Commit 155fb43b authored by Jakub Kicinski's avatar Jakub Kicinski
Browse files

net: limit altnames to 64k total 



Property list (altname is a link "property") is wrapped
in a nlattr. nlattrs length is 16bit so practically
speaking the list of properties can't be longer than
that, otherwise user space would have to interpret
broken netlink messages.

Prevent the problem from occurring by checking the length
of the property list before adding new entries.

Reported-by: default avatarGeorge Shuklin <george.shuklin@gmail.com>
Reviewed-by: default avatarDavid Ahern <dsahern@kernel.org>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 5d26cff5

net/core/rtnetlink.c

+11 −0
Original line number Diff line number Diff line
@@ -3652,12 +3652,23 @@ static int rtnl_alt_ifname(int cmd, struct net_device *dev, struct nlattr *attr, 
			   bool *changed, struct netlink_ext_ack *extack)

{

	char *alt_ifname;

	size_t size;

	int err;



	err = nla_validate(attr, attr->nla_len, IFLA_MAX, ifla_policy, extack);

	if (err)

		return err;



	if (cmd == RTM_NEWLINKPROP) {

		size = rtnl_prop_list_size(dev);

		size += nla_total_size(ALTIFNAMSIZ);

		if (size >= U16_MAX) {

			NL_SET_ERR_MSG(extack,

				       "effective property list too long");

			return -EINVAL;

		}

	}



	alt_ifname = nla_strdup(attr, GFP_KERNEL_ACCOUNT);

	if (!alt_ifname)

		return -ENOMEM;