netdev - Re: [PATCH RESEND net] nfc: use GFP_USER for user-controlled kmalloc

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Date:	Wed, 27 Jan 2016 13:05:52 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Cong Wang <xiyou.wangcong@...il.com>
Cc:	Julian Calaby <julian.calaby@...il.com>,
	netdev <netdev@...r.kernel.org>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	Lauro Ramos Venancio <lauro.venancio@...nbossa.org>,
	Aloisio Almeida Jr <aloisio.almeida@...nbossa.org>,
	Samuel Ortiz <sameo@...ux.intel.com>
Subject: Re: [PATCH RESEND net] nfc: use GFP_USER for user-controlled kmalloc

On Wed, 2016-01-27 at 11:50 -0800, Cong Wang wrote:

> Hmm? I think nfc_llcp_send_ui_frame() needs to do some fragmention
> with this temporary memory, or you are saying msg_iter has some
> API available to seek the pointer? Even if so, it doesn't look like
> suitable for -stable.
> 

memcpy_from_msg(msg_data, msg, len) will overwrite the msg_data with len
bytes, or return an error.

So prior msg_data content does not matter.

kzalloc() before a memset() or memcpy() sounds defensive programming,
kmalloc() is a bit faster.