[PATCH 5.4 011/155] ipv4: fix a RCU-list lock in inet_dump_fib()

Greg Kroah-Hartman
2020-03-31T09:10:49Z

From: Qian Cai <cai@lca.pw>

[ Upstream commit dddeb30bfc43926620f954266fd12c65a7206f07 ]

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 <cai@lca.pw>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/fib_frontend.c | 2 ++
1 file changed, 2 insertions(+)

--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1007,7 +1007,9 @@ static int inet_dump_fib(struct sk_buff
return -ENOENT;
}

+ rcu_read_lock();
err = fib_table_dump(tb, skb, cb, &filter);
+ rcu_read_unlock();
return skb->len ? : err;
}