linux-kernel - RE: [PATCH] hyperv: a potential NULL pointer dereference

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Date:   Thu, 14 Mar 2019 14:56:59 +0000
From:   KY Srinivasan <kys@...rosoft.com>
To:     Kangjie Lu <kjlu@....edu>
CC:     "pakki001@....edu" <pakki001@....edu>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] hyperv: a potential NULL pointer dereference



> -----Original Message-----
> From: Kangjie Lu <kjlu@....edu>
> Sent: Wednesday, March 13, 2019 10:47 PM
> To: kjlu@....edu
> Cc: pakki001@....edu; KY Srinivasan <kys@...rosoft.com>; Haiyang Zhang
> <haiyangz@...rosoft.com>; Stephen Hemminger
> <sthemmin@...rosoft.com>; Sasha Levin <sashal@...nel.org>; Thomas
> Gleixner <tglx@...utronix.de>; Ingo Molnar <mingo@...hat.com>; Borislav
> Petkov <bp@...en8.de>; H. Peter Anvin <hpa@...or.com>; x86@...nel.org;
> linux-hyperv@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: [PATCH] hyperv: a potential NULL pointer dereference
> 
> In case alloc_page, the fix returns -ENOMEM to avoid the potential
> NULL pointer dereference.
> 
Thanks.

> Signed-off-by: Kangjie Lu <kjlu@....edu>
Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>

> ---
>  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);
> 
> --
> 2.17.1