I am writing a test module which uses linkedlist using list.h.
I use list_add to add entries in linkedlist, but when i try to iterate the list i get segmentation fault.
I am providing the code below. Could someone help me to fix the problem.

Code
-------

int init_module()
{
int returnValue ;
returnValue = register_chrdev(22, "xxx", &xxx_fops)))
TestList("hello_world00");
TestList("helloworld11");
IterateList();
return 0;
}

int cleanup_module()
{
unregister_chrdev(22,"xxx");
}

void TestList(char *data_in)
{
struct directoryList dirStruct;
my_memcpy(dirStruct.dirName,data_in,strlen(data_in) +1);
list_add(&dirStruct.list,&initList);
printk(" DATA ADDED %s \n", dirStruct.dirName); // i am receiving this print in the log
}

void IterateList()
{
struct list_head *tmp;
list_for_each(tmp, &initList)
{
struct directoryList *iterateList = list_entry(tmp, struct directoryList, list);
printk( " ITERATELIST DIR VALUE %s \n" , iterateList->dirName);
}

}

/*************** LOG OUTPUT IS PROVIDED BELOW *********************/
DATA ADDED hello_world00
DATA ADDED helloworld11
ITERATELIST DIR VALUE helloworld11
last message repeated 661 times
Unable to handle kernel NULL pointer dereference at virtual address 00000001
printing eip:
e0ade288
.... it goes on ....

Segmentation fault occurs when we try to access the memory area that is not allocated, and this error is very common when playing with pointers and strings, so you better check for the proper memory alocation and check that none of your pointer will point to an invalid address.
If you can't figure out this way you better run it in a debugger and check the status of you pointers and buffers on each itration, Are they propely allocated???

Thank you for your reply cppkid,
I got that working after allocating memory for the local variable used in function 'TestList' using kmalloc.
previos code has been changed to the following (only the changed line is included )

void TestList(char *data_in)
{
struct directoryList * dirStruct = (struct directoryList *) kmalloc(sizeof(struct directoryList),GFP_KERNEL);
}