[Devel] Re: [PATCH 3/4] Update the UNIX buffer restore code to match the new format saved in the image file

[Serge E. Hallyn]

Quoting Dan Smith (danms at us.ibm.com):
> Signed-off-by: Dan Smith <danms at us.ibm.com>
> ---
>  net/unix/checkpoint.c |   54 ++++++++++++++++++++++++++----------------------
>  1 files changed, 29 insertions(+), 25 deletions(-)
> 
> diff --git a/net/unix/checkpoint.c b/net/unix/checkpoint.c
> index 749673d..c6a1b27 100644
> --- a/net/unix/checkpoint.c
> +++ b/net/unix/checkpoint.c
> @@ -201,7 +201,6 @@ static int sock_read_buffer_sendmsg(struct ckpt_ctx *ctx,
>  	uint8_t peer_shutdown = 0;
>  	void *buf = NULL;
>  	int sndbuf;
> -	int len;
>  	int ret = 0;
> 
>  	memset(&msg, 0, sizeof(msg));
> @@ -210,14 +209,30 @@ static int sock_read_buffer_sendmsg(struct ckpt_ctx *ctx,
>  	if (IS_ERR(h))
>  		return PTR_ERR(h);
> 
> -	len = _ckpt_read_obj_type(ctx, NULL, 0, CKPT_HDR_BUFFER);
> -	if (len < 0) {
> -		ret = len;
> +	if (h->lin_len > SKB_MAX_ALLOC) {
> +		ckpt_debug("socket buffer too big (%u > %lu)\n",
> +			   h->lin_len, SKB_MAX_ALLOC);
> +		ret = -EINVAL;
> +		goto out;
> +	} else if (h->nr_frags != 0) {
> +		ckpt_debug("unix socket claims to have fragments\n");
> +		ret = -EINVAL;
>  		goto out;
> -	} else if (len > SKB_MAX_ALLOC) {
> -		ckpt_debug("Socket buffer too big (%i > %lu)",
> -			   len, SKB_MAX_ALLOC);
> -		ret = -ENOSPC;
> +	}
> +
> +	buf = kmalloc(h->lin_len, GFP_KERNEL);
> +	if (!buf) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +
> +	kvec.iov_len = h->lin_len;
> +	kvec.iov_base = buf;
> +	ret = _ckpt_read_obj_type(ctx, kvec.iov_base,
> +				  h->lin_len, CKPT_HDR_BUFFER);
> +	ckpt_debug("read unix socket buffer %u: %i\n", h->lin_len, ret);
> +	if (ret < h->lin_len) {
> +		ret = -EINVAL;
>  		goto out;
>  	}
> 
> @@ -246,18 +261,6 @@ static int sock_read_buffer_sendmsg(struct ckpt_ctx *ctx,
>  		}
>  	}
> 
> -	kvec.iov_len = len;
> -	buf = kmalloc(len, GFP_KERNEL);
> -	kvec.iov_base = buf;
> -	if (!buf) {
> -		ret = -ENOMEM;
> -		goto out;
> -	}
> -
> -	ret = ckpt_kread(ctx, kvec.iov_base, len);
> -	if (ret < 0)
> -		goto out;
> -
>  	msg.msg_name = addr;
>  	msg.msg_namelen = addrlen;
> 
> @@ -273,15 +276,16 @@ static int sock_read_buffer_sendmsg(struct ckpt_ctx *ctx,
> 
>  	/* Make sure there's room in the send buffer */
>  	sndbuf = sk->sk_sndbuf;
> -	if (((sk->sk_sndbuf - atomic_read(&sk->sk_wmem_alloc)) < len) &&
> +	if (((sk->sk_sndbuf - atomic_read(&sk->sk_wmem_alloc)) < h->lin_len) &&
>  	    capable(CAP_NET_ADMIN))
> -		sk->sk_sndbuf += len;
> +		sk->sk_sndbuf += h->lin_len;
>  	else
>  		sk->sk_sndbuf = sysctl_wmem_max;

Again, should you check whether h->len_len < sysctl_wmem_max before doing
the capable(CAP_NET_ADMIN)?  The goal is to prevent setting PF_SUPERPRIV
in task->flags if it wasn't absolutely necessary.

> 
> -	ret = kernel_sendmsg(sk->sk_socket, &msg, &kvec, 1, len);
> -	ckpt_debug("kernel_sendmsg(%i,%i): %i\n", h->sk_objref, len, ret);
> -	if ((ret > 0) && (ret != len))
> +	ret = kernel_sendmsg(sk->sk_socket, &msg, &kvec, 1, h->lin_len);
> +	ckpt_debug("kernel_sendmsg(%i,%u): %i\n",
> +		   h->sk_objref, h->lin_len, ret);
> +	if ((ret > 0) && (ret != h->lin_len))
>  		ret = -ENOMEM;
> 
>  	sk->sk_sndbuf = sndbuf;
> -- 
> 1.6.2.5
> 
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