ipw2x00: 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.

libipw_read_qos_param_element() copies a struct libipw_info_element
into a struct libipw_qos_information_element, but is actually wanting to
copy into the larger struct libipw_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 libipw_info_element {
        u8 id;
        u8 len;
        u8 data[];
} __packed;

struct libipw_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 libipw_qos_parameter_info {
        struct libipw_qos_information_element info_element;
        u8 reserved;
        struct libipw_qos_ac_parameter ac_params_record[QOS_QUEUE_NUM];
} __packed;

Cc: Stanislav Yakovlev <stas.yakovlev@gmail.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210819202825.3545692-2-keescook@chromium.org

diff --git a/drivers/net/wireless/intel/ipw2x00/libipw_rx.c b/drivers/net/wireless/intel/ipw2x00/libipw_rx.c
index 5a2a723..7a684b7 100644 (file)
--- a/drivers/net/wireless/intel/ipw2x00/libipw_rx.c
+++ b/drivers/net/wireless/intel/ipw2x00/libipw_rx.c
@@ -927,7 +927,8 @@ static u8 qos_oui[QOS_OUI_LEN] = { 0x00, 0x50, 0xF2 };
 static int libipw_verify_qos_info(struct libipw_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))
@@ -943,57 +944,34 @@ static int libipw_verify_qos_info(struct libipw_qos_information_element
 /*
  * Parse a QoS parameter element
  */
-static int libipw_read_qos_param_element(struct libipw_qos_parameter_info
-                                           *element_param, struct libipw_info_element
-                                           *info_element)
+static int libipw_read_qos_param_element(
+                       struct libipw_qos_parameter_info *element_param,
+                       struct libipw_info_element *info_element)
 {
-       int ret = 0;
-       u16 size = sizeof(struct libipw_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 = libipw_verify_qos_info(&element_param->info_element,
-                                               QOS_OUI_PARAM_SUB_TYPE);
-       return ret;
+       memcpy(element_param, info_element, size);
+       return libipw_verify_qos_info(&element_param->info_element,
+                                     QOS_OUI_PARAM_SUB_TYPE);
 }
 
 /*
  * Parse a QoS information element
  */
-static int libipw_read_qos_info_element(struct
-                                          libipw_qos_information_element
-                                          *element_info, struct libipw_info_element
-                                          *info_element)
+static int libipw_read_qos_info_element(
+                       struct libipw_qos_information_element *element_info,
+                       struct libipw_info_element *info_element)
 {
-       int ret = 0;
-       u16 size = sizeof(struct libipw_qos_information_element) - 2;
+       size_t size = sizeof(struct libipw_qos_information_element) - 2;
 
-       if (element_info == NULL)
+       if (!element_info || !info_element || info_element->len != size - 2)
                return -1;
-       if (info_element == NULL)
-               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 = libipw_verify_qos_info(element_info,
-                                               QOS_OUI_INFO_SUB_TYPE);
-       return ret;
+       memcpy(element_info, info_element, size);
+       return libipw_verify_qos_info(element_info, QOS_OUI_INFO_SUB_TYPE);
 }
 
 /*