[PATCH 24/64] staging: wlan-ng: Use struct_group() for memcpy() region

[Kees Cook]

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.

Use struct_group() in struct hfa384x_tx_frame around members
frame_control, duration_id, address[1-4], and sequence_control, so they
can be referenced together. This will allow memcpy() and sizeof() to
more easily reason about sizes, improve readability, and avoid future
warnings about writing beyond the end of frame_control.

"pahole" shows no size nor member offset changes to struct
hfa384x_tx_frame. "objdump -d" shows no meaningful object code changes
(i.e. only source line number induced differences.)

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 drivers/staging/wlan-ng/hfa384x.h     | 16 +++++++++-------
 drivers/staging/wlan-ng/hfa384x_usb.c |  4 +++-
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/staging/wlan-ng/hfa384x.h b/drivers/staging/wlan-ng/hfa384x.h
index 88e894dd3568..87eb87e3beab 100644
--- a/drivers/staging/wlan-ng/hfa384x.h
+++ b/drivers/staging/wlan-ng/hfa384x.h
@@ -476,13 +476,15 @@ struct hfa384x_tx_frame {
 
 	/*-- 802.11 Header Information --*/
 
-	u16 frame_control;
-	u16 duration_id;
-	u8 address1[6];
-	u8 address2[6];
-	u8 address3[6];
-	u16 sequence_control;
-	u8 address4[6];
+	struct_group(p80211,
+		u16 frame_control;
+		u16 duration_id;
+		u8 address1[6];
+		u8 address2[6];
+		u8 address3[6];
+		u16 sequence_control;
+		u8 address4[6];
+	);
 	__le16 data_len;		/* little endian format */
 
 	/*-- 802.3 Header Information --*/
diff --git a/drivers/staging/wlan-ng/hfa384x_usb.c b/drivers/staging/wlan-ng/hfa384x_usb.c
index f2a0e16b0318..38aaae7a2d69 100644
--- a/drivers/staging/wlan-ng/hfa384x_usb.c
+++ b/drivers/staging/wlan-ng/hfa384x_usb.c
@@ -2516,7 +2516,9 @@ int hfa384x_drvr_txframe(struct hfa384x *hw, struct sk_buff *skb,
 	cpu_to_le16s(&hw->txbuff.txfrm.desc.tx_control);
 
 	/* copy the header over to the txdesc */
-	memcpy(&hw->txbuff.txfrm.desc.frame_control, p80211_hdr,
+	BUILD_BUG_ON(sizeof(hw->txbuff.txfrm.desc.p80211) !=
+		     sizeof(union p80211_hdr));
+	memcpy(&hw->txbuff.txfrm.desc.p80211, p80211_hdr,
 	       sizeof(union p80211_hdr));
 
 	/* if we're using host WEP, increase size by IV+ICV */
-- 
2.30.2