From 9eec2aca63328997846b52e91e88dab94ccd1414 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Fri, 20 Sep 2019 21:54:17 +0200 Subject: [PATCH] nl80211: validate beacon head commit f88eb7c0d002a67ef31aeb7850b42ff69abc46dc upstream. 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. Fixes: ed1b6cc7f80f ("cfg80211/nl80211: add beacon settings") Link: https://lore.kernel.org/r/1569009255-I7ac7fbe9436e9d8733439eab8acbbd35e55c74ef@changeid Signed-off-by: Johannes Berg Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- net/wireless/nl80211.c | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c index 105fdd8589d7b..d82d35aec0ee4 100644 --- a/net/wireless/nl80211.c +++ b/net/wireless/nl80211.c @@ -208,6 +208,36 @@ 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) +{ + 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: + return -EINVAL; +} + /* policy for the attributes */ static const struct nla_policy nl80211_policy[NL80211_ATTR_MAX+1] = { [NL80211_ATTR_WIPHY] = { .type = NLA_U32 }, @@ -3125,6 +3155,11 @@ static int nl80211_parse_beacon(struct nlattr *attrs[], memset(bcn, 0, sizeof(*bcn)); if (attrs[NL80211_ATTR_BEACON_HEAD]) { + int ret = validate_beacon_head(attrs[NL80211_ATTR_BEACON_HEAD]); + + if (ret) + return ret; + bcn->head = nla_data(attrs[NL80211_ATTR_BEACON_HEAD]); bcn->head_len = nla_len(attrs[NL80211_ATTR_BEACON_HEAD]); if (!bcn->head_len) -- 2.47.2