[PATCH v2 21/63] net/mlx5e: Use struct_group() for memcpy() region

Kees Cook
2021-08-18T06:24:47Z

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 vlan_ethhdr around members h_dest and
h_source, 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 h_dest.

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

Cc: Saeed Mahameed <saeedm@nvidia.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Cc: linux-rdma@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/net/ethernet/mellanox/mlx5/core/en_tx.c | 2 +-
include/linux/if_vlan.h | 6 ++++--
2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
index c63d78eda606..39942a952736 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
@@ -207,7 +207,7 @@ static inline void mlx5e_insert_vlan(void *start, struct sk_buff *skb, u16 ihs)
int cpy1_sz = 2 * ETH_ALEN;
int cpy2_sz = ihs - cpy1_sz;

- memcpy(vhdr, skb->data, cpy1_sz);
+ memcpy(&vhdr->addrs, skb->data, cpy1_sz);
vhdr->h_vlan_proto = skb->vlan_proto;
vhdr->h_vlan_TCI = cpu_to_be16(skb_vlan_tag_get(skb));
memcpy(&vhdr->h_vlan_encapsulated_proto, skb->data + cpy1_sz, cpy2_sz);
diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h
index 41a518336673..45aad461aa34 100644
--- a/include/linux/if_vlan.h
+++ b/include/linux/if_vlan.h
@@ -46,8 +46,10 @@ struct vlan_hdr {
* @h_vlan_encapsulated_proto: packet type ID or len
*/
struct vlan_ethhdr {
- unsigned char h_dest[ETH_ALEN];
- unsigned char h_source[ETH_ALEN];
+ struct_group(addrs,
+ unsigned char h_dest[ETH_ALEN];
+ unsigned char h_source[ETH_ALEN];
+ );
__be16 h_vlan_proto;
__be16 h_vlan_TCI;
__be16 h_vlan_encapsulated_proto;
--
2.30.2