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From:   Jiasheng Jiang <jiasheng@iscas.ac.cn>
To:     gregkh@linuxfoundation.org
Cc:     stephen@networkplumber.org, kys@microsoft.com,
        haiyangz@microsoft.com, sthemmin@microsoft.com, wei.liu@kernel.org,
        decui@microsoft.com, davem@davemloft.net, kuba@kernel.org,
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        linux-hyperv@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
        Jiasheng Jiang <jiasheng@iscas.ac.cn>
Subject: Re: [PATCH] hv_netvsc: Add check for kvmalloc_array
Date:   Mon, 14 Mar 2022 15:33:49 +0800
Message-Id: <20220314073349.2501022-1-jiasheng@iscas.ac.cn>
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On Fri, Mar 11, 2022 at 02:43:48PM +0800, Greg KH wrote:
>> As the potential failure of the kvmalloc_array(),
>> it should be better to check and restore the 'data'
>> if fails in order to avoid the dereference of the
>> NULL pointer.
>> 
>> Fixes: 6ae746711263 ("hv_netvsc: Add per-cpu ethtool stats for netvsc")
>> Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
>> ---
>>  drivers/net/hyperv/netvsc_drv.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>> 
>> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
>> index 3646469433b1..018c4a5f6f44 100644
>> --- a/drivers/net/hyperv/netvsc_drv.c
>> +++ b/drivers/net/hyperv/netvsc_drv.c
>> @@ -1587,6 +1587,12 @@ static void netvsc_get_ethtool_stats(struct net_device *dev,
>>  	pcpu_sum = kvmalloc_array(num_possible_cpus(),
>>  				  sizeof(struct netvsc_ethtool_pcpu_stats),
>>  				  GFP_KERNEL);
>> +	if (!pcpu_sum) {
>> +		for (j = 0; j < i; j++)
>> +			data[j] = 0;
>> +		return;
>> +	}
> 
>How did you test this to verify it is correct?

Thanks, I have tested the patch by kernel_patch_verify,
and all the tests are passed.

Jiang