CVE-2022-48744 (Moderate severity, published 2024-06-19)
CVSS score: 6.7 (CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H)
CWE: CWE-787
Description: 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).
Mitigation: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.