[CRIU] [PATCH] sk-queue: Use int values in getsockopt

[Cyrill Gorcunov]

On Fri, Jul 13, 2012 at 06:11:43PM +0400, Stanislav Kinsbursky wrote:
> >
> >  | Error (sk-queue.c:102): dump_sk_queue: Can't allocate 171798904800 bytes
> >  | Error (cr-dump.c:1289): Dump files (pid: 2505) failed with -1
> >
> 
> That's strange...
> It looks like kernel bug...
> BTW, here is a part of sock_getsockopt():
> 
> int sock_getsockopt(struct socket *sock, int level, int optname,
>                     char __user *optval, int __user *optlen)
> {
>         struct sock *sk = sock->sk;
> 
>         union {
>                 int val;
>                 struct linger ling;
>                 struct timeval tm;
>         } v;
> 
> <--- SNIP --->
> 
>         memset(&v, 0, sizeof(v));	<=== Doesnt' we zeroing 8 bytes here?
> 
> <--- SNIP --->

The v is on-kernel-stack variable, when the value pushed back
to user space it's done by

	int lv = sizeof(int);
	...
	case SO_SNDBUF:
		v.val = sk->sk_sndbuf;
		break;
	...

	if (len > lv)
		len = lv;
	if (copy_to_user(optval, &v, len))
		return -EFAULT;

so when we pass long (on x86-64) it's 8 bytes, while int is 4 bytes
and we don't clean up hight bits.

	Cyrill