In user space when you write beyond your address space (if your write crosses
the page boundary alloacted to you), then process is terminated. In the kernel
you are still writinng inside the kernel address space. Your write is not beyond
kernel address space.
Secondly you are corrupting some other data structure. The kernel stack is part
of task_struct of the running process, a kmalloc or slab allocator might have
provided this memory (task_-struct). When you write beyond this if the
write modiefies some crucial data structure that may result in hang or a crash.
On Thu, Sep 13, 2012 at 12:15 PM, shubham sharma <shubham20006@xxxxxxxxx> wrote:
Hi,
As far as i know, the size of stack allocated in the kernel space is
8Kb for each process. But in case i use more than 8Kb of memory from
the stack then what will happen? I think that in that case the system
would crash because i am accessing an illegal memory area. I wrote
kernel module in which i defined an integer array whose size was 8000.
But still it did not crash my system. Why?
The module i wrote was as follows:
#include <linux/kernel.h>
#include <linux/module.h>
int __init init_my_module(void)
{
int arr[8000];
printk("%s:%d\tmodule initilized\n", __func__, __LINE__);
arr[1] = 1;
arr[4000] = 1;
arr[7999] = 1;
printk("%s:%d\tarr[1]:%d, arr[4000]:%d, arr[7999]:%d\n", __func__,
__LINE__, arr[1], arr[4000], arr[7999]);
return 0;
}
void __exit cleanup_my_module(void)
{
printk("exiting\n");
return;
}
module_init(init_my_module);
module_exit(cleanup_my_module);
MODULE_LICENSE("GPL");
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