kprobes: fix trace_probe flags in enable_trace_kprobe

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 previosly. 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.

Signed-off-by Artem Savkov <[email protected]>

---
 kernel/trace/trace_kprobe.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

kernel/trace/trace_kprobe.c +11 -2

index 21f718472942..fb887ced5056 100644
@@ -400,11 +400,10 @@ static struct trace_kprobe *find_trace_kprobe(const char *event,
 static int
 enable_trace_kprobe(struct trace_kprobe *tk, struct trace_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;

@@ -424,6 +423,16 @@ enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
 		else
 			ret = enable_kprobe(&tk->rp.kp);
 	}
+
+	if (ret) {
+		if (file) {
+			list_del(&link->list);
+			kfree(link);
+			tk->tp.flags &= ~TP_FLAG_TRACE;
+		} else {
+			tk->tp.flags &= ~TP_FLAG_PROFILE;
+		}
+	}
  out:
 	return ret;
 }

[ Adding Masami to Cc ]

On Wed, 25 Jul 2018 12:28:26 +0200
Artem Savkov <[email protected]> wrote:

Quoted 6 lines

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 previosly. 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.

Looks good to me. Masami, want to ack it?

-- Steve

Quoted 39 lines

Signed-off-by Artem Savkov <[email protected]>

---
 kernel/trace/trace_kprobe.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

kernel/trace/trace_kprobe.c +11 -2

index 21f718472942..fb887ced5056 100644
@@ -400,11 +400,10 @@ static struct trace_kprobe *find_trace_kprobe(const char *event,
 static int
 enable_trace_kprobe(struct trace_kprobe *tk, struct trace_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;

@@ -424,6 +423,16 @@ enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
 		else
 			ret = enable_kprobe(&tk->rp.kp);
 	}
+
+	if (ret) {
+		if (file) {
+			list_del(&link->list);
+			kfree(link);
+			tk->tp.flags &= ~TP_FLAG_TRACE;
+		} else {
+			tk->tp.flags &= ~TP_FLAG_PROFILE;
+		}
+	}
  out:
 	return ret;
 }

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 previosly.

Quoted 2 lines · Artem Savkov

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 previosly.

"previously"

kernel/trace/trace_kprobe.c enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file) · line 429

Quoted 9 lines

kernel/trace/trace_kprobe.c +4 -0

@@ -424,6 +423,16 @@ enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
 		else
 			ret = enable_kprobe(&tk->rp.kp);
 	}
+
+	if (ret) {
+		if (file) {
+			list_del(&link->list);  

Should this be list_del_rcu(), since it was added to the list with list_add_tail_rcu()?