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Date:   Sat, 26 Oct 2019 17:24:58 +0300
From:   Dan Carpenter <dan.carpenter@oracle.com>
To:     zhanglin <zhang.lin16@zte.com.cn>
Cc:     davem@davemloft.net, ast@kernel.org, daniel@iogearbox.net,
        jakub.kicinski@netronome.com, hawk@kernel.org,
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        vivien.didelot@gmail.com, linyunsheng@huawei.com,
        natechancellor@gmail.com, arnd@arndb.de, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
        xue.zhihong@zte.com.cn, wang.yi59@zte.com.cn,
        jiang.xuexin@zte.com.cn
Subject: Re: [PATCH] net: Zeroing the structure ethtool_wolinfo in
 ethtool_get_wol()
Message-ID: <20191026142458.GJ23523@kadam>
References: <1572076456-12463-1-git-send-email-zhang.lin16@zte.com.cn>
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On Sat, Oct 26, 2019 at 03:54:16PM +0800, zhanglin wrote:
> memset() the structure ethtool_wolinfo that has padded bytes
> but the padded bytes have not been zeroed out.
> 
> Signed-off-by: zhanglin <zhang.lin16@zte.com.cn>
> ---
>  net/core/ethtool.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/net/core/ethtool.c b/net/core/ethtool.c
> index aeabc48..563a845 100644
> --- a/net/core/ethtool.c
> +++ b/net/core/ethtool.c
> @@ -1471,11 +1471,13 @@ static int ethtool_reset(struct net_device *dev, char __user *useraddr)
>  
>  static int ethtool_get_wol(struct net_device *dev, char __user *useraddr)
>  {
> -	struct ethtool_wolinfo wol = { .cmd = ETHTOOL_GWOL };
> +	struct ethtool_wolinfo wol;
>  

How did you detect that they weren't initialized?  Is this a KASAN
thing?

Most of the time GCC will zero out the padding bytes when you have an
initializer like this, but sometimes it just makes the intialization a
series of assignments which leaves the holes uninitialized.  I wish I
knew the rules so that I could check for it in Smatch.  Or even better,
I wish that there were an option to always zero the holes in this
situation...

regards,
dan carpenter