tracing/probes: cleanup: Set trace_probe::nr_args at trace_probe_init

[ Upstream commit 035ba76014c096316fa809a46ce0a1b9af1cde0d ]

Instead of incrementing the trace_probe::nr_args, init it at
trace_probe_init(). Without this change, there is no way to get the number
of trace_probe arguments while parsing it.
This is a cleanup, so the behavior is not changed.

Link: https://lore.kernel.org/all/170952363585.229804.13060759900346411951.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Stable-dep-of: 373b9338c972 ("uprobe: avoid out-of-bounds memory access of fetching args")
Signed-off-by: Sasha Levin <sashal@kernel.org>

kernel/trace/trace_eprobe.c

@@ -220,7 +220,7 @@ static struct trace_eprobe *alloc_event_probe(const char *group,
 	if (!ep->event_system)
 		goto error;
 
-	ret = trace_probe_init(&ep->tp, this_event, group, false);
+	ret = trace_probe_init(&ep->tp, this_event, group, false, nargs);
 	if (ret < 0)
 		goto error;
 

kernel/trace/trace_fprobe.c

@@ -389,7 +389,7 @@ static struct trace_fprobe *alloc_trace_fprobe(const char *group,
 	tf->tpoint = tpoint;
 	tf->fp.nr_maxactive = maxactive;
 
-	ret = trace_probe_init(&tf->tp, event, group, false);
+	ret = trace_probe_init(&tf->tp, event, group, false, nargs);
 	if (ret < 0)
 		goto error;
 

kernel/trace/trace_kprobe.c

@@ -290,7 +290,7 @@ static struct trace_kprobe *alloc_trace_kprobe(const char *group,
 	INIT_HLIST_NODE(&tk->rp.kp.hlist);
 	INIT_LIST_HEAD(&tk->rp.kp.list);
 
-	ret = trace_probe_init(&tk->tp, event, group, false);
+	ret = trace_probe_init(&tk->tp, event, group, false, nargs);
 	if (ret < 0)
 		goto error;
 

kernel/trace/trace_probe.c

@@ -1383,9 +1383,6 @@ int traceprobe_parse_probe_arg(struct trace_probe *tp, int i, const char *arg,
 	struct probe_arg *parg = &tp->args[i];
 	const char *body;
 
-	/* Increment count for freeing args in error case */
-	tp->nr_args++;
-
 	body = strchr(arg, '=');
 	if (body) {
 		if (body - arg > MAX_ARG_NAME_LEN) {
@@ -1770,7 +1767,7 @@ void trace_probe_cleanup(struct trace_probe *tp)
 }
 
 int trace_probe_init(struct trace_probe *tp, const char *event,
-		     const char *group, bool alloc_filter)
+		     const char *group, bool alloc_filter, int nargs)
 {
 	struct trace_event_call *call;
 	size_t size = sizeof(struct trace_probe_event);
@@ -1806,6 +1803,11 @@ int trace_probe_init(struct trace_probe *tp, const char *event,
 		goto error;
 	}
 
+	tp->nr_args = nargs;
+	/* Make sure pointers in args[] are NULL */
+	if (nargs)
+		memset(tp->args, 0, sizeof(tp->args[0]) * nargs);
+
 	return 0;
 
 error:

kernel/trace/trace_probe.h

@@ -338,7 +338,7 @@ static inline bool trace_probe_has_single_file(struct trace_probe *tp)
 }
 
 int trace_probe_init(struct trace_probe *tp, const char *event,
-		     const char *group, bool alloc_filter);
+		     const char *group, bool alloc_filter, int nargs);
 void trace_probe_cleanup(struct trace_probe *tp);
 int trace_probe_append(struct trace_probe *tp, struct trace_probe *to);
 void trace_probe_unlink(struct trace_probe *tp);

kernel/trace/trace_uprobe.c

@@ -337,7 +337,7 @@ alloc_trace_uprobe(const char *group, const char *event, int nargs, bool is_ret)
 	if (!tu)
 		return ERR_PTR(-ENOMEM);
 
-	ret = trace_probe_init(&tu->tp, event, group, true);
+	ret = trace_probe_init(&tu->tp, event, group, true, nargs);
 	if (ret < 0)
 		goto error;