tracing: Fix a memory leak by early error exit in trace_pid_write()

BugLink: https://bugs.launchpad.net/bugs/1838459
commit 91862cc7867bba4ee5c8fcf0ca2f1d30427b6129 upstream.

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@umn.edu
Fixes: f4d34a87e9c10 ("tracing: Use pid bitmap instead of a pid array for set_event_pid")
Cc: stable@vger.kernel.org
Signed-off-by: Wenwen Wang <wang6495@umn.edu>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f401cc38706188c9c3016b8b86d624d3b01a72a3..e94b7478fec1fb990618a8ecf5a1f9c0addd6e29 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -494,8 +494,10 @@ 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);
 
@@ -505,6 +507,7 @@ 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;
        }