Copy union directly instead of using memcpy().

Note that in this case, a direct assignment is more readable and
consistent with the subsequent assignments.

This addresses the following -Wstringop-overflow warning seen in s390
with defconfig:
drivers/infiniband/hw/mlx4/main.c:296:33: warning: writing 16 bytes into a region of size 0 [-Wstringop-overflow=]
  296 |                                 memcpy(&port_gid_table->gids[free].gid,
      |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  297 |                                        &attr->gid, sizeof(attr->gid));
      |                                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This helps with the ongoing efforts to globally enable
-Wstringop-overflow.

Link: https://github.com/KSPP/linux/issues/308
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 drivers/infiniband/hw/mlx4/main.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/infiniband/hw/mlx4/main.c b/drivers/infiniband/hw/mlx4/main.c
index 216aacd72e4f..2d2cd17e02e6 100644
--- a/drivers/infiniband/hw/mlx4/main.c
+++ b/drivers/infiniband/hw/mlx4/main.c
@@ -293,8 +293,7 @@ static int mlx4_ib_add_gid(const struct ib_gid_attr *attr, void **context)
 				ret = -ENOMEM;
 			} else {
 				*context = port_gid_table->gids[free].ctx;
-				memcpy(&port_gid_table->gids[free].gid,
-				       &attr->gid, sizeof(attr->gid));
+				port_gid_table->gids[free].gid = attr->gid;
 				port_gid_table->gids[free].gid_type = attr->gid_type;
 				port_gid_table->gids[free].vlan_id = vlan_id;
 				port_gid_table->gids[free].ctx->real_index = free;
-- 
2.34.1

On Tue, 15 Aug 2023 14:39:53 -0600, Gustavo A. R. Silva wrote:
> Copy union directly instead of using memcpy().
> 
> Note that in this case, a direct assignment is more readable and
> consistent with the subsequent assignments.
> 
> This addresses the following -Wstringop-overflow warning seen in s390
> with defconfig:
> drivers/infiniband/hw/mlx4/main.c:296:33: warning: writing 16 bytes into a region of size 0 [-Wstringop-overflow=]
>   296 |                                 memcpy(&port_gid_table->gids[free].gid,
>       |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   297 |                                        &attr->gid, sizeof(attr->gid));
>       |                                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> [...]

Applied, thanks!

[1/1] RDMA/mlx4: Copy union directly
      https://git.kernel.org/rdma/rdma/c/18ddaeb03bdb65

Best regards,
-- 
Leon Romanovsky <leon@kernel.org>

On Tue, Aug 15, 2023 at 02:39:53PM -0600, Gustavo A. R. Silva wrote:
> Copy union directly instead of using memcpy().
> 
> Note that in this case, a direct assignment is more readable and
> consistent with the subsequent assignments.
> 
> This addresses the following -Wstringop-overflow warning seen in s390
> with defconfig:
> drivers/infiniband/hw/mlx4/main.c:296:33: warning: writing 16 bytes into a region of size 0 [-Wstringop-overflow=]
>   296 |                                 memcpy(&port_gid_table->gids[free].gid,
>       |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   297 |                                        &attr->gid, sizeof(attr->gid));
>       |                                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Hm, why did it think the union had a size of 0?

Regardless, it's a nice fix:

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook