[PATCH 3.16 295/366] tracing/kprobes: Fix trace_probe flags on enable_trace_kprobe() failure

[Ben Hutchings]

3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Artem Savkov <asavkov@xxxxxxxxxx>

commit 57ea2a34adf40f3a6e88409aafcf803b8945619a upstream.

If enable_trace_kprobe fails to enable the probe in enable_k(ret)probe
it returns an error, but does not unset the tp flags it set previously.
This results in a probe being considered enabled and failures like being
unable to remove the probe through kprobe_events file since probes_open()
expects every probe to be disabled.

Link: http://lkml.kernel.org/r/20180725102826.8300-1-asavkov@xxxxxxxxxx
Link: http://lkml.kernel.org/r/20180725142038.4765-1-asavkov@xxxxxxxxxx

Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Fixes: 41a7dd420c57 ("tracing/kprobes: Support ftrace_event_file base multibuffer")
Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Artem Savkov <asavkov@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 kernel/trace/trace_kprobe.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -361,11 +361,10 @@ static struct trace_kprobe *find_trace_k
 static int
 enable_trace_kprobe(struct trace_kprobe *tk, struct ftrace_event_file *file)
 {
+	struct event_file_link *link;
 	int ret = 0;
 
 	if (file) {
-		struct event_file_link *link;
-
 		link = kmalloc(sizeof(*link), GFP_KERNEL);
 		if (!link) {
 			ret = -ENOMEM;
@@ -385,6 +384,16 @@ enable_trace_kprobe(struct trace_kprobe
 		else
 			ret = enable_kprobe(&tk->rp.kp);
 	}
+
+	if (ret) {
+		if (file) {
+			list_del_rcu(&link->list);
+			kfree(link);
+			tk->tp.flags &= ~TP_FLAG_TRACE;
+		} else {
+			tk->tp.flags &= ~TP_FLAG_PROFILE;
+		}
+	}
  out:
 	return ret;
 }