linux-kernel - /proc/kallsyms shows undefined symbols for livepatch modules

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180602173209.merjb4o5a3wsdnbh@treble>
Date:   Sat, 2 Jun 2018 12:32:33 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Jessica Yu <jeyu@...nel.org>
Cc:     linux-kernel@...r.kernel.org, live-patching@...r.kernel.org
Subject: /proc/kallsyms shows undefined symbols for livepatch modules

Hi Jessica,

I found a bug:

  [root@f25 ~]# modprobe livepatch-sample
  [root@f25 ~]# grep ' u ' /proc/kallsyms
  ffffffff81161080 u klp_enable_patch	[livepatch_sample]
  ffffffff81a01800 u __fentry__	[livepatch_sample]
  ffffffff81161250 u klp_unregister_patch	[livepatch_sample]
  ffffffff81161870 u klp_register_patch	[livepatch_sample]
  ffffffff8131f0b0 u seq_printf	[livepatch_sample]

Notice that livepatch modules' undefined symbols are showing up in
/proc/kallsyms.  This can confuse klp_find_object_symbol() which can
cause subtle bugs in livepatch.

I stared at the module kallsyms code for a bit, but I don't see the bug.
Maybe it has something to do with how we save the symbol table in
copy_module_elf().  Any ideas?

-- 
Josh