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 decd46b3839380d5e0897f3063ceb4e27d625fe2..c1c117fdf318401b0132e02663de86e0c60e9f7f 100644 (file)
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -1227,6 +1227,8 @@ _ieee802_11_parse_elems_crc(const u8 *start, size_t len, bool action,
                                elems->max_idle_period_ie = (void *)pos;
                        break;
                case WLAN_EID_EXTENSION:
+                       if (!elen)
+                               break;
                        if (pos[0] == WLAN_EID_EXT_HE_MU_EDCA &&
                            elen >= (sizeof(*elems->mu_edca_param_set) + 1)) {
                                elems->mu_edca_param_set = (void *)&pos[1];