netdev - RE: [PATCHv3 net-next 4/4] sctp: implement sender-side procedures for Add Incoming/Outgoing Streams Request Parameter

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Date:   Mon, 23 Jan 2017 11:25:56 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Xin Long' <lucien.xin@...il.com>,
        network dev <netdev@...r.kernel.org>,
        "linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>
CC:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Neil Horman <nhorman@...driver.com>,
        Vlad Yasevich <vyasevich@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>
Subject: RE: [PATCHv3 net-next 4/4] sctp: implement sender-side procedures
 for Add Incoming/Outgoing Streams Request Parameter

From: Xin Long
> Sent: 19 January 2017 17:19
> This patch is to implement Sender-Side Procedures for the Add
> Outgoing and Incoming Streams Request Parameter described in
> rfc6525 section 5.1.5-5.1.6.
> 
> It is also to add sockopt SCTP_ADD_STREAMS in rfc6525 section
> 6.3.4 for users.
...
> +	out = params->sas_outstrms;
> +	in  = params->sas_instrms;
> +
> +	if (!out && !in)
> +		goto out;
> +
> +	if (out) {
> +		__u16 nums = stream->outcnt + out;

Make nums 'unsigned int', the code will be smaller and you can
use the value for the overflow check.

> +		/* Check for overflow, can't use nums here */
> +		if (stream->outcnt + out > SCTP_MAX_STREAM)
> +			goto out;
> +
> +		/* Use ksize to check if stream array really needs to realloc */
> +		if (ksize(stream->out) / sizeof(*stream->out) < nums) {
> +			struct sctp_stream_out *streamout;
> +
> +			streamout = kcalloc(nums, sizeof(*streamout),
> +					    GFP_KERNEL);
> +			if (!streamout) {
> +				retval = -ENOMEM;
> +				goto out;
> +			}
> +
> +			memcpy(streamout, stream->out,
> +			       sizeof(*streamout) * stream->outcnt);
> +
> +			kfree(stream->out);
> +			stream->out = streamout;
> +		}

Does kcalloc() zero the entire area, or just the length you ask for?
If the latter you need to zero the rest here.
...

	David