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

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Message-ID: <20101129233150.60a3c3af@lxorguk.ukuu.org.uk>
Date:	Mon, 29 Nov 2010 23:31:50 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Sarah Sharp <sarah.a.sharp@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Marcus Meissner <meissner@...e.de>,
	linux-kernel@...r.kernel.org, tj@...nel.org,
	akpm@...ux-foundation.org, hpa@...or.com, w@....eu
Subject: Re: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of
 attacking

> >  	/* Some debugging symbols have no name.  Ignore them. */
> > -	if (!iter->name[0])
> > +	if (!iter->name[0] || !capable(CAP_SYS_ADMIN))
> >  		return 0;

This is hardcoding file permission policy into the kernel in a way the
user cannot change - its bogus in the extreme. Use file permissions that
way saner people can chmod them as they like. Indeed quite a few people
*already* chmod chunks of /proc.

It also means that things like SELinux and Tomoyo can be used to manage
security on it in clever ways - something that using a capability
completely buggers up.

Alan
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