From: Xiang Mei Date: Sun, 21 Jun 2026 09:35:32 +0000 (-0700) Subject: wifi: mac80211: fix fils_discovery double free on alloc failure X-Git-Tag: v7.2-rc4~17^2~16^2~36 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=286e52a799fa158bdbd77da1426c4d93f9a6e7ad;p=thirdparty%2Fkernel%2Flinux.git wifi: mac80211: fix fils_discovery double free on alloc failure ieee80211_set_fils_discovery() calls kfree_rcu() on the old template before allocating the replacement. If the kzalloc() then fails, it returns -ENOMEM while link->u.ap.fils_discovery still points at the object already queued for freeing. A later update or AP teardown (ieee80211_stop_ap()) 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 ffff88800c065280 by task swapper/0/0 ... __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-96 of size 96 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/20260621093532.884188-2-xmei5@asu.edu Signed-off-by: Johannes Berg --- diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c index 932cf20785bc..b00191e02a63 100644 --- a/net/mac80211/cfg.c +++ b/net/mac80211/cfg.c @@ -1146,9 +1146,6 @@ static int ieee80211_set_fils_discovery(struct ieee80211_sub_if_data *sdata, fd->max_interval = params->max_interval; old = sdata_dereference(link->u.ap.fils_discovery, sdata); - if (old) - kfree_rcu(old, rcu_head); - if (params->tmpl && params->tmpl_len) { new = kzalloc(sizeof(*new) + params->tmpl_len, GFP_KERNEL); if (!new) @@ -1160,6 +1157,9 @@ static int ieee80211_set_fils_discovery(struct ieee80211_sub_if_data *sdata, RCU_INIT_POINTER(link->u.ap.fils_discovery, NULL); } + if (old) + kfree_rcu(old, rcu_head); + *changed |= BSS_CHANGED_FILS_DISCOVERY; return 0; }