CODEWITHSUNDEEP
clinux-kerneloperating-systemlinked-listkernel
Alex
Alex

Reputation: 27

Kernel Linked List Kernel Oops

I'm trying to create a Linked List using linux/list.h in the Kernel level. My code compiles but when I try to add more than one Nodes into the linked list it causes a Kernel Oops. Here is my Kernel Level Code:

    //global defs
    struct Node {
char *data;
    struct list_head list;
    };
    LIST_HEAD(mylinkedlist);
    DEFINE_MUTEX(mut);

    asmlinkage long write(const void __user *data, long len){
    //create new space in memory enough to fit data
    void *ptr = kmalloc(len, GFP_KERNEL);
    //create the user space pointer to kernel space pointer
    int verif = copy_from_user(ptr, data, len);
    if(verif != 0){
            return -EFAULT;
    }


    struct Node first = {ptr, LIST_HEAD_INIT(first.list)};
    //wait for mutex to be available
    mutex_lock_interruptible(&mut);
    list_add_tail(&first.list, &mylinkedlist);
    //release the mutex
    mutex_unlock(&mut);

    return 0;

and my userland program looks like:

long hello_syscall(void) {
char *arg = "Hello";
return syscall(351, "Hello", sizeof(arg));
}

It all compiles but when I try and run the userland program more than once it gives shows that I have a kernel oops. I've created a gist of the error message that the OS gives me when it occurs: https://gist.github.com/anonymous/7217210

Upvotes: 1

Views: 621

Answers (2)

Hossein Kardgar
Hossein Kardgar

Reputation: 7

Linux kernel is mostly written in the C language. And you can use structure in this shape : 

struct _Node
 {

    char *data;
    struct NODE* list;

}NODE,PNODE*;

Upvotes: 0

ensc
ensc

Reputation: 6984

struct Node first = {ptr, LIST_HEAD_INIT(first.list)};

allocates first on the stack and it vanishes when function is left. mylinkedlist will point to garbage hence and next list operation will crash.

Upvotes: 1

Related Questions