linux-kernel - [PATCH] module: Fix missing to hold module_mutex lock in module_kallsyms_lookup

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Date:	Mon, 27 Jul 2015 10:01:26 +0000
From:	He Kuang <hekuang@...wei.com>
To:	<rusty@...tcorp.com.au>
CC:	<wangnan0@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] module: Fix missing to hold module_mutex lock in module_kallsyms_lookup_name

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@...wei.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

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