Re: [syzbot] [wireless?] UBSAN: array-index-out-of-bounds in ieee80211_rx_mgmt_beacon

[Edward Adam Davis]

#syz test

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 2d46d4af60d7..c370352b7d7d 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -7222,7 +7222,7 @@ static void ieee80211_rx_mgmt_beacon(struct ieee80211_link_data *link,
 	if (ieee80211_is_s1g_beacon(mgmt->frame_control)) {
 		struct ieee80211_ext *ext = (void *) mgmt;
 		variable = ext->u.s1g_beacon.variable +
-			   ieee80211_s1g_optional_len(ext->frame_control);
+			   (ieee80211_s1g_optional_len(ext->frame_control) - 1);
 	}
 
 	baselen = (u8 *) variable - (u8 *) mgmt;
diff --git a/include/linux/ieee80211.h b/include/linux/ieee80211.h
index ce377f7fb912..556ce95e0b0f 100644
--- a/include/linux/ieee80211.h
+++ b/include/linux/ieee80211.h
@@ -1278,7 +1278,7 @@ struct ieee80211_ext {
 			u8 sa[ETH_ALEN];
 			__le32 timestamp;
 			u8 change_seq;
-			u8 variable[0];
+			u8 variable[4];
 		} __packed s1g_beacon;
 	} u;
 } __packed __aligned(2);