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

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Date:	Wed, 27 Jan 2016 11:50:10 -0800
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Eric Dumazet <eric.dumazet@...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 Tue, Jan 26, 2016 at 6:23 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Tue, 2016-01-26 at 15:12 -0800, Cong Wang wrote:
>> On Tue, Jan 26, 2016 at 2:55 PM, Julian Calaby <julian.calaby@...il.com> wrote:
>> > Hi Cong,
>> >
>> > On Wed, Jan 27, 2016 at 4:53 AM, Cong Wang <xiyou.wangcong@...il.com> wrote:
>> >
>> > A commit message would be nice. A brief rundown of how this is called
>> > from userspace would be nice (I'm talking a single sentence here, e.g.
>> > "this is allocated when submitting a nfc packet") and what issue
>> > __GFP_NOWARN is fixing. (I'm guessing log spam due to allocation
>> > failures.)
>> >
>>
>> I thought it is obvious. ;) Keep in mind that $subject is one part of commit
>> message too, so there is a commit message although very short.
>>
>> I will add it.
>
>
> BTW, kzalloc() is useless here, since it is followed by
>
> if (memcpy_from_msg(msg_data, msg, len)) {

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.

>
> Also, this file seems to have two spots with the same problem,
> in nfc_llcp_send_ui_frame() & nfc_llcp_send_i_frame()
>

Ah, yes, I missed nfc_llcp_send_i_frame().