nl80211: fix beacon head validation

stable inclusion
from stable-5.10.30
commit 42e4450e37905c8765b770c490cd6c64713e5de9
bugzilla: 51791

--------------------------------

commit 9a6847ba upstream.

If the beacon head attribute (NL80211_ATTR_BEACON_HEAD)
is too short to even contain the frame control field,
we access uninitialized data beyond the buffer. Fix this
by checking the minimal required size first. We used to
do this until S1G support was added, where the fixed
data portion has a different size.

Reported-and-tested-by: syzbot+72b99dcf4607e8c770f3@syzkaller.appspotmail.com
Suggested-by: NEric Dumazet <eric.dumazet@gmail.com>
Fixes: 1d47f119 ("nl80211: correctly validate S1G beacon head")
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>
Link: https://lore.kernel.org/r/20210408154518.d9b06d39b4ee.Iff908997b2a4067e8d456b3cb96cab9771d252b8@changeidSigned-off-by: NJohannes Berg <johannes.berg@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: N  Weilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

net/wireless/nl80211.c

@@ -209,9 +209,13 @@ static int validate_beacon_head(const struct nlattr *attr,
 	unsigned int len = nla_len(attr);
 	const struct element *elem;
 	const struct ieee80211_mgmt *mgmt = (void *)data;
-	bool s1g_bcn = ieee80211_is_s1g_beacon(mgmt->frame_control);
 	unsigned int fixedlen, hdrlen;
+	bool s1g_bcn;
 
+	if (len < offsetofend(typeof(*mgmt), frame_control))
+		goto err;
+
+	s1g_bcn = ieee80211_is_s1g_beacon(mgmt->frame_control);
 	if (s1g_bcn) {
 		fixedlen = offsetof(struct ieee80211_ext,
 				    u.s1g_beacon.variable);