cfg80211_is_element_inherited() reads the first data octet of the candidate element (id = elem->data[0]) to look it up in an extension non-inheritance list. It does so after testing elem->id, but without verifying that the element actually has a data octet. A zero-length extension element (WLAN_EID_EXTENSION with length 0) therefore makes it read one octet past the end of the element. _ieee802_11_parse_elems_full() runs this check for every element of a frame once a non-inheritance context exists -- e.g. while parsing a per-STA profile of a Multi-Link element in a (re)association response, or a non-transmitted BSS profile -- so a crafted frame from an AP can trigger a one-octet slab-out-of-bounds read during element parsing: BUG: KASAN: slab-out-of-bounds in cfg80211_is_element_inherited Read of size 1 ... in net/wireless/scan.c Return early (treat the element as inherited) when an extension element carries no data, mirroring the existing handling of empty ID lists. The bug was found by fuzzing ieee802_11_parse_elems_full() under KASAN. Fixes: f7dacfb11475 ("cfg80211: support non-inheritance element") Signed-off-by: HE WEI (ギカク) --- Changes in v3: - Move the version changelog below the --- line and trim the Fixes commit id to 12 characters (checkpatch). Changes in v2: - Correct the Fixes tag. The unchecked elem->data[0] read was introduced in 2019 by f7dacfb11475 ("cfg80211: support non-inheritance element") -- the commit that added cfg80211_is_element_inherited() -- not by dfd9aa3e7a45, which only rewrote the sibling cfg80211_gen_new_ie() and never touched this function. net/wireless/scan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/wireless/scan.c b/net/wireless/scan.c index 05b7dc6b7..0a44856b1 100644 --- a/net/wireless/scan.c +++ b/net/wireless/scan.c @@ -205,7 +205,7 @@ bool cfg80211_is_element_inherited(const struct element *elem, return true; if (elem->id == WLAN_EID_EXTENSION) { - if (!ext_id_len) + if (!ext_id_len || !elem->datalen) return true; loop_len = ext_id_len; list = &non_inherit_elem->data[3 + id_len]; -- 2.43.0