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([2601:282:803:7700:e9f2:4948:e013:782b]) by smtp.googlemail.com with ESMTPSA id gv7sm5220217pjb.16.2020.03.20.08.23.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 20 Mar 2020 08:23:59 -0700 (PDT) Subject: Re: [PATCH v2] ipv4: fix a RCU-list lock in inet_dump_fib() To: Qian Cai , 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 References: <20200320025421.9216-1-cai@lca.pw> From: David Ahern Message-ID: Date: Fri, 20 Mar 2020 09:23:58 -0600 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200320025421.9216-1-cai@lca.pw> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/19/20 8:54 PM, Qian Cai wrote: > There is a place, > > inet_dump_fib() > fib_table_dump > fn_trie_dump_leaf() > hlist_for_each_entry_rcu() > > without rcu_read_lock() will trigger 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 > > Fixes: 18a8021a7be3 ("net/ipv4: Plumb support for filtering route dumps") > Signed-off-by: Qian Cai > --- > > v2: Call rcu_read_unlock() before returning. > Add a "Fixes" tag per David. > > net/ipv4/fib_frontend.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c > index 577db1d50a24..213be9c050ad 100644 > --- a/net/ipv4/fib_frontend.c > +++ b/net/ipv4/fib_frontend.c > @@ -997,7 +997,9 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb) > return -ENOENT; > } > > + rcu_read_lock(); > err = fib_table_dump(tb, skb, cb, &filter); > + rcu_read_unlock(); > return skb->len ? : err; > } > > Reviewed-by: David Ahern