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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id v76sm342432qka.32.2020.03.25.07.32.10 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 25 Mar 2020 07:32:11 -0700 (PDT) From: Qian Cai To: pablo@netfilter.org, kadlec@netfilter.org, fw@strlen.de Cc: davem@davemloft.net, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH] netfilter/nf_tables: silence a RCU-list warning Date: Wed, 25 Mar 2020 10:31:42 -0400 Message-Id: <20200325143142.6955-1-cai@lca.pw> X-Mailer: git-send-email 2.21.0 (Apple Git-122.2) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org It is safe to traverse &net->nft.tables with &net->nft.commit_mutex held using list_for_each_entry_rcu(). Silence the PROVE_RCU_LIST false positive, WARNING: suspicious RCU usage net/netfilter/nf_tables_api.c:523 RCU-list traversed in non-reader section!! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 1 lock held by iptables/1384: #0: ffffffff9745c4a8 (&net->nft.commit_mutex){+.+.}, at: nf_tables_valid_genid+0x25/0x60 [nf_tables] Call Trace: dump_stack+0xa1/0xea lockdep_rcu_suspicious+0x103/0x10d nft_table_lookup.part.0+0x116/0x120 [nf_tables] nf_tables_newtable+0x12c/0x7d0 [nf_tables] nfnetlink_rcv_batch+0x559/0x1190 [nfnetlink] nfnetlink_rcv+0x1da/0x210 [nfnetlink] netlink_unicast+0x306/0x460 netlink_sendmsg+0x44b/0x770 ____sys_sendmsg+0x46b/0x4a0 ___sys_sendmsg+0x138/0x1a0 __sys_sendmsg+0xb6/0x130 __x64_sys_sendmsg+0x48/0x50 do_syscall_64+0x69/0xf4 entry_SYSCALL_64_after_hwframe+0x49/0xb3 Signed-off-by: Qian Cai --- net/netfilter/nf_tables_api.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index 38c680f28f15..e398d1491057 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -520,7 +520,8 @@ static struct nft_table *nft_table_lookup(const struct net *net, if (nla == NULL) return ERR_PTR(-EINVAL); - list_for_each_entry_rcu(table, &net->nft.tables, list) { + list_for_each_entry_rcu(table, &net->nft.tables, list, + lockdep_is_held(&net->nft.commit_mutex)) { if (!nla_strcmp(nla, table->name) && table->family == family && nft_active_genmask(table, genmask)) -- 2.21.0 (Apple Git-122.2)