From: Jiri Pirko <[email protected]>
In case the qdisc_match_from_root function() is called from non-rcu path
with rtnl mutex held, a suspiciout rcu usage warning appears:
[ 241.504354] =============================
[ 241.504358] WARNING: suspicious RCU usage
[ 241.504366] 5.8.0-rc4-custom-01521-g72a7c7d549c3 #32 Not tainted
[ 241.504370] -----------------------------
[ 241.504378] net/sched/sch_api.c:270 RCU-list traversed in non-reader
section!!
[ 241.504382]
other info that might help us debug this:
[ 241.504388]
rcu_scheduler_active = 2, debug_locks = 1
[ 241.504394] 1 lock held by tc/1391:
[ 241.504398] #0: ffffffff85a27850 (rtnl_mutex){+.+.}-{3:3}, at:
rtnetlink_rcv_msg+0x49a/0xbd0
[ 241.504431]
stack backtrace:
[ 241.504440] CPU: 0 PID: 1391 Comm: tc Not tainted
5.8.0-rc4-custom-01521-g72a7c7d549c3 #32
[ 241.504446] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-2.fc32 04/01/2014
[ 241.504453] Call Trace:
[ 241.504465] dump_stack+0x100/0x184
[ 241.504482] lockdep_rcu_suspicious+0x153/0x15d
[ 241.504499] qdisc_match_from_root+0x293/0x350
Fix this by taking the rcu_lock for qdisc_hash iteration.
Reported-by: Ido Schimmel <[email protected]>
Signed-off-by: Jiri Pirko <[email protected]>
---
net/sched/sch_api.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 11ebba60da3b..c7cfd8dc6a77 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -267,10 +267,12 @@ static struct Qdisc *qdisc_match_from_root(struct Qdisc
*root, u32 handle)
root->handle == handle)
return root;
+ rcu_read_lock();
hash_for_each_possible_rcu(qdisc_dev(root)->qdisc_hash, q, hash,
handle) {
if (q->handle == handle)
return q;
}
+ rcu_read_unlock();
return NULL;
}
--
2.21.3
