CVE-2022-48744: In the Linux kernel, the following vulnerability has been resolved:  net/mlx5e: Avoid field-overflowing memcpy()  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.  We were doing:   #define ETH_HLEN  14  #define VLAN_HLEN  4  ...  #define MLX5E_XDP_MIN_INLINE (ETH_HLEN + VLAN_HLEN)  ...         struct mlx5e_tx_wqe      *wqe  = mlx5_wq_cyc_get_wqe(wq, pi);  ...         struct mlx5_wqe_eth_seg  *eseg = &wqe->eth;         struct mlx5_wqe_data_seg *dseg = wqe->data;  ...  memcpy(eseg->inline_hdr.start, xdptxd->data, MLX5E_XDP_MIN_INLINE);  target is wqe->eth.inline_hdr.start (which the compiler sees as being 2 bytes in size), but copying 18, intending to write across start (really vlan_tci, 2 bytes). The remaining 16 bytes get written into wqe->data[0], covering byte_count (4 bytes), lkey (4 bytes), and addr (8 bytes).  struct mlx5e_tx_wqe {         struct mlx5_wqe_ctrl_seg   ctrl;                 /*     0    16 */         struct mlx5_wqe_eth_seg    eth;                  /*    16    16 */         struct mlx5_wqe_data_seg   data[];               /*    32     0 */          /* size: 32, cachelines: 1, members: 3 */         /* last cacheline: 32 bytes */ };  struct mlx5_wqe_eth_seg {         u8                         swp_outer_l4_offset;  /*     0     1 */         u8                         swp_outer_l3_offset;  /*     1     1 */         u8                         swp_inner_l4_offset;  /*     2     1 */         u8                         swp_inner_l3_offset;  /*     3     1 */         u8                         cs_flags;             /*     4     1 */         u8                         swp_flags;            /*     5     1 */         __be16                     mss;                  /*     6     2 */         __be32                     flow_table_metadata;  /*     8     4 */         union {                 struct {                         __be16     sz;                   /*    12     2 */                         u8         start[2];             /*    14     2 */                 } inline_hdr;                            /*    12     4 */                 struct {                         __be16     type;                 /*    12     2 */                         __be16     vlan_tci;             /*    14     2 */                 } insert;                                /*    12     4 */                 __be32             trailer;              /*    12     4 */         };                                               /*    12     4 */          /* size: 16, cachelines: 1, members: 9 */         /* last cacheline: 16 bytes */ };  struct mlx5_wqe_data_seg {         __be32                     byte_count;           /*     0     4 */         __be32                     lkey;                 /*     4     4 */         __be64                     addr;                 /*     8     8 */          /* size: 16, cachelines: 1, members: 3 */         /* last cacheline: 16 bytes */ };  So, split the memcpy() so the compiler can reason about the buffer sizes.  "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).