msg not getting printed in struct msghdr in linux kernel - linux

Question

I am using kernel 4.5.3 , and i am working on to implement new Layer 4 transport protocol (essentially a new socket). From user space app, when i send data through my new socket, i am receiving it in kernel. In kernel i am trying to unwrap the buffer and trying to verify if all is correct. The user data send from user space is wrapped into struct msghdr structure by socket layer of linux kernel (so i this portion has to be bug free). It is this structure i am trying to print in my kernel handler of the new socket specific sendmsg fn. Though i am able to print all the fields, except when i print the actual msg send (char *) , it is printing blank.
Below is the dump fn i have written:
static
void dump_msg_hdr(struct msghdr *msg){
struct sockaddr_in *dest_addr = NULL;
struct in_addr dest_ip;
char ipv4[32], *usermsg = NULL;
struct iovec *iov = NULL;
memset(&dest_addr, 0, sizeof(struct sockaddr_in));
memset(&dest_ip, 0, sizeof(struct in_addr));
dest_addr = (struct sockaddr_in *)msg->msg_name;
dest_ip = dest_addr->sin_addr;
getDotDecimalIpV4(htonl(dest_ip.s_addr), ipv4);
printk(KERN_INFO "Dest ip address = %s", ipv4);
iov = msg->msg_iter.iov;
usermsg = (char *)kmalloc(iov->iov_len, GFP_USER);
memcpy(usermsg, iov->iov_base, iov->iov_len);
printk(KERN_INFO "user msg = %s\n", usermsg);
printk(KERN_INFO "msg->msg_iter.count (no of data bytes) = %d", msg->msg_iter.count);
printk(KERN_INFO "iov_base = 0x%x, iov_len = %d\n", iov->iov_base, iov->iov_len);
printk(KERN_INFO "msg->msg_iter.nr_segs (no of iovec segments) = %d", msg->msg_iter.nr_segs);
kfree(usermsg);
}
output
Dest ip address = 192.168.6.6
user msg = <blank>
sg->msg_iter.count (no of data bytes) = 27
iov_base = 0xbf95c153, iov_len = 27
msg->msg_iter.nr_segs (no of iovec segments) = 1
structures
struct iov_iter {
int type;
size_t iov_offset;
size_t count;
const struct iovec *iov; /* SIMPLIFIED - see below */
unsigned long nr_segs;
};
47 struct msghdr {
48 void *msg_name; /* ptr to socket address structure */
49 int msg_namelen; /* size of socket address structure */
50 struct iov_iter msg_iter; /* data */
51 void *msg_control; /* ancillary data */
52 __kernel_size_t msg_controllen; /* ancillary data buffer length */
53 unsigned int msg_flags; /* flags on received message */
54 struct kiocb *msg_iocb; /* ptr to iocb for async requests */
55 };