Commit b60b87fc authored by Johannes Berg's avatar Johannes Berg Committed by David S. Miller
Browse files

netlink: add ethernet address policy types 



Commonly, ethernet addresses are just using a policy of
	{ .len = ETH_ALEN }
which leaves userspace free to send more data than it should,
which may hide bugs.

Introduce NLA_EXACT_LEN which checks for exact size, rejecting
the attribute if it's not exactly that length. Also add
NLA_EXACT_LEN_WARN which requires the minimum length and will
warn on longer attributes, for backward compatibility.

Use these to define NLA_POLICY_ETH_ADDR (new strict policy) and
NLA_POLICY_ETH_ADDR_COMPAT (compatible policy with warning);
these are used like this:

    static const struct nla_policy <name>[...] = {
        [NL_ATTR_NAME] = NLA_POLICY_ETH_ADDR,
        ...
    };

Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
Reviewed-by: default avatarMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 568b742a

include/net/netlink.h

+13 −0
Original line number Diff line number Diff line
@@ -181,6 +181,8 @@ enum { 
	NLA_S64,

	NLA_BITFIELD32,

	NLA_REJECT,

	NLA_EXACT_LEN,

	NLA_EXACT_LEN_WARN,

	__NLA_TYPE_MAX,

};
@@ -211,6 +213,10 @@ enum { 
 *                         just like "All other"

 *    NLA_BITFIELD32       Unused

 *    NLA_REJECT           Unused

 *    NLA_EXACT_LEN        Attribute must have exactly this length, otherwise

 *                         it is rejected.

 *    NLA_EXACT_LEN_WARN   Attribute should have exactly this length, a warning

 *                         is logged if it is longer, shorter is rejected.

 *    All other            Minimum length of attribute payload

 *

 * Meaning of `validation_data' field:
@@ -236,6 +242,13 @@ struct nla_policy { 
	void            *validation_data;

};



#define NLA_POLICY_EXACT_LEN(_len)	{ .type = NLA_EXACT_LEN, .len = _len }

#define NLA_POLICY_EXACT_LEN_WARN(_len)	{ .type = NLA_EXACT_LEN_WARN, \

					  .len = _len }



#define NLA_POLICY_ETH_ADDR		NLA_POLICY_EXACT_LEN(ETH_ALEN)

#define NLA_POLICY_ETH_ADDR_COMPAT	NLA_POLICY_EXACT_LEN_WARN(ETH_ALEN)



/**

 * struct nl_info - netlink source information

 * @nlh: Netlink message header of original request

lib/nlattr.c

+7 −1
Original line number Diff line number Diff line
@@ -82,12 +82,18 @@ static int validate_nla(const struct nlattr *nla, int maxtype, 


	BUG_ON(pt->type > NLA_TYPE_MAX);



	if (nla_attr_len[pt->type] && attrlen != nla_attr_len[pt->type]) {

	if ((nla_attr_len[pt->type] && attrlen != nla_attr_len[pt->type]) ||

	    (pt->type == NLA_EXACT_LEN_WARN && attrlen != pt->len)) {

		pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n",

				    current->comm, type);

	}



	switch (pt->type) {

	case NLA_EXACT_LEN:

		if (attrlen != pt->len)

			return -ERANGE;

		break;



	case NLA_REJECT:

		if (pt->validation_data && error_msg)

			*error_msg = pt->validation_data;

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