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

[Ingo Molnar <mingo@elte.hu>]

* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Fri, Nov 19, 2010 at 11:19 AM, Sarah Sharp
> <sarah.a.sharp@linux.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]) {