staging: rtl8192e: Avoid field-overflowing memcpy()

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memcpy(), memmove(), and memset(), avoid
intentionally writing across neighboring fields.

Split the 3 addr memcpy() into 3 memcpy() calls so the compiler doesn't
think an overflowing memcpy() happens against the addr1 field (the
neighbors are intended to be copied as well).

rtllib_read_qos_param_element() copies a struct rtllib_info_element
into a struct rtllib_qos_information_element, but is actually wanting to
copy into the larger struct rtllib_qos_parameter_info (the contents of
ac_params_record[] is later examined). Refactor the routine to perform
centralized checks, and copy the entire contents directly (since the id
and len members match the elementID and length members):

struct rtllib_info_element {
u8 id;
u8 len;
u8 data[];
} __packed;

struct rtllib_qos_information_element {
u8 elementID;
u8 length;
u8 qui[QOS_OUI_LEN];
u8 qui_type;
u8 qui_subtype;
u8 version;
u8 ac_info;
} __packed;

struct rtllib_qos_parameter_info {
struct rtllib_qos_information_element info_element;
u8 reserved;
struct rtllib_qos_ac_parameter ac_params_record[QOS_QUEUE_NUM];
} __packed;

Cc: Darshan D V <[e-mail]>
Cc: Aditya Srivastava <[e-mail]>
Cc: [e-mail]
Cc: Larry Finger <[e-mail]>
Signed-off-by: Kees Cook <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/rtl8192e/rtllib_crypt_ccmp.c

···
 	pos = (u8 *) hdr;
 	aad[0] = pos[0] & 0x8f;
 	aad[1] = pos[1] & 0xc7;
-	memcpy(aad + 2, hdr->addr1, 3 * ETH_ALEN);
+	memcpy(&aad[2], &hdr->addr1, ETH_ALEN);
+	memcpy(&aad[8], &hdr->addr2, ETH_ALEN);
+	memcpy(&aad[14], &hdr->addr3, ETH_ALEN);
 	pos = (u8 *) &hdr->seq_ctl;
 	aad[20] = pos[0] & 0x0f;
 	aad[21] = 0; /* all bits masked */

drivers/staging/rtl8192e/rtllib_rx.c

···
 				     *info_element, int sub_type)
 {
 
+	if (info_element->elementID != QOS_ELEMENT_ID)
+		return -1;
 	if (info_element->qui_subtype != sub_type)
 		return -1;
 	if (memcmp(info_element->qui, qos_oui, QOS_OUI_LEN))
···
 
 
 /* Parse a QoS parameter element */
-static int rtllib_read_qos_param_element(struct rtllib_qos_parameter_info
-							*element_param,
-					 struct rtllib_info_element
-							*info_element)
+static int rtllib_read_qos_param_element(
+			struct rtllib_qos_parameter_info *element_param,
+			struct rtllib_info_element *info_element)
 {
-	int ret = 0;
-	u16 size = sizeof(struct rtllib_qos_parameter_info) - 2;
+	size_t size = sizeof(*element_param);
 
-	if ((info_element == NULL) || (element_param == NULL))
+	if (!element_param || !info_element || info_element->len != size - 2)
 		return -1;
 
-	if (info_element->id == QOS_ELEMENT_ID && info_element->len == size) {
-		memcpy(element_param->info_element.qui, info_element->data,
-		       info_element->len);
-		element_param->info_element.elementID = info_element->id;
-		element_param->info_element.length = info_element->len;
-	} else
-		ret = -1;
-	if (ret == 0)
-		ret = rtllib_verify_qos_info(&element_param->info_element,
-						QOS_OUI_PARAM_SUB_TYPE);
-	return ret;
+	memcpy(element_param, info_element, size);
+	return rtllib_verify_qos_info(&element_param->info_element,
+				      QOS_OUI_PARAM_SUB_TYPE);
 }
 
 /* Parse a QoS information element */
-static int rtllib_read_qos_info_element(struct rtllib_qos_information_element
-							*element_info,
-					struct rtllib_info_element
-							*info_element)
+static int rtllib_read_qos_info_element(
+			struct rtllib_qos_information_element *element_info,
+			struct rtllib_info_element *info_element)
 {
-	int ret = 0;
-	u16 size = sizeof(struct rtllib_qos_information_element) - 2;
+	size_t size = sizeof(*element_info);
 
-	if (element_info == NULL)
-		return -1;
-	if (info_element == NULL)
+	if (!element_info || !info_element || info_element->len != size - 2)
 		return -1;
 
-	if ((info_element->id == QOS_ELEMENT_ID) &&
-	    (info_element->len == size)) {
-		memcpy(element_info->qui, info_element->data,
-		       info_element->len);
-		element_info->elementID = info_element->id;
-		element_info->length = info_element->len;
-	} else
-		ret = -1;
-
-	if (ret == 0)
-		ret = rtllib_verify_qos_info(element_info,
-					     QOS_OUI_INFO_SUB_TYPE);
-	return ret;
+	memcpy(element_info, info_element, size);
+	return rtllib_verify_qos_info(element_info, QOS_OUI_INFO_SUB_TYPE);
 }