[PATCH] module: annotate failed-module stats list traversal

[Runyu Xiao]

read_file_mod_stats() dumps dup_failed_modules while holding
module_mutex, but the loop uses list_for_each_entry_rcu() without
telling lockdep about that non-RCU protection.

The same list is already traversed in try_add_failed_module() with
lockdep_is_held(&module_mutex) as the RCU-list lockdep condition. Use
the same condition for the debugfs stats dump so CONFIG_PROVE_RCU_LIST
can see the documented protection.

This was found by our static analysis tool and then manually reviewed
against the current tree. The dynamic triage evidence is a
target-matched CONFIG_PROVE_RCU_LIST warning; the change is limited
to documenting the existing protection contract.

This is a lockdep annotation cleanup. It does not change the list
lifetime or serialization rules.

Signed-off-by: Runyu Xiao <runyu.xiao@xxxxxxxxxx>
---
 kernel/module/stats.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/module/stats.c b/kernel/module/stats.c
index 3ba0e98b3c91..79c227a72a21 100644
--- a/kernel/module/stats.c
+++ b/kernel/module/stats.c
@@ -382,7 +382,8 @@ static ssize_t read_file_mod_stats(struct file *file, char __user *user_buf,
 	mutex_lock(&module_mutex);
 
 
-	list_for_each_entry_rcu(mod_fail, &dup_failed_modules, list) {
+	list_for_each_entry_rcu(mod_fail, &dup_failed_modules, list,
+				lockdep_is_held(&module_mutex)) {
 		if (WARN_ON_ONCE(++count_failed >= MAX_FAILED_MOD_PRINT))
 			goto out_unlock;
 		len += scnprintf(buf + len, size - len, "%25s\t%15lu\t%25s\n", mod_fail->name,
-- 
2.34.1