rtnetlink: Fix message size calculation for link messages (369cf77a) · Commits · 戴 / test

nlmsg_total_size() calculates the length of a netlink message including header and alignment. nla_total_size() calculates the space an individual attribute consumes which was meant to be used in this context. Also, ensure to account for the attribute header for the IFLA_INFO_XSTATS attribute as implementations of get_xstats_size() seem to assume that we do so. The addition of two message headers minus the missing attribute header resulted in a calculated message size that was larger than required. Therefore we never risked running out of skb tailroom. Signed-off-by:

Thomas Graf <tgraf@infradead.org> Acked-by:

Patrick McHardy <kaber@trash.net> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

+5 −4

Original line number	Original line	Diff line number	Diff line
	@@ -347,16 +347,17 @@ static size_t rtnl_link_get_size(const struct net_device *dev)
	if (!ops)		if (!ops)
	return 0;		return 0;

	size = nlmsg_total_size(sizeof(struct nlattr)) + /* IFLA_LINKINFO */		size = nla_total_size(sizeof(struct nlattr)) + /* IFLA_LINKINFO */
	nlmsg_total_size(strlen(ops->kind) + 1); /* IFLA_INFO_KIND */		nla_total_size(strlen(ops->kind) + 1); /* IFLA_INFO_KIND */

	if (ops->get_size)		if (ops->get_size)
	/* IFLA_INFO_DATA + nested data */		/* IFLA_INFO_DATA + nested data */
	size += nlmsg_total_size(sizeof(struct nlattr)) +		size += nla_total_size(sizeof(struct nlattr)) +
	ops->get_size(dev);		ops->get_size(dev);

	if (ops->get_xstats_size)		if (ops->get_xstats_size)
	size += ops->get_xstats_size(dev); /* IFLA_INFO_XSTATS */		/* IFLA_INFO_XSTATS */
			size += nla_total_size(ops->get_xstats_size(dev));

	return size;		return size;
	}		}

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