Merge tag 'trace-v5.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fix from Steven Rostedt:
 "Fix synthetic event "strcat" overrun

  New synthetic event code used strcat() and miscalculated the ending,
  causing the concatenation to write beyond the allocated memory.

  Instead of using strncat(), the code is switched over to seq_buf which
  has all the mechanisms in place to protect against writing more than
  what is allocated, and cleans up the code a bit"

* tag 'trace-v5.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing, synthetic events: Replace buggy strcat() with seq_buf operations

1 files changed, 22 insertions, 14 deletions

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index 3212e2c653b3..84b7cab55291 100644
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -585,6 +585,7 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
 	struct synth_field *field;
 	const char *prefix = NULL, *field_type = argv[0], *field_name, *array;
 	int len, ret = 0;
+	struct seq_buf s;
 	ssize_t size;
 
 	if (field_type[0] == ';')
@@ -630,13 +631,9 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
 		field_type++;
 	len = strlen(field_type) + 1;
 
-        if (array) {
-                int l = strlen(array);
+	if (array)
+		len += strlen(array);
 
-                if (l && array[l - 1] == ';')
-                        l--;
-                len += l;
-        }
 	if (prefix)
 		len += strlen(prefix);
 
@@ -645,14 +642,18 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
 		ret = -ENOMEM;
 		goto free;
 	}
+	seq_buf_init(&s, field->type, len);
 	if (prefix)
-		strcat(field->type, prefix);
-	strcat(field->type, field_type);
+		seq_buf_puts(&s, prefix);
+	seq_buf_puts(&s, field_type);
 	if (array) {
-		strcat(field->type, array);
-		if (field->type[len - 1] == ';')
-			field->type[len - 1] = '\0';
+		seq_buf_puts(&s, array);
+		if (s.buffer[s.len - 1] == ';')
+			s.len--;
 	}
+	if (WARN_ON_ONCE(!seq_buf_buffer_left(&s)))
+		goto free;
+	s.buffer[s.len] = '\0';
 
 	size = synth_field_size(field->type);
 	if (size < 0) {
@@ -663,14 +664,21 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
 		if (synth_field_is_string(field->type)) {
 			char *type;
 
-			type = kzalloc(sizeof("__data_loc ") + strlen(field->type) + 1, GFP_KERNEL);
+			len = sizeof("__data_loc ") + strlen(field->type) + 1;
+			type = kzalloc(len, GFP_KERNEL);
 			if (!type) {
 				ret = -ENOMEM;
 				goto free;
 			}
 
-			strcat(type, "__data_loc ");
-			strcat(type, field->type);
+			seq_buf_init(&s, type, len);
+			seq_buf_puts(&s, "__data_loc ");
+			seq_buf_puts(&s, field->type);
+
+			if (WARN_ON_ONCE(!seq_buf_buffer_left(&s)))
+				goto free;
+			s.buffer[s.len] = '\0';
+
 			kfree(field->type);
 			field->type = type;