netdev - [PATCH net 2/2] netfilter: ipset: fix region locking in hash types

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Message-Id: <20250507221952.86505-3-pablo@netfilter.org>
Date: Thu,  8 May 2025 00:19:52 +0200
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net,
	netdev@...r.kernel.org,
	kuba@...nel.org,
	pabeni@...hat.com,
	edumazet@...gle.com,
	fw@...len.de,
	horms@...nel.org
Subject: [PATCH net 2/2] netfilter: ipset: fix region locking in hash types

From: Jozsef Kadlecsik <kadlec@...filter.org>

Region locking introduced in v5.6-rc4 contained three macros to handle
the region locks: ahash_bucket_start(), ahash_bucket_end() which gave
back the start and end hash bucket values belonging to a given region
lock and ahash_region() which should give back the region lock belonging
to a given hash bucket. The latter was incorrect which can lead to a
race condition between the garbage collector and adding new elements
when a hash type of set is defined with timeouts.

Fixes: f66ee0410b1c ("netfilter: ipset: Fix "INFO: rcu detected stall in hash_xxx" reports")
Reported-by: Kota Toda <kota.toda@...-cybersecurity.com>
Signed-off-by: Jozsef Kadlecsik <kadlec@...filter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/ipset/ip_set_hash_gen.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/ipset/ip_set_hash_gen.h b/net/netfilter/ipset/ip_set_hash_gen.h
index cf3ce72c3de6..5251524b96af 100644
--- a/net/netfilter/ipset/ip_set_hash_gen.h
+++ b/net/netfilter/ipset/ip_set_hash_gen.h
@@ -64,7 +64,7 @@ struct hbucket {
 #define ahash_sizeof_regions(htable_bits)		\
 	(ahash_numof_locks(htable_bits) * sizeof(struct ip_set_region))
 #define ahash_region(n, htable_bits)		\
-	((n) % ahash_numof_locks(htable_bits))
+	((n) / jhash_size(HTABLE_REGION_BITS))
 #define ahash_bucket_start(h,  htable_bits)	\
 	((htable_bits) < HTABLE_REGION_BITS ? 0	\
 		: (h) * jhash_size(HTABLE_REGION_BITS))
-- 
2.30.2