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>
---
Since this results in no binary differences, I will carry this in my tree
unless someone else wants to pick it up. It's one of the last remaining
clean-ups needed for the next step in memcpy() hardening.
---
 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 7fd33b356cc8..ee7ecb88adc1 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
@@ -208,7 +208,7 @@ 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 8420fe504927..2be4dd7e90a9 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

On 24 Jan 09:22, Kees Cook wrote:
>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>
>---
>Since this results in no binary differences, I will carry this in my tree
>unless someone else wants to pick it up. It's one of the last remaining
>clean-ups needed for the next step in memcpy() hardening.
>---

applied to net-next-mlx5
Thanks,
Saeed.

On Wed, Jan 26, 2022 at 01:28:54PM -0800, Saeed Mahameed wrote:
> On 24 Jan 09:22, Kees Cook wrote:
> > 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>
> > ---
> > Since this results in no binary differences, I will carry this in my tree
> > unless someone else wants to pick it up. It's one of the last remaining
> > clean-ups needed for the next step in memcpy() hardening.
> > ---
> 
> applied to net-next-mlx5

Thanks! How often does net-next-mlx5 flush into net-next?

-- 
Kees Cook

On 26 Jan 14:53, Kees Cook wrote:
>On Wed, Jan 26, 2022 at 01:28:54PM -0800, Saeed Mahameed wrote:
[...]
>> applied to net-next-mlx5
>
>Thanks! How often does net-next-mlx5 flush into net-next?

every couple of days.