stack overflow - kernel thread

Breno
2003-09-13T03:19:29Z

Hi .... this worked

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/unistd.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/string.h>
#include <asm/uaccess.h>
#include <asm/errno.h>
#include <asm/mman.h>
#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/processor.h>
#include <asm-i386/vm86.h>

#define THREAD 1
#define STACK_LIMIT 8192

int check_stack()
{
struct task_struct *p = NULL;
struct vm_area_struct *vma;
unsigned long stack_size, stack_addr, stack_ptr;

daemonize();
sprintf(current->comm,"CHECK_STACK");

for(;;schedule())
{
for_each_task(p)
{
if((p->mm != NULL) && (p->pid != 1))
{

stack_addr = p->mm->start_stack;

stack_ptr = p->thread.esp;

vma = find_vma(p->mm,stack_addr);

if(!vma)
return 0;

stack_size = (vma->vm_end - vma->vm_start)/PAGE_SIZE;

if(stack_size >= (STACK_LIMIT - 1024))
{
printk(KERN_CRIT"Process %s pid: %d\n",p->comm,p->pid);
printk(KERN_CRIT"Stack size %lu k\n",stack_size);

vma->vm_flags &= ~(VM_WRITE | VM_GROWSDOWN);

return 0;
}

}
}
}

return 0;
}

int init_module()
{
int th_pid[THREAD];
int i;

for(i = 0;i < THREAD;i++)
th_pid[i] = kernel_thread(check_stack,NULL,CLONE_SIGHAND);

if(th_pid[i] < 0)
printk(KERN_CRIT"Cannot create thread\n");

return 0;
}

void cleanup_module()
{
}

att,
Breno
----- Original Message -----
From: "William Lee Irwin III" <wli@holomorphy.com>
To: "Alan Cox" <alan@lxorguk.ukuu.org.uk>
Cc:
"Breno" <brenosp@brasilsec.com.br>; "Linux Kernel Mailing List"
<linux-kernel@vger.kernel.org>
Sent: Saturday, September 13, 2003 12:25 AM
Subject: Re: stack overflow

> On Sad, 2003-09-13 at 00:06, William Lee Irwin III wrote:
> >> What he actually wants is in-kernel user stack overflow checking, which
> >> is basically impossible since user stacks are demand paged. He's been
> >> told this before and failed to absorb it.
>
> On Sat, Sep 13, 2003 at 12:18:32AM +0100, Alan Cox wrote:
> > We will fault and error on a user stack exceed. You need to use
> > sigaltstack to catch it for obvious reasons. You can also use mmap and
> > drop in red zones on user space stacks
>
> Stack rlimits are fine and we already do those; the rest sounds like
> something userspace has to do.
>
>
> -- wli
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/