Memory corruption in mmap whe accessing more than 4K (Page Size)

[Vinesh Christopher]

I am having a driver which allocates 2MB of contiguous physical memory 
using get_free_pages(). A user-mode program has to access this memory 
using mmap(). The user mode repeatedly opens the driver, mmap the memory
access the memory for some time , then munmaps the memory and closes the 
memory. After some period of time, the kernel / process crashes and panics

If I use only 4K (Page Size) of memory, then it does not happen. Is there 
any restriction or any other way to access them?

struct page *
sample_vma_nopage(struct vm_area_struct *vma,unsigned long address, int
write)
{
	unsigned long offset;
	unsigned long physaddr;
	struct page *page = NOPAGE_SIGBUS;

	/* Compute the offset */
	offset = (address - vma->vm_start) + VMA_OFFSET(vma);

	/* Get the page in the 2MB buffer where the offset begins */	
	physaddr = MyBuffer +offset;
	page = virt_to_page(__va(physaddr));

	/* Increment the count */
	get_page(page);

	return page;
}

struct 
vm_operations_struct sample_vm_ops = 
{
    open	:  sample_vma_open,
    close	:  sample_vma_close,
    nopage	:  sample_vma_nopage,
};

int 
videocap_mmap(struct file *filp, struct vm_area_struct *vma)
{

    /* Check if the offsets are aligned */
    if (VMA_OFFSET(vma) & (PAGE_SIZE-1))                
    {
	TRACE_ERROR("mmap() received unaligned offsets. Cannot map \n"); 
        return -ENXIO; 
    }

    vma->vm_flags |= VM_RESERVED;
    vma->vm_private_data = NULL;
    vma->vm_ops = &sample_vm_ops;
	
    sample_vma_open(vma);
    return 0;
}

Any help will be appreciated

Regards
Samvinesh Christopher

P.S: Iam not in the mailing list. So please CC to me @ [e-mail]