tracing: fix memory leak in trace_stat
If the function profiler does not have any items recorded and one were
to cat the function stat file, the kernel would take a BUG with a NULL
pointer dereference.
Looking further into this, I found that returning NULL from stat_start
did not stop the stat logic, and would later call stat_next. This breaks
from the way seq_file works, so I looked into fixing the stat code.
This is where I noticed that the last next_entry is never freed.
It is allocated, and if the stat_next returns NULL, the code breaks out
of the loop, unlocks the mutex and exits. We never link the next_entry
nor do we free it. Thus it is a real memory leak.
This patch rearranges the code a bit to not only fix the memory leak,
but also to act more like seq_file where nothing is printed if there
is nothing to print. That is, stat_start returns NULL.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
diff --git a/kernel/trace/trace_stat.c b/kernel/trace/trace_stat.c
index 39310e3..f71b85b 100644
--- a/kernel/trace/trace_stat.c
+++ b/kernel/trace/trace_stat.c
@@ -75,7 +75,7 @@
{
struct trace_stat_list *iter_entry, *new_entry;
struct tracer_stat *ts = session->ts;
- void *prev_stat;
+ void *stat;
int ret = 0;
int i;
@@ -85,6 +85,10 @@
if (!ts->stat_cmp)
ts->stat_cmp = dummy_cmp;
+ stat = ts->stat_start();
+ if (!stat)
+ goto exit;
+
/*
* The first entry. Actually this is the second, but the first
* one (the stat_list head) is pointless.
@@ -99,14 +103,19 @@
list_add(&new_entry->list, &session->stat_list);
- new_entry->stat = ts->stat_start();
- prev_stat = new_entry->stat;
+ new_entry->stat = stat;
/*
* Iterate over the tracer stat entries and store them in a sorted
* list.
*/
for (i = 1; ; i++) {
+ stat = ts->stat_next(stat, i);
+
+ /* End of insertion */
+ if (!stat)
+ break;
+
new_entry = kmalloc(sizeof(struct trace_stat_list), GFP_KERNEL);
if (!new_entry) {
ret = -ENOMEM;
@@ -114,11 +123,7 @@
}
INIT_LIST_HEAD(&new_entry->list);
- new_entry->stat = ts->stat_next(prev_stat, i);
-
- /* End of insertion */
- if (!new_entry->stat)
- break;
+ new_entry->stat = stat;
list_for_each_entry(iter_entry, &session->stat_list, list) {
@@ -137,8 +142,6 @@
break;
}
}
-
- prev_stat = new_entry->stat;
}
exit:
mutex_unlock(&session->stat_mutex);