Re: [PATCH] IB/mlx5: Fix a possible null-pointer dereference in set_roce_addr()

[Michael Gur]

On 12/9/2025 9:23 AM, Tuo Li wrote:
> The pointer gid is checked at the beginning of set_roce_addr(). However,
> if it is NULL, the function continues execution and may dereference gid
> when calling mlx5_core_roce_gid_set():
>
>    return mlx5_core_roce_gid_set(..., gid->raw, ...)
>
> This can lead to a null-pointer dereference. To prevent this, add an else
> branch that return -EINVAL when gid is NULL, and remove the redundant gid
> check in the IB_GID_TYPE_ROCE_UDP_ENCAP case.

Can you reproduce this?

Theoretically, gid->raw is translated to NULL+0 which is undefined 
behavior and static analyzers can complain, but it seems compilers just 
translate to NULL which leads us to the expected behavior.

> Signed-off-by: Tuo Li <islituo@xxxxxxxxx>
> ---
>   drivers/infiniband/hw/mlx5/main.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
> index 40284bbb45d6..d68a58d249d4 100644
> --- a/drivers/infiniband/hw/mlx5/main.c
> +++ b/drivers/infiniband/hw/mlx5/main.c
> @@ -645,6 +645,8 @@ int set_roce_addr(struct mlx5_ib_dev *dev, u32 port_num,
>   		ret = rdma_read_gid_l2_fields(attr, &vlan_id, &mac[0]);
>   		if (ret)
>   			return ret;
> +	} else {
> +		return -EINVAL;
>   	}

This breaks the gid deletion, we should still call mlx5_core with NULL 
gid for it to update the table.

>   
>   	switch (gid_type) {
> @@ -653,7 +655,7 @@ int set_roce_addr(struct mlx5_ib_dev *dev, u32 port_num,
>   		break;
>   	case IB_GID_TYPE_ROCE_UDP_ENCAP:
>   		roce_version = MLX5_ROCE_VERSION_2;
> -		if (gid && ipv6_addr_v4mapped((void *)gid))
> +		if (ipv6_addr_v4mapped((void *)gid))
>   			roce_l3_type = MLX5_ROCE_L3_TYPE_IPV4;
>   		else
>   			roce_l3_type = MLX5_ROCE_L3_TYPE_IPV6;