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

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Message-ID: <20101126074809.GD19589@elte.hu>
Date:	Fri, 26 Nov 2010 08:48:09 +0100
From:	Ingo Molnar <mingo@...e.hu>
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, w@....eu,
	alan@...rguk.ukuu.org.uk
Subject: Re: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of
 attacking


* Linus Torvalds <torvalds@...ux-foundation.org> 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.

Sarah,

Does your system boot fine if we make /proc/kallsyms simply an empty file to 
unprivileged users? Something like the (untested ...) patch below.

	Ingo

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 6f6d091..d54c993 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -465,7 +465,7 @@ static int s_show(struct seq_file *m, void *p)
 	struct kallsym_iter *iter = m->private;
 
 	/* Some debugging symbols have no name.  Ignore them. */
-	if (!iter->name[0])
+	if (!iter->name[0] || !capable(CAP_SYS_ADMIN))
 		return 0;
 
 	if (iter->module_name[0]) {
--
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