tracing/filters: NIL-terminate user input filter

Make sure messages from user space are NIL-terminated strings,
otherwise we could dump random memory while reading filter file.

Try this:
 # echo 'parent_comm ==' > events/sched/sched_process_fork/filter
 # cat events/sched/sched_process_fork/filter
 parent_comm == �

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Tom Zanussi <tzanussi@gmail.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <49E04C32.6060508@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 64ec4d278ffb..054bc1802bcd 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -503,6 +503,7 @@ event_filter_write(struct file *filp, const char __user *ubuf, size_t cnt,
 
         if (copy_from_user(&buf, ubuf, cnt))
                 return -EFAULT;
+        buf[cnt] = '\0';
 
         pred = kzalloc(sizeof(*pred), GFP_KERNEL);
         if (!pred)
@@ -569,6 +570,7 @@ subsystem_filter_write(struct file *filp, const char __user *ubuf, size_t cnt,
 
         if (copy_from_user(&buf, ubuf, cnt))
                 return -EFAULT;
+        buf[cnt] = '\0';
 
         pred = kzalloc(sizeof(*pred), GFP_KERNEL);
         if (!pred)