Commit f88eb7c0 authored by Johannes Berg's avatar Johannes Berg
Browse files

nl80211: validate beacon head 

We currently don't validate the beacon head, i.e. the header,
fixed part and elements that are to go in front of the TIM
element. This means that the variable elements there can be
malformed, e.g. have a length exceeding the buffer size, but
most downstream code from this assumes that this has already
been checked.

Add the necessary checks to the netlink policy.

Cc: stable@vger.kernel.org
Fixes: ed1b6cc7 ("cfg80211/nl80211: add beacon settings")
Link: https://lore.kernel.org/r/1569009255-I7ac7fbe9436e9d8733439eab8acbbd35e55c74ef@changeid


Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent 68ce6688

net/wireless/nl80211.c

+35 −2
Original line number Diff line number Diff line
@@ -201,6 +201,38 @@ cfg80211_get_dev_from_info(struct net *netns, struct genl_info *info) 
	return __cfg80211_rdev_from_attrs(netns, info->attrs);

}



static int validate_beacon_head(const struct nlattr *attr,

				struct netlink_ext_ack *extack)

{

	const u8 *data = nla_data(attr);

	unsigned int len = nla_len(attr);

	const struct element *elem;

	const struct ieee80211_mgmt *mgmt = (void *)data;

	unsigned int fixedlen = offsetof(struct ieee80211_mgmt,

					 u.beacon.variable);



	if (len < fixedlen)

		goto err;



	if (ieee80211_hdrlen(mgmt->frame_control) !=

	    offsetof(struct ieee80211_mgmt, u.beacon))

		goto err;



	data += fixedlen;

	len -= fixedlen;



	for_each_element(elem, data, len) {

		/* nothing */

	}



	if (for_each_element_completed(elem, data, len))

		return 0;



err:

	NL_SET_ERR_MSG_ATTR(extack, attr, "malformed beacon head");

	return -EINVAL;

}



static int validate_ie_attr(const struct nlattr *attr,

			    struct netlink_ext_ack *extack)

{
@@ -338,8 +370,9 @@ const struct nla_policy nl80211_policy[NUM_NL80211_ATTR] = { 


	[NL80211_ATTR_BEACON_INTERVAL] = { .type = NLA_U32 },

	[NL80211_ATTR_DTIM_PERIOD] = { .type = NLA_U32 },

	[NL80211_ATTR_BEACON_HEAD] = { .type = NLA_BINARY,

				       .len = IEEE80211_MAX_DATA_LEN },

	[NL80211_ATTR_BEACON_HEAD] =

		NLA_POLICY_VALIDATE_FN(NLA_BINARY, validate_beacon_head,

				       IEEE80211_MAX_DATA_LEN),

	[NL80211_ATTR_BEACON_TAIL] =

		NLA_POLICY_VALIDATE_FN(NLA_BINARY, validate_ie_attr,

				       IEEE80211_MAX_DATA_LEN),

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