1 files changed, 89 insertions, 15 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index df75c06bb23f..521ad2fd1fe7 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -244,19 +244,16 @@ int trace_event_get_offsets(struct trace_event_call *call)
 	return tail->offset + tail->size;
 }
 
-/*
- * Check if the referenced field is an array and return true,
- * as arrays are OK to dereference.
- */
-static bool test_field(const char *fmt, struct trace_event_call *call)
+
+static struct trace_event_fields *find_event_field(const char *fmt,
+						   struct trace_event_call *call)
 {
 	struct trace_event_fields *field = call->class->fields_array;
-	const char *array_descriptor;
 	const char *p = fmt;
 	int len;
 
 	if (!(len = str_has_prefix(fmt, "REC->")))
-		return false;
+		return NULL;
 	fmt += len;
 	for (p = fmt; *p; p++) {
 		if (!isalnum(*p) && *p != '_')
@@ -267,11 +264,26 @@ static bool test_field(const char *fmt, struct trace_event_call *call)
 	for (; field->type; field++) {
 		if (strncmp(field->name, fmt, len) || field->name[len])
 			continue;
-		array_descriptor = strchr(field->type, '[');
-		/* This is an array and is OK to dereference. */
-		return array_descriptor != NULL;
+
+		return field;
 	}
-	return false;
+	return NULL;
+}
+
+/*
+ * Check if the referenced field is an array and return true,
+ * as arrays are OK to dereference.
+ */
+static bool test_field(const char *fmt, struct trace_event_call *call)
+{
+	struct trace_event_fields *field;
+
+	field = find_event_field(fmt, call);
+	if (!field)
+		return false;
+
+	/* This is an array and is OK to dereference. */
+	return strchr(field->type, '[') != NULL;
 }
 
 /* Look for a string within an argument */
@@ -317,6 +329,53 @@ static bool process_pointer(const char *fmt, int len, struct trace_event_call *c
 	return false;
 }
 
+/* Return true if the string is safe */
+static bool process_string(const char *fmt, int len, struct trace_event_call *call)
+{
+	const char *r, *e, *s;
+
+	e = fmt + len;
+
+	/*
+	 * There are several helper functions that return strings.
+	 * If the argument contains a function, then assume its field is valid.
+	 * It is considered that the argument has a function if it has:
+	 *   alphanumeric or '_' before a parenthesis.
+	 */
+	s = fmt;
+	do {
+		r = strstr(s, "(");
+		if (!r || r >= e)
+			break;
+		for (int i = 1; r - i >= s; i++) {
+			char ch = *(r - i);
+			if (isspace(ch))
+				continue;
+			if (isalnum(ch) || ch == '_')
+				return true;
+			/* Anything else, this isn't a function */
+			break;
+		}
+		/* A function could be wrapped in parethesis, try the next one */
+		s = r + 1;
+	} while (s < e);
+
+	/*
+	 * If there's any strings in the argument consider this arg OK as it
+	 * could be: REC->field ? "foo" : "bar" and we don't want to get into
+	 * verifying that logic here.
+	 */
+	if (find_print_string(fmt, "\"", e))
+		return true;
+
+	/* Dereferenced strings are also valid like any other pointer */
+	if (process_pointer(fmt, len, call))
+		return true;
+
+	/* Make sure the field is found, and consider it OK for now if it is */
+	return find_event_field(fmt, call) != NULL;
+}
+
 /*
  * Examine the print fmt of the event looking for unsafe dereference
  * pointers using %p* that could be recorded in the trace event and
@@ -326,6 +385,7 @@ static bool process_pointer(const char *fmt, int len, struct trace_event_call *c
 static void test_event_printk(struct trace_event_call *call)
 {
 	u64 dereference_flags = 0;
+	u64 string_flags = 0;
 	bool first = true;
 	const char *fmt;
 	int parens = 0;
@@ -416,8 +476,16 @@ static void test_event_printk(struct trace_event_call *call)
 						star = true;
 						continue;
 					}
-					if ((fmt[i + j] == 's') && star)
-						arg++;
+					if ((fmt[i + j] == 's')) {
+						if (star)
+							arg++;
+						if (WARN_ONCE(arg == 63,
+							      "Too many args for event: %s",
+							      trace_event_name(call)))
+							return;
+						dereference_flags |= 1ULL << arg;
+						string_flags |= 1ULL << arg;
+					}
 					break;
 				}
 				break;
@@ -464,7 +532,10 @@ static void test_event_printk(struct trace_event_call *call)
 			}
 
 			if (dereference_flags & (1ULL << arg)) {
-				if (process_pointer(fmt + start_arg, e - start_arg, call))
+				if (string_flags & (1ULL << arg)) {
+					if (process_string(fmt + start_arg, e - start_arg, call))
+						dereference_flags &= ~(1ULL << arg);
+				} else if (process_pointer(fmt + start_arg, e - start_arg, call))
 					dereference_flags &= ~(1ULL << arg);
 			}
 
@@ -476,7 +547,10 @@ static void test_event_printk(struct trace_event_call *call)
 	}
 
 	if (dereference_flags & (1ULL << arg)) {
-		if (process_pointer(fmt + start_arg, i - start_arg, call))
+		if (string_flags & (1ULL << arg)) {
+			if (process_string(fmt + start_arg, i - start_arg, call))
+				dereference_flags &= ~(1ULL << arg);
+		} else if (process_pointer(fmt + start_arg, i - start_arg, call))
 			dereference_flags &= ~(1ULL << arg);
 	}