tracing/ftrace: fix a memory leak in stat tracing

Impact: fix memory leak

This patch fixes a memory leak inside reset_stat_list(). The freeing
loop iterated only once.

Also turn the stat_list into a simple struct list_head, which
simplify the code and avoid an unused static pointer.

Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 15 insertions, 24 deletions

diff --git a/kernel/trace/trace_stat.c b/kernel/trace/trace_stat.c
index 6f194a33a64a..4cb4ff27646d 100644
--- a/kernel/trace/trace_stat.c
+++ b/kernel/trace/trace_stat.c
@@ -21,7 +21,7 @@ struct trace_stat_list {
         void *stat;
 };
 
-static struct trace_stat_list stat_list;
+static LIST_HEAD(stat_list);
 
 /*
  * This is a copy of the current tracer to avoid racy
@@ -39,22 +39,12 @@ static DEFINE_MUTEX(stat_list_mutex);
 
 static void reset_stat_list(void)
 {
-        struct trace_stat_list *node;
-        struct list_head *next;
+        struct trace_stat_list *node, *next;
 
-        if (list_empty(&stat_list.list))
-                return;
-
-        node = list_entry(stat_list.list.next, struct trace_stat_list, list);
-        next = node->list.next;
-
-        while (&node->list != next) {
+        list_for_each_entry_safe(node, next, &stat_list, list)
                 kfree(node);
-                node = list_entry(next, struct trace_stat_list, list);
-        }
-        kfree(node);
 
-        INIT_LIST_HEAD(&stat_list.list);
+        INIT_LIST_HEAD(&stat_list);
 }
 
 void init_tracer_stat(struct tracer *trace)
@@ -107,7 +97,7 @@ static int stat_seq_init(void)
         }
 
         INIT_LIST_HEAD(&new_entry->list);
-        list_add(&new_entry->list, &stat_list.list);
+        list_add(&new_entry->list, &stat_list);
         new_entry->stat = current_tracer.stat_start();
 
         prev_stat = new_entry->stat;
@@ -130,7 +120,7 @@ static int stat_seq_init(void)
                 if (!new_entry->stat)
                         break;
 
-                list_for_each_entry(iter_entry, &stat_list.list, list) {
+                list_for_each_entry(iter_entry, &stat_list, list) {
                         /* Insertion with a descendent sorting */
                         if (current_tracer.stat_cmp(new_entry->stat,
                                                 iter_entry->stat) > 0) {
@@ -141,7 +131,7 @@ static int stat_seq_init(void)
 
                         /* The current smaller value */
                         } else if (list_is_last(&iter_entry->list,
-                                                &stat_list.list)) {
+                                                &stat_list)) {
                                 list_add(&new_entry->list, &iter_entry->list);
                                 break;
                         }
@@ -162,7 +152,7 @@ exit_free_list:
 
 static void *stat_seq_start(struct seq_file *s, loff_t *pos)
 {
-        struct trace_stat_list *l = (struct trace_stat_list *)s->private;
+        struct list_head *l = (struct list_head *)s->private;
 
         /* Prevent from tracer switch or stat_list modification */
         mutex_lock(&stat_list_mutex);
@@ -171,14 +161,14 @@ static void *stat_seq_start(struct seq_file *s, loff_t *pos)
         if (!*pos && current_tracer.stat_headers)
                 current_tracer.stat_headers(s);
 
-        return seq_list_start(&l->list, *pos);
+        return seq_list_start(l, *pos);
 }
 
 static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
 {
-        struct trace_stat_list *l = (struct trace_stat_list *)s->private;
+        struct list_head *l = (struct list_head *)s->private;
 
-        return seq_list_next(p, &l->list, pos);
+        return seq_list_next(p, l, pos);
 }
 
 static void stat_seq_stop(struct seq_file *m, void *p)
@@ -188,8 +178,10 @@ static void stat_seq_stop(struct seq_file *m, void *p)
 
 static int stat_seq_show(struct seq_file *s, void *v)
 {
-        struct trace_stat_list *l = list_entry(v, struct trace_stat_list, list);
-        return current_tracer.stat_show(s, l->stat);
+        struct trace_stat_list *entry =
+                list_entry(v, struct trace_stat_list, list);
+
+        return current_tracer.stat_show(s, entry->stat);
 }
 
 static const struct seq_operations trace_stat_seq_ops = {
@@ -237,7 +229,6 @@ static int __init tracing_stat_init(void)
         struct dentry *d_tracing;
         struct dentry *entry;
 
-        INIT_LIST_HEAD(&stat_list.list);
         d_tracing = tracing_init_dentry();
 
         entry = debugfs_create_file("trace_stat", 0444, d_tracing,