From: Timur Tabi <timur@freescale.com>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: <alan@lxorguk.ukuu.org.uk>, <linux-kernel@vger.kernel.org>,
<scottwood@freescale.com>, <akpm@linux-foundation.org>
Subject: Re: [PATCH] lib: introduce strdup_from_user
Date: Fri, 3 Jun 2011 13:34:51 -0500 [thread overview]
Message-ID: <4DE9294B.3040501@freescale.com> (raw)
In-Reply-To: <BANLkTimB2UanZA4wf=uBGcj=wKmDhCco=w@mail.gmail.com>
Alexey Dobriyan wrote:
> If mm is shared, data can or will change under you.
Ah, that's a good point. The only side-effect I can see of that is that it will
copy the string incorrectly, but it won't overwrite memory.
Would it be better if I did this:
str = kzalloc(max, GFP_KERNEL);
if (!str)
return ERR_PTR(-ENOMEM);
if (copy_from_user(str, ustr, max - 1)) {
kfree(str);
return ERR_PTR(-EFAULT);
}
return krealloc(str, strlen(str) + 1, GFP_KERNEL);
Maybe the krealloc() is overkill.
>> > How else is it supposed to know how much to allocate
>> > without using strlen first?
> I don't know.
> What I know is that your function doesn't guarantee NUL-termination.
That's a bug. The copy_from_user() should look like this:
if (copy_from_user(str, ustr, len - 1)) {
--
Timur Tabi
Linux kernel developer at Freescale
next prev parent reply other threads:[~2011-06-03 18:35 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 [this message]
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
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
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