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

* Linus Torvalds <> wrote:

> On Fri, Nov 19, 2010 at 11:19 AM, Sarah Sharp
> <> 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.


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


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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