[RFC, WIP, v4 06/11] media: vidtv: add wrappers for memcpy and memset

["Daniel W. S. Almeida" <dwlsalmeida@gmail.com>]

From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

A lot of code in this driver is for serializing structures. This is
error prone.

Therefore, prevent buffer overflows by wrapping memcpy and memset,
comparing the requested length against the buffer size.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
---
 drivers/media/test-drivers/vidtv/Makefile     |  3 ++
 .../media/test-drivers/vidtv/vidtv_common.c   | 44 +++++++++++++++++++
 .../media/test-drivers/vidtv/vidtv_common.h   | 28 ++++++++++++
 3 files changed, 75 insertions(+)
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_common.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_common.h

diff --git a/drivers/media/test-drivers/vidtv/Makefile b/drivers/media/test-drivers/vidtv/Makefile
index a9f1993dd5443..9ea9485d42189 100644
--- a/drivers/media/test-drivers/vidtv/Makefile
+++ b/drivers/media/test-drivers/vidtv/Makefile
@@ -1,3 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 
+vidtv_demod-objs := vidtv_common.o
+vidtv_bridge-objs := vidtv_common.o
+
 obj-$(CONFIG_DVB_VIDTV)	+= vidtv_tuner.o vidtv_demod.o vidtv_bridge.o
diff --git a/drivers/media/test-drivers/vidtv/vidtv_common.c b/drivers/media/test-drivers/vidtv/vidtv_common.c
new file mode 100644
index 0000000000000..28f10630499a9
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_common.c
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * The Virtual DVB test driver serves as a reference DVB driver and helps
+ * validate the existing APIs in the media subsystem. It can also aid
+ * developers working on userspace applications.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/printk.h>
+
+u32 vidtv_memcpy(void *to,
+		 const void *from,
+		 size_t len,
+		 u32 offset,
+		 u32 buf_sz)
+{
+	if (buf_sz && offset + len > buf_sz) {
+		pr_err("%s: overflow detected, skipping. Try increasing the buffer size",
+		       __func__);
+		return 0;
+	}
+
+	memcpy(to, from, len);
+	return len;
+}
+
+u32 vidtv_memset(void *to,
+		 int c,
+		 size_t len,
+		 u32 offset,
+		 u32 buf_sz)
+{
+	if (buf_sz && offset + len > buf_sz) {
+		pr_err("%s: overflow detected, skipping. Try increasing the buffer size",
+		       __func__);
+		return 0;
+	}
+
+	memset(to, c, len);
+	return len;
+}
diff --git a/drivers/media/test-drivers/vidtv/vidtv_common.h b/drivers/media/test-drivers/vidtv/vidtv_common.h
new file mode 100644
index 0000000000000..64072c010dc66
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_common.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * The Virtual DVB test driver serves as a reference DVB driver and helps
+ * validate the existing APIs in the media subsystem. It can also aid
+ * developers working on userspace applications.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#ifndef VIDTV_COMMON_H
+#define VIDTV_COMMON_H
+
+#include <linux/types.h>
+#include <media/dvb_frontend.h>
+
+u32 vidtv_memcpy(void *to,
+		 const void *from,
+		 size_t len,
+		 u32 offset,
+		 u32 buf_sz);
+
+u32 vidtv_memset(void *to,
+		 int c,
+		 size_t len,
+		 u32 offset,
+		 u32 buf_sz);
+
+#endif // VIDTV_COMMON_H
-- 
2.26.2