From 0459430add32ea41f3e2ef9351610e6d33627a6b Mon Sep 17 00:00:00 2001 From: Sven Eckelmann Date: Sun, 10 May 2026 11:43:20 +0200 Subject: [PATCH] batman-adv: bla: fix report_work leak on backbone_gw purge batadv_bla_purge_backbone_gw() removes stale backbone gateway entries, but fails to properly handle their associated report_work: - If report_work is running, the purge must wait for it to finish before freeing the backbone_gw, otherwise the worker may access freed memory (e.g. bat_priv). - If report_work is pending, the purge must cancel it and release the reference held for that pending work item. The previous implementation called hlist_for_each_entry_safe() inside a spin_lock_bh() section, but cancel_work_sync() may sleep and therefore cannot be called from within a spinlock-protected region. Restructure the loop to handle one entry per spinlock critical section: acquire the lock, find the next entry to purge, remove it from the hash list, then release the lock before calling cancel_work_sync() and dropping the hash_entry reference. Repeat until no more entries require purging. Cc: stable@kernel.org Fixes: 23721387c409 ("batman-adv: add basic bridge loop avoidance code") Reviewed-by: Simon Wunderlich Signed-off-by: Sven Eckelmann --- net/batman-adv/bridge_loop_avoidance.c | 54 +++++++++++++++++--------- 1 file changed, 35 insertions(+), 19 deletions(-) diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c index cec11f1251d6..df1dfdf4a1a1 100644 --- a/net/batman-adv/bridge_loop_avoidance.c +++ b/net/batman-adv/bridge_loop_avoidance.c @@ -1224,6 +1224,7 @@ static void batadv_bla_purge_backbone_gw(struct batadv_priv *bat_priv, int now) struct hlist_head *head; struct batadv_hashtable *hash; spinlock_t *list_lock; /* protects write access to the hash lists */ + bool purged; int i; hash = bat_priv->bla.backbone_hash; @@ -1234,30 +1235,45 @@ static void batadv_bla_purge_backbone_gw(struct batadv_priv *bat_priv, int now) head = &hash->table[i]; list_lock = &hash->list_locks[i]; - spin_lock_bh(list_lock); - hlist_for_each_entry_safe(backbone_gw, node_tmp, - head, hash_entry) { - if (now) - goto purge_now; - if (!batadv_has_timed_out(backbone_gw->lasttime, - BATADV_BLA_BACKBONE_TIMEOUT)) - continue; + do { + purged = false; - batadv_dbg(BATADV_DBG_BLA, backbone_gw->bat_priv, - "%s(): backbone gw %pM timed out\n", - __func__, backbone_gw->orig); + spin_lock_bh(list_lock); + hlist_for_each_entry_safe(backbone_gw, node_tmp, + head, hash_entry) { + if (now) + goto purge_now; + if (!batadv_has_timed_out(backbone_gw->lasttime, + BATADV_BLA_BACKBONE_TIMEOUT)) + continue; + + batadv_dbg(BATADV_DBG_BLA, backbone_gw->bat_priv, + "%s(): backbone gw %pM timed out\n", + __func__, backbone_gw->orig); purge_now: - /* don't wait for the pending request anymore */ - if (atomic_read(&backbone_gw->request_sent)) - atomic_dec(&bat_priv->bla.num_requests); + purged = true; - batadv_bla_del_backbone_claims(backbone_gw); + /* don't wait for the pending request anymore */ + if (atomic_read(&backbone_gw->request_sent)) + atomic_dec(&bat_priv->bla.num_requests); - hlist_del_rcu(&backbone_gw->hash_entry); - batadv_backbone_gw_put(backbone_gw); - } - spin_unlock_bh(list_lock); + batadv_bla_del_backbone_claims(backbone_gw); + + hlist_del_rcu(&backbone_gw->hash_entry); + break; + } + spin_unlock_bh(list_lock); + + if (purged) { + /* reference for pending report_work */ + if (cancel_work_sync(&backbone_gw->report_work)) + batadv_backbone_gw_put(backbone_gw); + + /* reference for hash_entry */ + batadv_backbone_gw_put(backbone_gw); + } + } while (purged); } }