Re: [PATCH] ipv4: fix a RCU-list bug in inet_dump_fib()
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From: David Ahern <hidden>
Date: 2020-03-19 22:32:22
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On 3/19/20 4:11 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() 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
Fixes: 18a8021a7be3 ("net/ipv4: Plumb support for filtering route dumps")
but you have a problem below ...
quoted hunk ↗ jump to hunk
Signed-off-by: Qian Cai <redacted> --- 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) {
this branch has 2 return points which now have rcu_read_lock; you should have seen this when you tested the change..