linux-kernel - Re: [PATCH] lib: introduce strdup_from

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4DE9294B.3040501@freescale.com>
Date:	Fri, 3 Jun 2011 13:34:51 -0500
From:	Timur Tabi <timur@...escale.com>
To:	Alexey Dobriyan <adobriyan@...il.com>
CC:	<alan@...rguk.ukuu.org.uk>, <linux-kernel@...r.kernel.org>,
	<scottwood@...escale.com>, <akpm@...ux-foundation.org>
Subject: Re: [PATCH] lib: introduce strdup_from_user

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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/