From: Kees Cook <keescook@chromium.org>
Date: Mon, 10 Mar 2014 20:42:48 +0000 (-0700)
Subject: x86, kaslr: fix module lock ordering problem
X-Git-Tag: v3.15-rc1~170^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9dd721c6dbfc310f94306902611f86dda87a45fa;p=pandora-kernel.git

x86, kaslr: fix module lock ordering problem

There was a potential lock ordering problem with the module kASLR patch
("x86, kaslr: randomize module base load address"). This patch removes
the usage of the module_mutex and creates a new mutex to protect the
module base address offset value.

Chain exists of:
  text_mutex --> kprobe_insn_slots.mutex --> module_mutex

[    0.515561]  Possible unsafe locking scenario:
[    0.515561]
[    0.515561]        CPU0                    CPU1
[    0.515561]        ----                    ----
[    0.515561]   lock(module_mutex);
[    0.515561]                                lock(kprobe_insn_slots.mutex);
[    0.515561]                                lock(module_mutex);
[    0.515561]   lock(text_mutex);
[    0.515561]
[    0.515561]  *** DEADLOCK ***

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Andy Honig <ahonig@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---

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