mac80211: validate extended element ID is present

commit 768c0b19b50665e337c96858aa2b7928d6dcf756 upstream.

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

Fixes: 41cbb0f5a295 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 03ea4f929b9977e45a1ac560ba51daa57d778fe2..2fe71ed9137b0f7402b2b2348241ad8c12b41e8f 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: