linux-kernel - Re: [PATCH v2 net-next 1/2] lib: introduce strncpy_from

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Message-ID: <20150828181141.6d974130@gandalf.local.home>
Date:	Fri, 28 Aug 2015 18:11:41 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Alexei Starovoitov <ast@...mgrid.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...nel.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Wang Nan <wangnan0@...wei.com>, He Kuang <hekuang@...wei.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 net-next 1/2] lib: introduce strncpy_from_unsafe()

On Fri, 28 Aug 2015 15:08:35 -0700
Alexei Starovoitov <ast@...mgrid.com> wrote:

> On 8/28/15 2:48 PM, Steven Rostedt wrote:
> >>   * On success, returns the length of the string (not including the trailing
> >> >+ * NUL).
> > I think it includes the NUL.
> 
> oops. yes. that was a copy paste from strncpy_from_user comment.
> trace_kprobe usage wants NUL to be counted, so I intended to have it
> counted, but that brings the question what should be the semantics.
> Should it be similar to strncpy_from_user (not counting NUL) or
> similar to strlen_user (counts NUL) ?
> imo counting NUL makes a little bit more sense, since when a user says
> strncpy_from_unsafe(..., ..., 32)
> and it returns 32 as the whole buffer was filled, it looks cleaner.
> Thoughts?
> 

I personally prefer counting the NUL. I've had issues in the past with
the strncpy_from_user() not counting it :-p

-- Steve
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