netdev - Re: [PATCH 2/2] [RFC] Add c/r support for connected INET sockets

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Date:	Thu, 08 Oct 2009 14:47:13 +0000
From:	John Dykstra <john.dykstra1@...il.com>
To:	Dan Smith <danms@...ibm.com>
Cc:	containers@...ts.osdl.org, netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] [RFC] Add c/r support for connected INET sockets

On Wed, 2009-10-07 at 09:29 -0700, Dan Smith wrote:
> This patch adds basic support for C/R of open INET sockets.  I think
> that
> all the important bits of the TCP and ICSK socket structures is saved,
> but I think there is still some additional IPv6 stuff that needs to be
> handled.

I think this patch breaks code that was already in do_sock_restore():

        struct sock *do_sock_restore(struct ckpt_ctx *ctx)
        {
        	struct ckpt_hdr_socket *h;
        	struct socket *sock;
        	int ret;

        	h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_SOCKET);
        	if (IS_ERR(h))
        		return ERR_PTR(PTR_ERR(h));

        	/* silently clear flags, e.g. SOCK_NONBLOCK or SOCK_CLOEXEC */
        	h->sock.type &= SOCK_TYPE_MASK;

        	ret = sock_create(h->sock_common.family, h->sock.type, 0, &sock);
        	if (ret < 0)
        		goto err;

You're passing 0 as the protocol value to sock_create().  This
ultimately gets passed to the address family's create() function.  

inet_create() (and its IPv6 companion) use that protocol value as the
key when they search for the proper inet_protosw, which in turn gets
mapped to the struct proto and passed to sk_prot_alloc().

In address families INET and AF_INET6, the struct sock is different
sizes for different protocols.  This is implemented by the struct proto
specifying which cache the struct sock comes from.

So by passing in 0 all the time to sock_create(), you're getting a
struct sock that may not be the right size.  Memory corruption and
madness follow.

  --  John

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