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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>
This commit is contained in:
Steven Rostedt 2009-03-21 02:44:50 -04:00
parent 45b9560895
commit 098335215a
1 changed files with 13 additions and 10 deletions
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23
kernel/trace/trace_stat.c
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@ -75,7 +75,7 @@ static int stat_seq_init(struct tracer_stat_session *session)
{
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 @@ static int stat_seq_init(struct tracer_stat_session *session)
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 @@ static int stat_seq_init(struct tracer_stat_session *session)
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 @@ static int stat_seq_init(struct tracer_stat_session *session)
}
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 @@ static int stat_seq_init(struct tracer_stat_session *session)
break;
}
}
prev_stat = new_entry->stat;
}
exit:
mutex_unlock(&session->stat_mutex);