "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Sasha Levin <sashal@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20190314054651.1315-1-kjlu@umn.edu>
From:   Mukesh Ojha <mojha@codeaurora.org>
Message-ID: <24cbb2df-6510-2ed8-deca-670ea934db68@codeaurora.org>
Date:   Wed, 20 Mar 2019 21:20:13 +0530
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On 3/14/2019 11:16 AM, Kangjie Lu wrote:
> In case alloc_page, the fix returns -ENOMEM to avoid the potential
> NULL pointer dereference.
>
> Signed-off-by: Kangjie Lu <kjlu@umn.edu>
> ---
>   arch/x86/hyperv/hv_init.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 7abb09e2eeb8..dfdb4ce1ae9c 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -102,9 +102,13 @@ static int hv_cpu_init(unsigned int cpu)
>   	u64 msr_vp_index;
>   	struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
>   	void **input_arg;
> +	struct page *pg;
>   
>   	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> -	*input_arg = page_address(alloc_page(GFP_KERNEL));
> +	pg = alloc_page(GFP_KERNEL);
> +	if (unlikely(!pg))
> +		return -ENOMEM;
> +	*input_arg = page_address(pg);
>   
>   	hv_get_vp_index(msr_vp_index);


Looks good to me.
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>


Thanks.
Mukesh


>