linux-kernel - Re: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of attacking

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: <alpine.DEB.2.00.1011191156470.19579@asgard.lang.hm>
Date:	Fri, 19 Nov 2010 11:58:20 -0800 (PST)
From:	david@...g.hm
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	Marcus Meissner <meissner@...e.de>,
	linux-kernel@...r.kernel.org, tj@...nel.org,
	akpm@...ux-foundation.org, hpa@...or.com, mingo@...e.hu, w@....eu,
	alan@...rguk.ukuu.org.uk
Subject: Re: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of
 attacking

On Fri, 19 Nov 2010, Linus Torvalds wrote:

> On Fri, Nov 19, 2010 at 11:19 AM, Sarah Sharp
> <sarah.a.sharp@...ux.intel.com> wrote:
>>
>> .config and dmesg are attached.  The box is running klogd 1.5.5ubuntu3
>> (from Jaunty).  Yes, I know that's old.  I read the bit in the commit
>> about changing the permissions of kallsyms after boot, but if I can't
>> boot that doesn't help.  Perhaps this can be made a configuration
>> option?
>
> It's not worth a config option.
>
> If it actually breaks user-space, I think we should just revert it.

how far back do we need to maintain compatibility with userspace?

Is this something that we can revisit in a few years and lock it down 
then?

David Lang

> It's kind of sad to default to the world-visible thing, but as I
> mentioned in the commit, this is something where a sysadmin or distro
> can trivially just fix it at boot-time too, with just a
>
>   chmod og-r /proc/kallsyms
>
> in your bootup scripts.
>
> And if somebody has taken control of the machine _before_ the bootup
> scripts get to run, you have bigger problems than a /proc/kallsyms
> file.
>
> So I guess I'll revert it.
>
> Thanks for testing and bisecting.
>
>                      Linus
> --
> 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/
>