From: Xiang Mei Date: Sun, 21 Jun 2026 09:35:31 +0000 (-0700) Subject: wifi: mac80211: fix unsol_bcast_probe_resp double free on alloc failure X-Git-Tag: v7.2-rc4~17^2~16^2~37 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1d067abcd37062426c59ec73dbc4e87a63f33fea;p=thirdparty%2Fkernel%2Flinux.git wifi: mac80211: fix unsol_bcast_probe_resp double free on alloc failure ieee80211_set_unsol_bcast_probe_resp() calls kfree_rcu() on the old template before allocating the replacement. If the kzalloc() then fails, it returns -ENOMEM while link->u.ap.unsol_bcast_probe_resp still points at the object already queued for freeing. A later update or AP teardown re-queues that same rcu_head; the second free is caught by KASAN when the RCU sheaf is processed in softirq: BUG: KASAN: double-free in rcu_free_sheaf (mm/slub.c:5850) Free of addr ffff88800d06f300 by task exploit/145 ... __rcu_free_sheaf_prepare (mm/slub.c:2634 mm/slub.c:2940) rcu_free_sheaf (mm/slub.c:5850) rcu_core (kernel/rcu/tree.c:2617 kernel/rcu/tree.c:2869) handle_softirqs (kernel/softirq.c:622) The buggy address belongs to the cache kmalloc-128 of size 128 Queue the old object for kfree_rcu() only after the new one is published, matching ieee80211_set_probe_resp() and ieee80211_set_s1g_short_beacon(). Fixes: 3b1c256eb4ae ("wifi: mac80211: fixes in FILS discovery updates") Reported-by: Weiming Shi Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Xiang Mei Link: https://patch.msgid.link/20260621093532.884188-1-xmei5@asu.edu Signed-off-by: Johannes Berg --- diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c index 3b58af59f7e4..932cf20785bc 100644 --- a/net/mac80211/cfg.c +++ b/net/mac80211/cfg.c @@ -1179,8 +1179,6 @@ ieee80211_set_unsol_bcast_probe_resp(struct ieee80211_sub_if_data *sdata, link_conf->unsol_bcast_probe_resp_interval = params->interval; old = sdata_dereference(link->u.ap.unsol_bcast_probe_resp, sdata); - if (old) - kfree_rcu(old, rcu_head); if (params->tmpl && params->tmpl_len) { new = kzalloc(sizeof(*new) + params->tmpl_len, GFP_KERNEL); @@ -1193,6 +1191,9 @@ ieee80211_set_unsol_bcast_probe_resp(struct ieee80211_sub_if_data *sdata, RCU_INIT_POINTER(link->u.ap.unsol_bcast_probe_resp, NULL); } + if (old) + kfree_rcu(old, rcu_head); + *changed |= BSS_CHANGED_UNSOL_BCAST_PROBE_RESP; return 0; }