[PATCH] libertas_tf: Use struct_group() for memcpy() region

[PATCH] libertas_tf: Use struct_group() for memcpy() region

[Kees Cook]

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

Use struct_group() in struct txpd around members tx_dest_addr_high
and tx_dest_addr_low 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 tx_dest_addr_high.

"pahole" shows no size nor member offset changes to struct txpd.
"objdump -d" shows no object code changes.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/net/wireless/marvell/libertas_tf/libertas_tf.h | 10 ++++++----
 drivers/net/wireless/marvell/libertas_tf/main.c        |  3 ++-
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/marvell/libertas_tf/libertas_tf.h b/drivers/net/wireless/marvell/libertas_tf/libertas_tf.h
index 5d726545d987..b2af2ddb6bc4 100644
--- a/drivers/net/wireless/marvell/libertas_tf/libertas_tf.h
+++ b/drivers/net/wireless/marvell/libertas_tf/libertas_tf.h
@@ -268,10 +268,12 @@ struct txpd {
 	__le32 tx_packet_location;
 	/* Tx packet length */
 	__le16 tx_packet_length;
-	/* First 2 byte of destination MAC address */
-	u8 tx_dest_addr_high[2];
-	/* Last 4 byte of destination MAC address */
-	u8 tx_dest_addr_low[4];
+	struct_group(tx_dest_addr,
+		/* First 2 byte of destination MAC address */
+		u8 tx_dest_addr_high[2];
+		/* Last 4 byte of destination MAC address */
+		u8 tx_dest_addr_low[4];
+	);
 	/* Pkt Priority */
 	u8 priority;
 	/* Pkt Trasnit Power control */
diff --git a/drivers/net/wireless/marvell/libertas_tf/main.c b/drivers/net/wireless/marvell/libertas_tf/main.c
index 71492211904b..02a1e1f547d8 100644
--- a/drivers/net/wireless/marvell/libertas_tf/main.c
+++ b/drivers/net/wireless/marvell/libertas_tf/main.c
@@ -232,7 +232,8 @@ static void lbtf_tx_work(struct work_struct *work)
 			     ieee80211_get_tx_rate(priv->hw, info)->hw_value);
 
 	/* copy destination address from 802.11 header */
-	memcpy(txpd->tx_dest_addr_high, skb->data + sizeof(struct txpd) + 4,
+	BUILD_BUG_ON(sizeof(txpd->tx_dest_addr) != ETH_ALEN);
+	memcpy(&txpd->tx_dest_addr, skb->data + sizeof(struct txpd) + 4,
 		ETH_ALEN);
 	txpd->tx_packet_length = cpu_to_le16(len);
 	txpd->tx_packet_location = cpu_to_le32(sizeof(struct txpd));
-- 
2.30.2

Re: [PATCH] libertas_tf: Use struct_group() for memcpy() region

[Kalle Valo]

Kees Cook <keescook@chromium.org> wrote:

> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field array bounds checking for memcpy(), memmove(), and memset(),
> avoid intentionally writing across neighboring fields.
> 
> Use struct_group() in struct txpd around members tx_dest_addr_high
> and tx_dest_addr_low 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 tx_dest_addr_high.
> 
> "pahole" shows no size nor member offset changes to struct txpd.
> "objdump -d" shows no object code changes.
> 
> Signed-off-by: Kees Cook <keescook@chromium.org>

Patch applied to wireless-drivers-next.git, thanks.

642a57475b30 libertas_tf: Use struct_group() for memcpy() region

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20211118184121.1283821-1-keescook@chromium.org/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches