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Date:   Tue, 01 Jan 2019 09:51:53 +0100
Message-ID: <s5hsgyciwuu.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     " huang.zijiang " <huang.zijiang@zte.com.cn>
Cc:     <perex@perex.cz>, <w@1wt.eu>, <alsa-devel@alsa-project.org>,
        <colin.king@canonical.com>, <keescook@chromium.org>,
        <linux-kernel@vger.kernel.org>, <wang.yi59@zte.com.cn>,
        <xue.zhihong@zte.com.cn>
Subject: Re: [PATCH] sound:emu10k1:Use kmemdup instead of duplicating its function
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References: <1545640968-42357-1-git-send-email-huang.zijiang@zte.com.cn>
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On Mon, 24 Dec 2018 09:42:48 +0100,
 huang.zijiang  wrote:
> 
> From: "huang.zijiang" <huang.zijiang@zte.com.cn>
> 
> kmemdup has implemented the function that kmalloc() and memcpy().
> 
> Signed-off-by: huang.zijiang <huang.zijiang@zte.com.cn>
> ---
>  sound/pci/emu10k1/emufx.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/sound/pci/emu10k1/emufx.c b/sound/pci/emu10k1/emufx.c
> index 6ebe817..b4fe4c5 100644
> --- a/sound/pci/emu10k1/emufx.c
> +++ b/sound/pci/emu10k1/emufx.c
> @@ -671,10 +671,9 @@ static unsigned int *copy_tlv(const unsigned int __user *_tlv, bool in_kernel)
>  		return NULL;
>  	if (data[1] >= MAX_TLV_SIZE)
>  		return NULL;
> -	tlv = kmalloc(data[1] + sizeof(data), GFP_KERNEL);
> +	tlv =  kmemdup(data, data[1] + sizeof(data), GFP_KERNEL);
>  	if (!tlv)
>  		return NULL;
> -	memcpy(tlv, data, sizeof(data));

These changes are not equivalent, and rather dangerous, unfortunately.
The memcpy() performs only for sizeof(data), and in this case, it's
not the same size as the allocation above.


thanks,

Takashi