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

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Message-ID: <AANLkTi=OsWEdrfCOHKz+SAtqo7DmK0nNxku7Ev21f0Lh@mail.gmail.com>
Date:	Fri, 19 Nov 2010 11:54:26 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Sarah Sharp <sarah.a.sharp@...ux.intel.com>
Cc:	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, 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.
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
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