Commit 7013908c authored May 14, 2020 by Amol Grover Committed by David S. Miller May 14, 2020

ipmr: Add lockdep expression to ipmr_for_each_table macro



During the initialization process, ipmr_new_table() is called
to create new tables which in turn calls ipmr_get_table() which
traverses net->ipv4.mr_tables without holding the writer lock.
However, this is safe to do so as no tables exist at this time.
Hence add a suitable lockdep expression to silence the following
false-positive warning:

=============================
WARNING: suspicious RCU usage
5.7.0-rc3-next-20200428-syzkaller #0 Not tainted
-----------------------------
net/ipv4/ipmr.c:136 RCU-list traversed in non-reader section!!

ipmr_get_table+0x130/0x160 net/ipv4/ipmr.c:136
ipmr_new_table net/ipv4/ipmr.c:403 [inline]
ipmr_rules_init net/ipv4/ipmr.c:248 [inline]
ipmr_net_init+0x133/0x430 net/ipv4/ipmr.c:3089

Fixes: f0ad0860 ("ipv4: ipmr: support multiple tables")
Reported-by:  <syzbot+1519f497f2f9f08183c6@syzkaller.appspotmail.com>
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Amol Grover <frextrite@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent a14fbcd4

net/ipv4/ipmr.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -111,7 +111,8 @@ static void ipmr_expire_process(struct timer_list *t);
		#ifdef CONFIG_IP_MROUTE_MULTIPLE_TABLES
		#define ipmr_for_each_table(mrt, net) \
		list_for_each_entry_rcu(mrt, &net->ipv4.mr_tables, list, \
		lockdep_rtnl_is_held())
		lockdep_rtnl_is_held() \|\| \
		list_empty(&net->ipv4.mr_tables))

		static struct mr_table ipmr_mr_table_iter(struct net net,
		struct mr_table *mrt)

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