Messages in this thread | | | Date | Mon, 29 Nov 2010 11:05:58 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of attacking |
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On 11/29/2010 10:04 AM, Ingo Molnar wrote: > > * Sarah Sharp <sarah.a.sharp@linux.intel.com> wrote: > >> On Fri, Nov 26, 2010 at 08:48:09AM +0100, Ingo Molnar wrote: >>> >>> * 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. >> >> Yes, that works. The system boots as normal. `cat /proc/kallsyms` >> returns an empty file, and `sudo cat /proc/kallsyms` does not. > > Great! Marcus, mind respinning your patch with that approach? >
Can we please not use CAP_SYS_ADMIN for this? Relying on CAP_SYS_ADMIN is worse than anything else -- it is a fixed policy hardcoded in the kernel, with no ability for the system owner to delegate the policy outward, e.g. by adding group read permission and/or chgrp the file.
Delegating CAP_SYS_ADMIN, of course, otherwise known as "everything", is worse than anything...
-hpa
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