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wifi: mac80211: fix fils_discovery double free on alloc failure

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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: 3b1c256eb4 ("wifi: mac80211: fixes in FILS discovery updates")
Reported-by: Weiming Shi <bestswngs@gmail.com>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Xiang Mei <xmei5@asu.edu>
Link: https://patch.msgid.link/20260621093532.884188-2-xmei5@asu.edu
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Xiang Mei 2026-06-21 02:35:32 -07:00 committed by Johannes Berg
parent 1d067abcd3
commit 286e52a799
1 changed files with 3 additions and 3 deletions
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6
net/mac80211/cfg.c
View File

@ -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;
}