[for-linus][PATCH 2/3] tracing: Fix a memory leak by early error exit in trace_pid_write()

[Steven Rostedt]

From: Wenwen Wang <wang6495@xxxxxxx>

In trace_pid_write(), the buffer for trace parser is allocated through
kmalloc() in trace_parser_get_init(). Later on, after the buffer is used,
it is then freed through kfree() in trace_parser_put(). However, it is
possible that trace_pid_write() is terminated due to unexpected errors,
e.g., ENOMEM. In that case, the allocated buffer will not be freed, which
is a memory leak bug.

To fix this issue, free the allocated buffer when an error is encountered.

Link: http://lkml.kernel.org/r/1555726979-15633-1-git-send-email-wang6495@xxxxxxx

Fixes: f4d34a87e9c10 ("tracing: Use pid bitmap instead of a pid array for set_event_pid")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Wenwen Wang <wang6495@xxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 0cfa13a60086..46f68fad6373 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -496,8 +496,10 @@ int trace_pid_write(struct trace_pid_list *filtered_pids,
 	 * not modified.
 	 */
 	pid_list = kmalloc(sizeof(*pid_list), GFP_KERNEL);
-	if (!pid_list)
+	if (!pid_list) {
+		trace_parser_put(&parser);
 		return -ENOMEM;
+	}
 
 	pid_list->pid_max = READ_ONCE(pid_max);
 
@@ -507,6 +509,7 @@ int trace_pid_write(struct trace_pid_list *filtered_pids,
 
 	pid_list->pids = vzalloc((pid_list->pid_max + 7) >> 3);
 	if (!pid_list->pids) {
+		trace_parser_put(&parser);
 		kfree(pid_list);
 		return -ENOMEM;
 	}
-- 
2.20.1