linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Alexey Dobriyan <adobriyan@gmail.com>
To: Scott Wood <scottwood@freescale.com>
Cc: Timur Tabi <timur@freescale.com>,
	alan@lxorguk.ukuu.org.uk, linux-kernel@vger.kernel.org,
	akpm@linux-foundation.org
Subject: Re: [PATCH] lib: introduce strdup_from_user
Date: Fri, 3 Jun 2011 22:12:37 +0300	[thread overview]
Message-ID: <BANLkTikmVncMdJhK0Hi6uWeiE_S9TtdhTQ@mail.gmail.com> (raw)
In-Reply-To: <20110603135303.0800e4a7@schlenkerla.am.freescale.net>

On Fri, Jun 3, 2011 at 9:53 PM, Scott Wood <scottwood@freescale.com> wrote:
> On Fri, 3 Jun 2011 21:39:28 +0300
> Alexey Dobriyan <adobriyan@gmail.com> wrote:
>
>> On Fri, Jun 3, 2011 at 9:34 PM, Timur Tabi <timur@freescale.com> wrote:
>> > Would it be better if I did this:
>>
>> The point is data should cross kernelspace/userspace boundary only once.
>>
>
> Why does it matter, as long as it doesn't hurt the kernel if userspace
> plays games (i.e. take care of the NUL termination), and it's not a
> performance problem?

Because now you're lucky C strings are NUL-terminated.
If this "idiom" applies to some other case like "validate + copy",
we have a bug.

We copy data to kernelspace THEN validate or copy or whatever.
This is obviously correct and safe.

  parent reply	other threads:[~2011-06-03 19:12 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-03 16:45 [PATCH] lib: introduce strdup_from_user Timur Tabi
2011-06-03 17:45 ` Alexey Dobriyan
2011-06-03 18:22   ` Timur Tabi
2011-06-03 18:26     ` Alexey Dobriyan
2011-06-03 18:34       ` Timur Tabi
2011-06-03 18:39         ` Alexey Dobriyan
2011-06-03 18:41           ` Timur Tabi
2011-06-03 18:47             ` Alexey Dobriyan
2011-06-03 18:54               ` Timur Tabi
2011-06-03 18:53           ` Scott Wood
2011-06-03 18:57             ` Timur Tabi
2011-06-03 19:12             ` Alexey Dobriyan [this message]
2011-06-03 19:31               ` Scott Wood
2011-06-03 22:41               ` Al Viro
2011-06-03 18:37       ` Scott Wood
2011-06-03 21:58   ` Alan Cox

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=BANLkTikmVncMdJhK0Hi6uWeiE_S9TtdhTQ@mail.gmail.com \
    --to=adobriyan@gmail.com \
    --cc=akpm@linux-foundation.org \
    --cc=alan@lxorguk.ukuu.org.uk \
    --cc=linux-kernel@vger.kernel.org \
    --cc=scottwood@freescale.com \
    --cc=timur@freescale.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).