tracing/uprobes: Fix the usage of uprobe_buffer_enable() in probe_event_enable()

The usage of uprobe_buffer_enable() added by dcad1a20 is very wrong,

1. uprobe_buffer_enable() and uprobe_buffer_disable() are not balanced,
   _enable() should be called only if !enabled.

2. If uprobe_buffer_enable() fails probe_event_enable() should clear
   tp.flags and free event_file_link.

3. If uprobe_register() fails it should do uprobe_buffer_disable().

Link: http://lkml.kernel.org/p/20140627170146.GA18332@redhat.com

Acked-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Fixes: dcad1a204f72 "tracing/uprobes: Fetch args before reserving a ring buffer"
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 19 insertions, 12 deletions

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index c4cf0abd60ba..3c9b97e6b1f4 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -911,26 +911,33 @@ probe_event_enable(struct trace_uprobe *tu, struct ftrace_event_file *file,
                 tu->tp.flags |= TP_FLAG_PROFILE;
         }
 
-        ret = uprobe_buffer_enable();
-        if (ret < 0)
-                return ret;
-
         WARN_ON(!uprobe_filter_is_empty(&tu->filter));
 
         if (enabled)
                 return 0;
 
+        ret = uprobe_buffer_enable();
+        if (ret)
+                goto err_flags;
+
         tu->consumer.filter = filter;
         ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
-        if (ret) {
-                if (file) {
-                        list_del(&link->list);
-                        kfree(link);
-                        tu->tp.flags &= ~TP_FLAG_TRACE;
-                } else
-                        tu->tp.flags &= ~TP_FLAG_PROFILE;
-        }
+        if (ret)
+                goto err_buffer;
 
+        return 0;
+
+ err_buffer:
+        uprobe_buffer_disable();
+
+ err_flags:
+        if (file) {
+                list_del(&link->list);
+                kfree(link);
+                tu->tp.flags &= ~TP_FLAG_TRACE;
+        } else {
+                tu->tp.flags &= ~TP_FLAG_PROFILE;
+        }
         return ret;
 }