CVE-2022-48744
Publication date:
20/06/2024
In the Linux kernel, the following vulnerability has been resolved:<br />
<br />
net/mlx5e: Avoid field-overflowing memcpy()<br />
<br />
In preparation for FORTIFY_SOURCE performing compile-time and run-time<br />
field bounds checking for memcpy(), memmove(), and memset(), avoid<br />
intentionally writing across neighboring fields.<br />
<br />
Use flexible arrays instead of zero-element arrays (which look like they<br />
are always overflowing) and split the cross-field memcpy() into two halves<br />
that can be appropriately bounds-checked by the compiler.<br />
<br />
We were doing:<br />
<br />
#define ETH_HLEN 14<br />
#define VLAN_HLEN 4<br />
...<br />
#define MLX5E_XDP_MIN_INLINE (ETH_HLEN + VLAN_HLEN)<br />
...<br />
struct mlx5e_tx_wqe *wqe = mlx5_wq_cyc_get_wqe(wq, pi);<br />
...<br />
struct mlx5_wqe_eth_seg *eseg = &wqe->eth;<br />
struct mlx5_wqe_data_seg *dseg = wqe->data;<br />
...<br />
memcpy(eseg->inline_hdr.start, xdptxd->data, MLX5E_XDP_MIN_INLINE);<br />
<br />
target is wqe->eth.inline_hdr.start (which the compiler sees as being<br />
2 bytes in size), but copying 18, intending to write across start<br />
(really vlan_tci, 2 bytes). The remaining 16 bytes get written into<br />
wqe->data[0], covering byte_count (4 bytes), lkey (4 bytes), and addr<br />
(8 bytes).<br />
<br />
struct mlx5e_tx_wqe {<br />
struct mlx5_wqe_ctrl_seg ctrl; /* 0 16 */<br />
struct mlx5_wqe_eth_seg eth; /* 16 16 */<br />
struct mlx5_wqe_data_seg data[]; /* 32 0 */<br />
<br />
/* size: 32, cachelines: 1, members: 3 */<br />
/* last cacheline: 32 bytes */<br />
};<br />
<br />
struct mlx5_wqe_eth_seg {<br />
u8 swp_outer_l4_offset; /* 0 1 */<br />
u8 swp_outer_l3_offset; /* 1 1 */<br />
u8 swp_inner_l4_offset; /* 2 1 */<br />
u8 swp_inner_l3_offset; /* 3 1 */<br />
u8 cs_flags; /* 4 1 */<br />
u8 swp_flags; /* 5 1 */<br />
__be16 mss; /* 6 2 */<br />
__be32 flow_table_metadata; /* 8 4 */<br />
union {<br />
struct {<br />
__be16 sz; /* 12 2 */<br />
u8 start[2]; /* 14 2 */<br />
} inline_hdr; /* 12 4 */<br />
struct {<br />
__be16 type; /* 12 2 */<br />
__be16 vlan_tci; /* 14 2 */<br />
} insert; /* 12 4 */<br />
__be32 trailer; /* 12 4 */<br />
}; /* 12 4 */<br />
<br />
/* size: 16, cachelines: 1, members: 9 */<br />
/* last cacheline: 16 bytes */<br />
};<br />
<br />
struct mlx5_wqe_data_seg {<br />
__be32 byte_count; /* 0 4 */<br />
__be32 lkey; /* 4 4 */<br />
__be64 addr; /* 8 8 */<br />
<br />
/* size: 16, cachelines: 1, members: 3 */<br />
/* last cacheline: 16 bytes */<br />
};<br />
<br />
So, split the memcpy() so the compiler can reason about the buffer<br />
sizes.<br />
<br />
"pahole" shows no size nor member offset changes to struct mlx5e_tx_wqe<br />
nor struct mlx5e_umr_wqe. "objdump -d" shows no meaningful object<br />
code changes (i.e. only source line number induced differences and<br />
optimizations).
Severity CVSS v4.0: Pending analysis
Last modification:
21/01/2026
