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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id m10sm2635693qte.71.2020.03.19.15.11.47 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 19 Mar 2020 15:11:48 -0700 (PDT) From: Qian Cai To: davem@davemloft.net Cc: alexander.h.duyck@linux.intel.com, kuznet@ms2.inr.ac.ru, kuba@kernel.org, yoshfuji@linux-ipv6.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH] ipv4: fix a RCU-list bug in inet_dump_fib() Date: Thu, 19 Mar 2020 18:11:41 -0400 Message-Id: <20200319221141.8814-1-cai@lca.pw> X-Mailer: git-send-email 2.21.0 (Apple Git-122.2) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is a place, inet_dump_fib() fib_table_dump fn_trie_dump_leaf() hlist_for_each_entry_rcu() without rcu_read_lock() triggers a warning, WARNING: suspicious RCU usage ----------------------------- net/ipv4/fib_trie.c:2216 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 ip/1923: #0: ffffffff8ce76e40 (rtnl_mutex){+.+.}, at: netlink_dump+0xd6/0x840 Call Trace: dump_stack+0xa1/0xea lockdep_rcu_suspicious+0x103/0x10d fn_trie_dump_leaf+0x581/0x590 fib_table_dump+0x15f/0x220 inet_dump_fib+0x4ad/0x5d0 netlink_dump+0x350/0x840 __netlink_dump_start+0x315/0x3e0 rtnetlink_rcv_msg+0x4d1/0x720 netlink_rcv_skb+0xf0/0x220 rtnetlink_rcv+0x15/0x20 netlink_unicast+0x306/0x460 netlink_sendmsg+0x44b/0x770 __sys_sendto+0x259/0x270 __x64_sys_sendto+0x80/0xa0 do_syscall_64+0x69/0xf4 entry_SYSCALL_64_after_hwframe+0x49/0xb3 Signed-off-by: Qian Cai --- net/ipv4/fib_frontend.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c index 577db1d50a24..5e441282d647 100644 --- a/net/ipv4/fib_frontend.c +++ b/net/ipv4/fib_frontend.c @@ -987,6 +987,8 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb) if (filter.flags & RTM_F_PREFIX) return skb->len; + rcu_read_lock(); + if (filter.table_id) { tb = fib_get_table(net, filter.table_id); if (!tb) { @@ -1004,8 +1006,6 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb) s_h = cb->args[0]; s_e = cb->args[1]; - rcu_read_lock(); - for (h = s_h; h < FIB_TABLE_HASHSZ; h++, s_e = 0) { e = 0; head = &net->ipv4.fib_table_hash[h]; -- 2.21.0 (Apple Git-122.2)