netdev - [PATCH net 1/7] netfilter: nft_set_bitmap: fix lockdep splat due to missing annotation

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Message-ID: <20250910190308.13356-2-fw@strlen.de>
Date: Wed, 10 Sep 2025 21:03:02 +0200
From: Florian Westphal <fw@...len.de>
To: <netdev@...r.kernel.org>
Cc: Paolo Abeni <pabeni@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	<netfilter-devel@...r.kernel.org>,
	pablo@...filter.org
Subject: [PATCH net 1/7] netfilter: nft_set_bitmap: fix lockdep splat due to missing annotation

Running new 'set_flush_add_atomic_bitmap' test case for nftables.git
with CONFIG_PROVE_RCU_LIST=y yields:

net/netfilter/nft_set_bitmap.c:231 RCU-list traversed in non-reader section!!
rcu_scheduler_active = 2, debug_locks = 1
1 lock held by nft/4008:
 #0: ffff888147f79cd8 (&nft_net->commit_mutex){+.+.}-{4:4}, at: nf_tables_valid_genid+0x2f/0xd0

 lockdep_rcu_suspicious+0x116/0x160
 nft_bitmap_walk+0x22d/0x240
 nf_tables_delsetelem+0x1010/0x1a00
 ..

This is a false positive, the list cannot be altered while the
transaction mutex is held, so pass the relevant argument to the iterator.

Fixes tag intentionally wrong; no point in picking this up if earlier
false-positive-fixups were not applied.

Fixes: 28b7a6b84c0a ("netfilter: nf_tables: avoid false-positive lockdep splats in set walker")
Signed-off-by: Florian Westphal <fw@...len.de>
---
 net/netfilter/nft_set_bitmap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nft_set_bitmap.c b/net/netfilter/nft_set_bitmap.c
index c24c922f895d..8d3f040a904a 100644
--- a/net/netfilter/nft_set_bitmap.c
+++ b/net/netfilter/nft_set_bitmap.c
@@ -226,7 +226,8 @@ static void nft_bitmap_walk(const struct nft_ctx *ctx,
 	const struct nft_bitmap *priv = nft_set_priv(set);
 	struct nft_bitmap_elem *be;
 
-	list_for_each_entry_rcu(be, &priv->list, head) {
+	list_for_each_entry_rcu(be, &priv->list, head,
+				lockdep_is_held(&nft_pernet(ctx->net)->commit_mutex)) {
 		if (iter->count < iter->skip)
 			goto cont;
 
-- 
2.49.1