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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: f0ad0860d0 ("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>
This commit is contained in:
Amol Grover 2020-05-14 23:31:03 +05:30 committed by David S. Miller
parent a14fbcd4f1
commit 7013908c2d
1 changed files with 4 additions and 3 deletions
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7
net/ipv4/ipmr.c
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@ -109,9 +109,10 @@ static void mroute_clean_tables(struct mr_table *mrt, int flags);
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())
#define ipmr_for_each_table(mrt, net) \
list_for_each_entry_rcu(mrt, &net->ipv4.mr_tables, list, \
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)