[PATCH 11/64] net/mlx5e: Avoid field-overflowing memcpy()

Kees Cook
2021-07-27T20:59:36Z

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 flexible arrays instead of zero-element arrays (which look like they
are always overflowing) and split the cross-field memcpy() into two halves
that can be appropriately bounds-checked by the compiler.

"pahole" shows no size nor member offset changes to struct mlx5e_tx_wqe
nor struct mlx5e_umr_wqe. "objdump -d" shows no meaningful object
code changes (i.e. only source line number induced differences and
optimizations).

Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/net/ethernet/mellanox/mlx5/core/en.h | 4 ++--
drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c | 4 +++-
2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
index b1b51bbba054..54c014d97db7 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
@@ -204,7 +204,7 @@ static inline int mlx5e_get_max_num_channels(struct mlx5_core_dev *mdev)
struct mlx5e_tx_wqe {
struct mlx5_wqe_ctrl_seg ctrl;
struct mlx5_wqe_eth_seg eth;
- struct mlx5_wqe_data_seg data[0];
+ struct mlx5_wqe_data_seg data[];
};

struct mlx5e_rx_wqe_ll {
@@ -220,7 +220,7 @@ struct mlx5e_umr_wqe {
struct mlx5_wqe_ctrl_seg ctrl;
struct mlx5_wqe_umr_ctrl_seg uctrl;
struct mlx5_mkey_seg mkc;
- struct mlx5_mtt inline_mtts[0];
+ struct mlx5_mtt inline_mtts[];
};

extern const char mlx5e_self_tests[][ETH_GSTRING_LEN];
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
index 2f0df5cc1a2d..2d2364ea13cf 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
@@ -341,8 +341,10 @@ mlx5e_xmit_xdp_frame(struct mlx5e_xdpsq *sq, struct mlx5e_xmit_data *xdptxd,

/* copy the inline part if required */
if (sq->min_inline_mode != MLX5_INLINE_MODE_NONE) {
- memcpy(eseg->inline_hdr.start, xdptxd->data, MLX5E_XDP_MIN_INLINE);
+ memcpy(eseg->inline_hdr.start, xdptxd->data, sizeof(eseg->inline_hdr.start));
eseg->inline_hdr.sz = cpu_to_be16(MLX5E_XDP_MIN_INLINE);
+ memcpy(dseg, xdptxd->data + sizeof(eseg->inline_hdr.start),
+ MLX5E_XDP_MIN_INLINE - sizeof(eseg->inline_hdr.start));
dma_len -= MLX5E_XDP_MIN_INLINE;
dma_addr += MLX5E_XDP_MIN_INLINE;
dseg++;
--
2.30.2