staging: rtl8192u: 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).

ieee80211_read_qos_param_element() copies a struct ieee80211_info_element
into a struct ieee80211_qos_information_element, but is actually wanting to
copy into the larger struct ieee80211_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 ieee80211_info_element {
        u8 id;
        u8 len;
        u8 data[];
} __packed;

struct ieee80211_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 ieee80211_qos_parameter_info {
        struct ieee80211_qos_information_element info_element;
        u8 reserved;
        struct ieee80211_qos_ac_parameter ac_params_record[QOS_QUEUE_NUM];
} __packed;

Additionally replace old-style zero-element arrays with flexible arrays.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Pascal Terjan <pterjan@google.com>
Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: devel@driverdev.osuosl.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210806201208.2871467-1-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 14 insertions, 35 deletions

diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_rx.c b/drivers/staging/rtl8192u/ieee80211/ieee80211_rx.c
index b0e01ee65f7f..b58e75932ecd 100644
--- a/drivers/staging/rtl8192u/ieee80211/ieee80211_rx.c
+++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_rx.c
@@ -1310,7 +1310,8 @@ static u8 qos_oui[QOS_OUI_LEN] = { 0x00, 0x50, 0xF2 };
 static int ieee80211_verify_qos_info(struct ieee80211_qos_information_element
 				     *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))
@@ -1327,27 +1328,18 @@ static int ieee80211_verify_qos_info(struct ieee80211_qos_information_element
 /*
  * Parse a QoS parameter element
  */
-static int ieee80211_read_qos_param_element(struct ieee80211_qos_parameter_info
-					    *element_param, struct ieee80211_info_element
-					    *info_element)
+static int ieee80211_read_qos_param_element(
+		struct ieee80211_qos_parameter_info *element_param,
+		struct ieee80211_info_element *info_element)
 {
-	int ret = 0;
-	u16 size = sizeof(struct ieee80211_qos_parameter_info) - 2;
+	size_t size = sizeof(*element_param);
 
-	if (!info_element || !element_param)
+	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 = ieee80211_verify_qos_info(&element_param->info_element,
-						QOS_OUI_PARAM_SUB_TYPE);
-	return ret;
+	memcpy(element_param, info_element, size);
+	return ieee80211_verify_qos_info(&element_param->info_element,
+					 QOS_OUI_PARAM_SUB_TYPE);
 }
 
 /*
@@ -1357,26 +1349,13 @@ static int ieee80211_read_qos_info_element(
 		struct ieee80211_qos_information_element *element_info,
 		struct ieee80211_info_element *info_element)
 {
-	int ret = 0;
-	u16 size = sizeof(struct ieee80211_qos_information_element) - 2;
+	size_t size = sizeof(*element_info);
 
-	if (!element_info)
+	if (!element_info || !info_element || info_element->len != size - 2)
 		return -1;
-	if (!info_element)
-		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 = ieee80211_verify_qos_info(element_info,
-						QOS_OUI_INFO_SUB_TYPE);
-	return ret;
+	memcpy(element_info, info_element, size);
+	return ieee80211_verify_qos_info(element_info, QOS_OUI_INFO_SUB_TYPE);
 }