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authorKees Cook <keescook@chromium.org>2014-03-10 13:42:48 -0700
committerH. Peter Anvin <hpa@linux.intel.com>2014-03-24 10:18:26 -0700
commit9dd721c6dbfc310f94306902611f86dda87a45fa (patch)
tree56dbfcb8ae3c05f26be75dba824c5fb18b1ac25f /arch/x86
parente2b32e6785138d92d2a40e0d0473575c8c7310a2 (diff)
downloadlinux-9dd721c6dbfc310f94306902611f86dda87a45fa.tar.bz2
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>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kernel/module.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index 49483137371f..e69f9882bf95 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -48,6 +48,9 @@ do { \
static unsigned long module_load_offset;
static int randomize_modules = 1;
+/* Mutex protects the module_load_offset. */
+static DEFINE_MUTEX(module_kaslr_mutex);
+
static int __init parse_nokaslr(char *p)
{
randomize_modules = 0;
@@ -58,7 +61,7 @@ early_param("nokaslr", parse_nokaslr);
static unsigned long int get_module_load_offset(void)
{
if (randomize_modules) {
- mutex_lock(&module_mutex);
+ mutex_lock(&module_kaslr_mutex);
/*
* Calculate the module_load_offset the first time this
* code is called. Once calculated it stays the same until
@@ -67,7 +70,7 @@ static unsigned long int get_module_load_offset(void)
if (module_load_offset == 0)
module_load_offset =
(get_random_int() % 1024 + 1) * PAGE_SIZE;
- mutex_unlock(&module_mutex);
+ mutex_unlock(&module_kaslr_mutex);
}
return module_load_offset;
}