cxgb4: Use struct_group() for memcpy() region

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 fw_eth_tx_pkt_vm_wr around members ethmacdst,
ethmacsrc, ethtype, and vlantci, 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 ethmacdst.

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

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/net/ethernet/chelsio/cxgb4/t4fw_api.h b/drivers/net/ethernet/chelsio/cxgb4/t4fw_api.h
index 0a326c054707..2419459a0b85 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/t4fw_api.h
+++ b/drivers/net/ethernet/chelsio/cxgb4/t4fw_api.h
@@ -794,10 +794,12 @@ struct fw_eth_tx_pkt_vm_wr {
 	__be32 op_immdlen;
 	__be32 equiq_to_len16;
 	__be32 r3[2];
-	u8 ethmacdst[6];
-	u8 ethmacsrc[6];
-	__be16 ethtype;
-	__be16 vlantci;
+	struct_group(firmware,
+		u8 ethmacdst[ETH_ALEN];
+		u8 ethmacsrc[ETH_ALEN];
+		__be16 ethtype;
+		__be16 vlantci;
+	);
 };
 
 #define FW_CMD_MAX_TIMEOUT 10000