1 files changed, 176 insertions, 49 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 77e68efbd43e..1545cc8b49d0 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -82,7 +82,7 @@ static int system_refcount_dec(struct event_subsystem *system)
 	}
 
 static struct ftrace_event_field *
-__find_event_field(struct list_head *head, char *name)
+__find_event_field(struct list_head *head, const char *name)
 {
 	struct ftrace_event_field *field;
 
@@ -114,7 +114,8 @@ trace_find_event_field(struct trace_event_call *call, char *name)
 
 static int __trace_define_field(struct list_head *head, const char *type,
 				const char *name, int offset, int size,
-				int is_signed, int filter_type, int len)
+				int is_signed, int filter_type, int len,
+				int need_test)
 {
 	struct ftrace_event_field *field;
 
@@ -133,6 +134,7 @@ static int __trace_define_field(struct list_head *head, const char *type,
 	field->offset = offset;
 	field->size = size;
 	field->is_signed = is_signed;
+	field->needs_test = need_test;
 	field->len = len;
 
 	list_add(&field->link, head);
@@ -151,13 +153,13 @@ int trace_define_field(struct trace_event_call *call, const char *type,
 
 	head = trace_get_fields(call);
 	return __trace_define_field(head, type, name, offset, size,
-				    is_signed, filter_type, 0);
+				    is_signed, filter_type, 0, 0);
 }
 EXPORT_SYMBOL_GPL(trace_define_field);
 
 static int trace_define_field_ext(struct trace_event_call *call, const char *type,
 		       const char *name, int offset, int size, int is_signed,
-		       int filter_type, int len)
+		       int filter_type, int len, int need_test)
 {
 	struct list_head *head;
 
@@ -166,13 +168,13 @@ static int trace_define_field_ext(struct trace_event_call *call, const char *typ
 
 	head = trace_get_fields(call);
 	return __trace_define_field(head, type, name, offset, size,
-				    is_signed, filter_type, len);
+				    is_signed, filter_type, len, need_test);
 }
 
 #define __generic_field(type, item, filter_type)			\
 	ret = __trace_define_field(&ftrace_generic_fields, #type,	\
 				   #item, 0, 0, is_signed_type(type),	\
-				   filter_type, 0);			\
+				   filter_type, 0, 0);			\
 	if (ret)							\
 		return ret;
 
@@ -181,7 +183,8 @@ static int trace_define_field_ext(struct trace_event_call *call, const char *typ
 				   "common_" #item,			\
 				   offsetof(typeof(ent), item),		\
 				   sizeof(ent.item),			\
-				   is_signed_type(type), FILTER_OTHER, 0);	\
+				   is_signed_type(type), FILTER_OTHER,	\
+				   0, 0);				\
 	if (ret)							\
 		return ret;
 
@@ -244,19 +247,16 @@ 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 != '_')
@@ -265,16 +265,129 @@ static bool test_field(const char *fmt, struct trace_event_call *call)
 	len = p - fmt;
 
 	for (; field->type; field++) {
-		if (strncmp(field->name, fmt, len) ||
-		    field->name[len])
+		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 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 */
+static bool find_print_string(const char *arg, const char *str, const char *end)
+{
+	const char *r;
+
+	r = strstr(arg, str);
+	return r && r < end;
+}
+
+/* Return true if the argument pointer is safe */
+static bool process_pointer(const char *fmt, int len, struct trace_event_call *call)
+{
+	const char *r, *e, *a;
+
+	e = fmt + len;
+
+	/* Find the REC-> in the argument */
+	r = strstr(fmt, "REC->");
+	if (r && r < e) {
+		/*
+		 * Addresses of events on the buffer, or an array on the buffer is
+		 * OK to dereference. There's ways to fool this, but
+		 * this is to catch common mistakes, not malicious code.
+		 */
+		a = strchr(fmt, '&');
+		if ((a && (a < r)) || test_field(r, call))
+			return true;
+	} else if (find_print_string(fmt, "__get_dynamic_array(", e)) {
+		return true;
+	} else if (find_print_string(fmt, "__get_rel_dynamic_array(", e)) {
+		return true;
+	} else if (find_print_string(fmt, "__get_dynamic_array_len(", e)) {
+		return true;
+	} else if (find_print_string(fmt, "__get_rel_dynamic_array_len(", e)) {
+		return true;
+	} else if (find_print_string(fmt, "__get_sockaddr(", e)) {
+		return true;
+	} else if (find_print_string(fmt, "__get_rel_sockaddr(", e)) {
+		return true;
 	}
 	return false;
 }
 
+/* Return true if the string is safe */
+static bool process_string(const char *fmt, int len, struct trace_event_call *call)
+{
+	struct trace_event_fields *field;
+	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 */
+	field = find_event_field(fmt, call);
+	if (!field)
+		return false;
+
+	/* Test this field's string before printing the event */
+	call->flags |= TRACE_EVENT_FL_TEST_STR;
+	field->needs_test = 1;
+
+	return true;
+}
+
 /*
  * Examine the print fmt of the event looking for unsafe dereference
  * pointers using %p* that could be recorded in the trace event and
@@ -284,13 +397,14 @@ static bool test_field(const char *fmt, struct trace_event_call *call)
 static void test_event_printk(struct trace_event_call *call)
 {
 	u64 dereference_flags = 0;
+	u64 string_flags = 0;
 	bool first = true;
-	const char *fmt, *c, *r, *a;
+	const char *fmt;
 	int parens = 0;
 	char in_quote = 0;
 	int start_arg = 0;
 	int arg = 0;
-	int i;
+	int i, e;
 
 	fmt = call->print_fmt;
 
@@ -374,8 +488,16 @@ 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;
@@ -403,42 +525,47 @@ static void test_event_printk(struct trace_event_call *call)
 		case ',':
 			if (in_quote || parens)
 				continue;
+			e = i;
 			i++;
 			while (isspace(fmt[i]))
 				i++;
-			start_arg = i;
-			if (!(dereference_flags & (1ULL << arg)))
-				goto next_arg;
 
-			/* Find the REC-> in the argument */
-			c = strchr(fmt + i, ',');
-			r = strstr(fmt + i, "REC->");
-			if (r && (!c || r < c)) {
-				/*
-				 * Addresses of events on the buffer,
-				 * or an array on the buffer is
-				 * OK to dereference.
-				 * There's ways to fool this, but
-				 * this is to catch common mistakes,
-				 * not malicious code.
-				 */
-				a = strchr(fmt + i, '&');
-				if ((a && (a < r)) || test_field(r, call))
+			/*
+			 * If start_arg is zero, then this is the start of the
+			 * first argument. The processing of the argument happens
+			 * when the end of the argument is found, as it needs to
+			 * handle paranthesis and such.
+			 */
+			if (!start_arg) {
+				start_arg = i;
+				/* Balance out the i++ in the for loop */
+				i--;
+				continue;
+			}
+
+			if (dereference_flags & (1ULL << arg)) {
+				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);
-			} else if ((r = strstr(fmt + i, "__get_dynamic_array(")) &&
-				   (!c || r < c)) {
-				dereference_flags &= ~(1ULL << arg);
-			} else if ((r = strstr(fmt + i, "__get_sockaddr(")) &&
-				   (!c || r < c)) {
-				dereference_flags &= ~(1ULL << arg);
 			}
 
-		next_arg:
-			i--;
+			start_arg = i;
 			arg++;
+			/* Balance out the i++ in the for loop */
+			i--;
 		}
 	}
 
+	if (dereference_flags & (1ULL << arg)) {
+		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);
+	}
+
 	/*
 	 * If you triggered the below warning, the trace event reported
 	 * uses an unsafe dereference pointer %p*. As the data stored
@@ -2471,7 +2598,7 @@ event_define_fields(struct trace_event_call *call)
 			ret = trace_define_field_ext(call, field->type, field->name,
 						 offset, field->size,
 						 field->is_signed, field->filter_type,
-						 field->len);
+						 field->len, field->needs_test);
 			if (WARN_ON_ONCE(ret)) {
 				pr_err("error code is %d\n", ret);
 				break;