nl80211: Define policy for packet pattern attributes

Define a policy for packet pattern attributes in order to fix a
potential read over the end of the buffer during nla_get_u32()
of the NL80211_PKTPAT_OFFSET attribute.

Note that the data there can always be read due to SKB allocation
(with alignment and struct skb_shared_info at the end), but the
data might be uninitialized. This could be used to leak some data
from uninitialized vmalloc() memory, but most drivers don't allow
an offset (so you'd just get -EINVAL if the data is non-zero) or
just allow it with a fixed value - 100 or 128 bytes, so anything
above that would get -EINVAL. With brcmfmac the limit is 1500 so
(at least) one byte could be obtained.

Cc: stable@kernel.org
Signed-off-by: Peng Xu <pxu@qti.qualcomm.com>
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
[rewrite description based on SKB allocation knowledge]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/nl80211.c

@@ -549,6 +549,14 @@ nl80211_nan_srf_policy[NL80211_NAN_SRF_ATTR_MAX + 1] = {
 	[NL80211_NAN_SRF_MAC_ADDRS] = { .type = NLA_NESTED },
 };
 
+/* policy for packet pattern attributes */
+static const struct nla_policy
+nl80211_packet_pattern_policy[MAX_NL80211_PKTPAT + 1] = {
+	[NL80211_PKTPAT_MASK] = { .type = NLA_BINARY, },
+	[NL80211_PKTPAT_PATTERN] = { .type = NLA_BINARY, },
+	[NL80211_PKTPAT_OFFSET] = { .type = NLA_U32 },
+};
+
 static int nl80211_prepare_wdev_dump(struct sk_buff *skb,
 				     struct netlink_callback *cb,
 				     struct cfg80211_registered_device **rdev,
@@ -10532,7 +10540,8 @@ static int nl80211_set_wowlan(struct sk_buff *skb, struct genl_info *info)
 			u8 *mask_pat;
 
 			nla_parse_nested(pat_tb, MAX_NL80211_PKTPAT, pat,
-					 NULL, info->extack);
+					 nl80211_packet_pattern_policy,
+					 info->extack);
 			err = -EINVAL;
 			if (!pat_tb[NL80211_PKTPAT_MASK] ||
 			    !pat_tb[NL80211_PKTPAT_PATTERN])
@@ -10781,7 +10790,8 @@ static int nl80211_parse_coalesce_rule(struct cfg80211_registered_device *rdev,
 			    rem) {
 		u8 *mask_pat;
 
-		nla_parse_nested(pat_tb, MAX_NL80211_PKTPAT, pat, NULL, NULL);
+		nla_parse_nested(pat_tb, MAX_NL80211_PKTPAT, pat,
+				 nl80211_packet_pattern_policy, NULL);
 		if (!pat_tb[NL80211_PKTPAT_MASK] ||
 		    !pat_tb[NL80211_PKTPAT_PATTERN])
 			return -EINVAL;