Re: copy_to/from_use query?

[mohanlal jangir <mohanlal@xxxxxxxxxxx>]

I have an small program. In this program, a pointer to struct data (in user
space) is received in function make_local_copy (in kernel) using ioctl. In
function make_local_copy, I want to make a local copy using copy_from_usr. I
think, accessing p_usr_data->p_len in second call to copy_from_usr in this
program is incorrect. Can someone confirm it?

struct data {
     int len;
     int *p_len;
};

struct data*  make_local_copy(unsigned long arg) {
     struct data *p_usr_data = (struct data*)arg;
     struct data *p_kernel_data =
          (struct data*) kmalloc(sizeof(struct data), GFP_KERNEL);

     copy_from_usr(p_kernel_data, p_usr_data, sizeof(*p_usr_data));

     p_kernel_data->p_len =
          (int*) kmalloc(p_kernel_data->len, GFP_KERNEL);

     copy_from_usr(p_kernel_data->p_len,
           p_usr_data->p_len, p_kernel_data->len);
        /* ^^^^^^^^^^^^^ */
     return p_kernel_data;
}

Regards
Mohanlal


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