[PATCH net-next 13/15] batman-adv: bla: increase hash generation when purging entries

[Simon Wunderlich <sw@simonwunderlich.de>]

From: Sven Eckelmann <sven@narfation.org>

If batadv_bla_claim_dump() or batadv_bla_backbone_dump() is preempted
during a netlink dump and resumes in the middle of a hash bucket while
batadv_bla_del_backbone_claims() or batadv_bla_purge_backbone_gw()
concurrently removes an entry, the dump offset will be shifted.

Without incrementing the hash generation counter, netlink won't set
NLM_F_DUMP_INTR and the userspace will not be informed about the
inconsistent dump.

Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/bug/linux-83da443f-ce69-4393-a29f-e02b70d1ec96
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
---
 net/batman-adv/bridge_loop_avoidance.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c
index 9be452f667250..ba410dca1c89c 100644
--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -319,6 +319,7 @@ batadv_bla_del_backbone_claims(struct batadv_bla_backbone_gw *backbone_gw)
 				continue;
 
 			hlist_del_rcu(&claim->hash_entry);
+			atomic_inc(&hash->generation);
 			batadv_claim_put(claim);
 		}
 		spin_unlock_bh(list_lock);
@@ -1286,6 +1287,7 @@ static void batadv_bla_purge_backbone_gw(struct batadv_priv *bat_priv, int now)
 				batadv_bla_del_backbone_claims(backbone_gw);
 
 				hlist_del_rcu(&backbone_gw->hash_entry);
+				atomic_inc(&hash->generation);
 				break;
 			}
 			spin_unlock_bh(list_lock);
-- 
2.47.3