From 179ad61c39b5164f2b9f48f355fc1ad3ec73c8a4 Mon Sep 17 00:00:00 2001
From: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Date: Tue, 18 Jan 2022 09:46:48 -0500
Subject: [PATCH] Backport: lttng_buffer_view_is_valid,
 lttng_buffer_view_contains_string
MIME-Version: 1.0
Content-Type: text/plain; charset=utf8
Content-Transfer-Encoding: 8bit

Change-Id: I23892e6f20e2847037ba16ad1bba8b2d5a9e0a7c
Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---
 src/common/buffer-view.c | 48 ++++++++++++++++++++++++++++++++++++++++
 src/common/buffer-view.h | 25 +++++++++++++++++++++
 2 files changed, 73 insertions(+)

diff --git a/src/common/buffer-view.c b/src/common/buffer-view.c
index 4bdb1eb7d..7337dbb06 100644
--- a/src/common/buffer-view.c
+++ b/src/common/buffer-view.c
@@ -18,6 +18,12 @@ struct lttng_buffer_view lttng_buffer_view_init(
 	return view;
 }
 
+LTTNG_HIDDEN
+bool lttng_buffer_view_is_valid(const struct lttng_buffer_view *view)
+{
+	return view && view->data && view->size > 0;
+}
+
 LTTNG_HIDDEN
 struct lttng_buffer_view lttng_buffer_view_from_view(
 		const struct lttng_buffer_view *src, size_t offset,
@@ -67,3 +73,45 @@ struct lttng_buffer_view lttng_buffer_view_from_dynamic_buffer(
 end:
 	return view;
 }
+
+LTTNG_HIDDEN
+bool lttng_buffer_view_contains_string(const struct lttng_buffer_view *buf,
+		const char *str,
+		size_t len_with_null_terminator)
+{
+	const char *past_buf_end;
+	size_t max_str_len_with_null_terminator;
+	size_t str_len;
+	bool ret;
+
+	past_buf_end = buf->data + buf->size;
+
+	/* Is the start of the string in the buffer view? */
+	if (str < buf->data || str >= past_buf_end) {
+		ret = false;
+		goto end;
+	}
+
+	/*
+	 * Max length the string could have to fit in the buffer, including
+	 * NULL terminator.
+	 */
+	max_str_len_with_null_terminator = past_buf_end - str;
+
+	/* Could the string even fit in the buffer? */
+	if (len_with_null_terminator > max_str_len_with_null_terminator) {
+		ret = false;
+		goto end;
+	}
+
+	str_len = lttng_strnlen(str, max_str_len_with_null_terminator);
+	if (str_len != (len_with_null_terminator - 1)) {
+		ret = false;
+		goto end;
+	}
+
+	ret = true;
+
+end:
+	return ret;
+}
diff --git a/src/common/buffer-view.h b/src/common/buffer-view.h
index e8c351b3f..c430a68ec 100644
--- a/src/common/buffer-view.h
+++ b/src/common/buffer-view.h
@@ -11,6 +11,7 @@
 #include <stddef.h>
 #include <stdint.h>
 #include <common/macros.h>
+#include <stdbool.h>
 
 struct lttng_dynamic_buffer;
 
@@ -34,6 +35,17 @@ LTTNG_HIDDEN
 struct lttng_buffer_view lttng_buffer_view_init(
 		const char *src, size_t offset, ptrdiff_t len);
 
+/**
+ * Checks if a buffer view is safe to access.
+ *
+ * After calling the buffer view creation functions, callers should verify
+ * if the resquested length (if any is explicitly provided) could be mapped
+ * to a new view.
+ *
+ * @view	Buffer view to validate
+ */
+bool lttng_buffer_view_is_valid(const struct lttng_buffer_view *view);
+
 /**
  * Return a buffer view referencing a subset of the memory referenced by another
  * view.
@@ -70,4 +82,17 @@ struct lttng_buffer_view lttng_buffer_view_from_dynamic_buffer(
 		const struct lttng_dynamic_buffer *src, size_t offset,
 		ptrdiff_t len);
 
+/**
+ * Verify that `buf` contains a string starting at `str` of length
+ * `len_with_null_terminator`.
+ *
+ * @buf				The buffer view
+ * @str				The start of the string
+ * @len_with_null_terminator	Expected length of the string, including the
+ * 				NULL terminator.
+ */
+bool lttng_buffer_view_contains_string(const struct lttng_buffer_view *buf,
+		const char *str,
+		size_t len_with_null_terminator);
+
 #endif /* LTTNG_BUFFER_VIEW_H */
-- 
2.34.1