mac80211: validate extended element ID is present

Before attempting to parse an extended element, verify that
the extended element ID is present.

Fixes: 8888ba3bbf42 ("mac80211: add support for HE")
Reported-by: syzbot+59bdff68edce82e393b6@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/20211211201023.f30a1b128c07.I5cacc176da94ba316877c6e10fe3ceec8b4dbd7d@changeid
Cc: stable@vger.kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 43df2f0c5db9c52b2484196946d2008b22ff3cf0..6c2934854d3cedf293ef568ac0fddd20e8b174b1 100644 (file)
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -943,7 +943,12 @@ static void ieee80211_parse_extension_element(u32 *crc,
                                              struct ieee802_11_elems *elems)
 {
        const void *data = elem->data + 1;
-       u8 len = elem->datalen - 1;
+       u8 len;
+
+       if (!elem->datalen)
+               return;
+
+       len = elem->datalen - 1;
 
        switch (elem->data[0]) {
        case WLAN_EID_EXT_HE_MU_EDCA: