staging: rtl8723bs: 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.

Adjust memcpy() destination to be the named structure itself, rather than
the first member, allowing memcpy() to correctly reason about the size.

"objdump -d" shows no object code changes.

Cc: Ross Schmidt <ross.schm.dev@gmail.com>
Cc: Joe Perches <joe@perches.com>
Cc: devel@driverdev.osuosl.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210806201422.2871679-1-keescook@chromium.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8723bs/core/rtw_mlme.c

@@ -2389,7 +2389,7 @@ unsigned int rtw_restructure_ht_ie(struct adapter *padapter, u8 *in_ie, u8 *out_
 	}
 
 	/* fill default supported_mcs_set */
-	memcpy(ht_capie.mcs.rx_mask, pmlmeext->default_supported_mcs_set, 16);
+	memcpy(&ht_capie.mcs, pmlmeext->default_supported_mcs_set, 16);
 
 	/* update default supported_mcs_set */
 	rtw_hal_get_hwreg(padapter, HW_VAR_RF_TYPE, (u8 *)(&rf_type));