Skip to contentSkip to conversation

FAILED: patch "[PATCH] nl80211: validate beacon head" failed to apply to 4.4-stable tree

PATCH [email protected] 1 participant 1 message Oct 8, 2019

Subsystems (2)
Stable branch 802.11 (including cfg80211/NL80211)
lore
Share & tools
lore

[email protected]

author maintainer
#0 lore raw

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f88eb7c0d002a67ef31aeb7850b42ff69abc46dc Mon Sep 17 00:00:00 2001
From: Johannes Berg <[email protected]>
Date: Fri, 20 Sep 2019 21:54:17 +0200
Subject: [PATCH] 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 [email protected]
Fixes ed1b6cc7f80f ("cfg80211/nl80211: add beacon settings")
Link https://lore.kernel.org/r/1569009255-I7ac7fbe9436e9d8733439eab8acbbd35e55c74ef@changeid open here
Signed-off-by Johannes Berg <[email protected]>
net/wireless/nl80211.c +35 -2
index d21b1581a665..7386421e2ad3 100644
@@ -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),