ghsa-932h-84vw-p6cw
Vulnerability from github
Published
2024-06-20 12:31
Modified
2024-06-20 12:31
Details

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).

Show details on source website


{
  "affected": [],
  "aliases": [
    "CVE-2022-48744"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-06-20T12:15:12Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/mlx5e: Avoid field-overflowing memcpy()\n\nIn preparation for FORTIFY_SOURCE performing compile-time and run-time\nfield bounds checking for memcpy(), memmove(), and memset(), avoid\nintentionally writing across neighboring fields.\n\nUse flexible arrays instead of zero-element arrays (which look like they\nare always overflowing) and split the cross-field memcpy() into two halves\nthat can be appropriately bounds-checked by the compiler.\n\nWe were doing:\n\n\t#define ETH_HLEN  14\n\t#define VLAN_HLEN  4\n\t...\n\t#define MLX5E_XDP_MIN_INLINE (ETH_HLEN + VLAN_HLEN)\n\t...\n        struct mlx5e_tx_wqe      *wqe  = mlx5_wq_cyc_get_wqe(wq, pi);\n\t...\n        struct mlx5_wqe_eth_seg  *eseg = \u0026wqe-\u003eeth;\n        struct mlx5_wqe_data_seg *dseg = wqe-\u003edata;\n\t...\n\tmemcpy(eseg-\u003einline_hdr.start, xdptxd-\u003edata, MLX5E_XDP_MIN_INLINE);\n\ntarget is wqe-\u003eeth.inline_hdr.start (which the compiler sees as being\n2 bytes in size), but copying 18, intending to write across start\n(really vlan_tci, 2 bytes). The remaining 16 bytes get written into\nwqe-\u003edata[0], covering byte_count (4 bytes), lkey (4 bytes), and addr\n(8 bytes).\n\nstruct mlx5e_tx_wqe {\n        struct mlx5_wqe_ctrl_seg   ctrl;                 /*     0    16 */\n        struct mlx5_wqe_eth_seg    eth;                  /*    16    16 */\n        struct mlx5_wqe_data_seg   data[];               /*    32     0 */\n\n        /* size: 32, cachelines: 1, members: 3 */\n        /* last cacheline: 32 bytes */\n};\n\nstruct mlx5_wqe_eth_seg {\n        u8                         swp_outer_l4_offset;  /*     0     1 */\n        u8                         swp_outer_l3_offset;  /*     1     1 */\n        u8                         swp_inner_l4_offset;  /*     2     1 */\n        u8                         swp_inner_l3_offset;  /*     3     1 */\n        u8                         cs_flags;             /*     4     1 */\n        u8                         swp_flags;            /*     5     1 */\n        __be16                     mss;                  /*     6     2 */\n        __be32                     flow_table_metadata;  /*     8     4 */\n        union {\n                struct {\n                        __be16     sz;                   /*    12     2 */\n                        u8         start[2];             /*    14     2 */\n                } inline_hdr;                            /*    12     4 */\n                struct {\n                        __be16     type;                 /*    12     2 */\n                        __be16     vlan_tci;             /*    14     2 */\n                } insert;                                /*    12     4 */\n                __be32             trailer;              /*    12     4 */\n        };                                               /*    12     4 */\n\n        /* size: 16, cachelines: 1, members: 9 */\n        /* last cacheline: 16 bytes */\n};\n\nstruct mlx5_wqe_data_seg {\n        __be32                     byte_count;           /*     0     4 */\n        __be32                     lkey;                 /*     4     4 */\n        __be64                     addr;                 /*     8     8 */\n\n        /* size: 16, cachelines: 1, members: 3 */\n        /* last cacheline: 16 bytes */\n};\n\nSo, split the memcpy() so the compiler can reason about the buffer\nsizes.\n\n\"pahole\" shows no size nor member offset changes to struct mlx5e_tx_wqe\nnor struct mlx5e_umr_wqe. \"objdump -d\" shows no meaningful object\ncode changes (i.e. only source line number induced differences and\noptimizations).",
  "id": "GHSA-932h-84vw-p6cw",
  "modified": "2024-06-20T12:31:21Z",
  "published": "2024-06-20T12:31:21Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2022-48744"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8fbdf8c8b8ab82beab882175157650452c46493e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ad5185735f7dab342fdd0dd41044da4c9ccfef67"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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