bugtraq - [HOTFIX] setsockopt kernel vulnerability

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Date: 26 Apr 2004 09:46:26 -0000
From: nolife <nolife@...segv.cc>
To: bugtraq@...urityfocus.com
Subject: [HOTFIX] setsockopt kernel vulnerability




Thought i publish the code so it has more use than idling on a single box. It should patch against the latest bug in setsockopt without the need of a new kernel/reboot.
It logs process and uid if someone tries to exploit the system. 
I've tested it against the public POC, seems to work fine. 

It can be downloaded here: http://sigsegv.cc/setsockopt.c 
Or copy/paste from here:

---------------------------------------------------------------------------
/* setsockopt hotfix by nolife.
 * gcc -c -O3 -fomit-frame-pointer setsockopt.c
   This is a hotfix against the latest kernel vulnerability (integer
overflow in memory size calculation)
   It protects against the POC and should protect against upcoming exploits.
 */
#include <linux/autoconf.h>
#ifdef CONFIG_SMP
#define __SMP__
#endif
#define MODULE
#define __KERNEL__
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/mman.h>
#include <linux/in.h>
#include <linux/net.h>
#include <asm/unistd.h>
#include <asm/uaccess.h>
#include <sys/syscall.h>
#ifdef MODULE_LICENSE
MODULE_LICENSE("GPL");
#endif


#ifndef MCAST_MSFILTER     // you probably do not even have multicast
support .....
 #define MCAST_MSFILTER 48
#endif
#ifndef SYS_SOCKETCALL
 #define SYS_SOCKETCALL 102
#endif
#ifndef SYS_SETSOCKOPT
 #define SYS_SETSOCKOPT 14
#endif
#define AL(x) ((x) * sizeof(unsigned long))

static unsigned char nargs[18]={AL(0),AL(3),AL(3),AL(3),AL(2),AL(3),
                                AL(3),AL(3),AL(4),AL(4),AL(4),AL(6),
                                AL(6),AL(2),AL(5),AL(5),AL(3),AL(3)};
#undef AL
extern void *sys_call_table[];
const int optmem_max = sizeof(unsigned long)*(2*UIO_MAXIOV + 512); 
static long (*old_socketcall)(int call, unsigned long *args); static long new_socketcall(int call,unsigned long *args) 
{
  unsigned long a[6];
  unsigned long a0,a1;
	if (call == SYS_SETSOCKOPT)
	{
        	if (copy_from_user(a, args, nargs[call]))
                	return -EFAULT;
		a0=a[0];
		a1=a[1];
		//printk("setsockopt called with optlen= %d by
%s\n",(int)a[4],current->comm);
		if ((int)a[2] ==  MCAST_MSFILTER)
		{
		// Multicast option
			if ((int)a[4] > optmem_max)
			{
				printk(KERN_ALERT "setsockopt exploit halted. abused by uid %d with
process %.32s\n",current->uid, current->comm);
				return(-ENOBUFS);
			}
		}


 	}
	return old_socketcall(call,args);
}

int init_module()

{
	unsigned long flags;
save_flags(flags);
cli();

old_socketcall = sys_call_table[SYS_SOCKETCALL];
sys_call_table[SYS_SOCKETCALL] = new_socketcall;

restore_flags(flags);
printk(KERN_NOTICE "\"setsockopt\" hotfix loaded (c)nolife\n"); return 0;

}
void cleanup_module()

{
	unsigned long flags;
save_flags(flags);
cli();

sys_call_table[SYS_SOCKETCALL] = old_socketcall;
printk(KERN_NOTICE "\"setsockopt\" hotfix unloaded\n"); restore_flags(flags);

}
---------------------------------------------------------------------------best regards,
nolife ;)