[PATCH] module: Fix missing to hold module_mutex lock in module_kallsyms_lookup_name

He Kuang
2015-07-27T10:01:47Z

Function find_module_all() searches for module by name and must be
called with module_mutex. module_kallsyms_lookup_name() calls it without
this mutex which emits a warning message (CONFIG_LOCKDEP=y) by failed
assertion for testing this module_mutex lock, as following:

[ 202.877152] ------------[ cut here ]------------
[ 202.881070] WARNING: CPU: 0 PID: 1010 at kernel/module.c:281
module_assert_mutex+0x35/0x40()
[ 202.885446] Modules linked in: test_bpf
[ 202.886997] CPU: 0 PID: 1010 Comm: perf Tainted: G W 4.2.0-rc3+ #5
...

This patch wraps this call with mutex_{lock,unlock} and fix the bug.

Signed-off-by: He Kuang <hekuang@huawei.com>
---
kernel/module.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/kernel/module.c b/kernel/module.c
index 4d2b82e..43d728b 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3802,8 +3802,10 @@ unsigned long module_kallsyms_lookup_name(const char *name)
/* Don't lock: we're in enough trouble already. */
preempt_disable();
if ((colon = strchr(name, ':')) != NULL) {
+ mutex_lock(&module_mutex);
if ((mod = find_module_all(name, colon - name, false)) != NULL)
ret = mod_find_symname(mod, colon+1);
+ mutex_unlock(&module_mutex);
} else {
list_for_each_entry_rcu(mod, &modules, list) {
if (mod->state == MODULE_STATE_UNFORMED)
--
1.8.5.2