net: sched: add rcu annotations around qdisc->qdisc_sleeping

syzbot reported a race around qdisc->qdisc_sleeping [1]

It is time we add proper annotations to reads and writes to/from
qdisc->qdisc_sleeping.

[1]
BUG: KCSAN: data-race in dev_graft_qdisc / qdisc_lookup_rcu

read to 0xffff8881286fc618 of 8 bytes by task 6928 on cpu 1:
qdisc_lookup_rcu+0x192/0x2c0 net/sched/sch_api.c:331
__tcf_qdisc_find+0x74/0x3c0 net/sched/cls_api.c:1174
tc_get_tfilter+0x18f/0x990 net/sched/cls_api.c:2547
rtnetlink_rcv_msg+0x7af/0x8c0 net/core/rtnetlink.c:6386
netlink_rcv_skb+0x126/0x220 net/netlink/af_netlink.c:2546
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6413
netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]
netlink_unicast+0x56f/0x640 net/netlink/af_netlink.c:1365
netlink_sendmsg+0x665/0x770 net/netlink/af_netlink.c:1913
sock_sendmsg_nosec net/socket.c:724 [inline]
sock_sendmsg net/socket.c:747 [inline]
____sys_sendmsg+0x375/0x4c0 net/socket.c:2503
___sys_sendmsg net/socket.c:2557 [inline]
__sys_sendmsg+0x1e3/0x270 net/socket.c:2586
__do_sys_sendmsg net/socket.c:2595 [inline]
__se_sys_sendmsg net/socket.c:2593 [inline]
__x64_sys_sendmsg+0x46/0x50 net/socket.c:2593
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

write to 0xffff8881286fc618 of 8 bytes by task 6912 on cpu 0:
dev_graft_qdisc+0x4f/0x80 net/sched/sch_generic.c:1115
qdisc_graft+0x7d0/0xb60 net/sched/sch_api.c:1103
tc_modify_qdisc+0x712/0xf10 net/sched/sch_api.c:1693
rtnetlink_rcv_msg+0x807/0x8c0 net/core/rtnetlink.c:6395
netlink_rcv_skb+0x126/0x220 net/netlink/af_netlink.c:2546
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6413
netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]
netlink_unicast+0x56f/0x640 net/netlink/af_netlink.c:1365
netlink_sendmsg+0x665/0x770 net/netlink/af_netlink.c:1913
sock_sendmsg_nosec net/socket.c:724 [inline]
sock_sendmsg net/socket.c:747 [inline]
____sys_sendmsg+0x375/0x4c0 net/socket.c:2503
___sys_sendmsg net/socket.c:2557 [inline]
__sys_sendmsg+0x1e3/0x270 net/socket.c:2586
__do_sys_sendmsg net/socket.c:2595 [inline]
__se_sys_sendmsg net/socket.c:2593 [inline]
__x64_sys_sendmsg+0x46/0x50 net/socket.c:2593
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 6912 Comm: syz-executor.5 Not tainted 6.4.0-rc3-syzkaller-00190-g0d85b27b0cc6 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/16/2023

Fixes: 3a7d0d07a386 ("net: sched: extend Qdisc with rcu")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Vlad Buslov <vladbu@nvidia.com>
Acked-by: Jamal Hadi Salim<jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 16 insertions, 10 deletions

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 9ea51812b9cf..e4b6452318c0 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -309,7 +309,7 @@ struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle)
 
 	if (dev_ingress_queue(dev))
 		q = qdisc_match_from_root(
-			dev_ingress_queue(dev)->qdisc_sleeping,
+			rtnl_dereference(dev_ingress_queue(dev)->qdisc_sleeping),
 			handle);
 out:
 	return q;
@@ -328,7 +328,8 @@ struct Qdisc *qdisc_lookup_rcu(struct net_device *dev, u32 handle)
 
 	nq = dev_ingress_queue_rcu(dev);
 	if (nq)
-		q = qdisc_match_from_root(nq->qdisc_sleeping, handle);
+		q = qdisc_match_from_root(rcu_dereference(nq->qdisc_sleeping),
+					  handle);
 out:
 	return q;
 }
@@ -634,8 +635,13 @@ EXPORT_SYMBOL(qdisc_watchdog_init);
 void qdisc_watchdog_schedule_range_ns(struct qdisc_watchdog *wd, u64 expires,
 				      u64 delta_ns)
 {
-	if (test_bit(__QDISC_STATE_DEACTIVATED,
-		     &qdisc_root_sleeping(wd->qdisc)->state))
+	bool deactivated;
+
+	rcu_read_lock();
+	deactivated = test_bit(__QDISC_STATE_DEACTIVATED,
+			       &qdisc_root_sleeping(wd->qdisc)->state);
+	rcu_read_unlock();
+	if (deactivated)
 		return;
 
 	if (hrtimer_is_queued(&wd->timer)) {
@@ -1478,7 +1484,7 @@ static int tc_get_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
 				}
 				q = qdisc_leaf(p, clid);
 			} else if (dev_ingress_queue(dev)) {
-				q = dev_ingress_queue(dev)->qdisc_sleeping;
+				q = rtnl_dereference(dev_ingress_queue(dev)->qdisc_sleeping);
 			}
 		} else {
 			q = rtnl_dereference(dev->qdisc);
@@ -1564,7 +1570,7 @@ replay:
 				}
 				q = qdisc_leaf(p, clid);
 			} else if (dev_ingress_queue_create(dev)) {
-				q = dev_ingress_queue(dev)->qdisc_sleeping;
+				q = rtnl_dereference(dev_ingress_queue(dev)->qdisc_sleeping);
 			}
 		} else {
 			q = rtnl_dereference(dev->qdisc);
@@ -1805,8 +1811,8 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
 
 		dev_queue = dev_ingress_queue(dev);
 		if (dev_queue &&
-		    tc_dump_qdisc_root(dev_queue->qdisc_sleeping, skb, cb,
-				       &q_idx, s_q_idx, false,
+		    tc_dump_qdisc_root(rtnl_dereference(dev_queue->qdisc_sleeping),
+				       skb, cb, &q_idx, s_q_idx, false,
 				       tca[TCA_DUMP_INVISIBLE]) < 0)
 			goto done;
 
@@ -2249,8 +2255,8 @@ static int tc_dump_tclass(struct sk_buff *skb, struct netlink_callback *cb)
 
 	dev_queue = dev_ingress_queue(dev);
 	if (dev_queue &&
-	    tc_dump_tclass_root(dev_queue->qdisc_sleeping, skb, tcm, cb,
-				&t, s_t, false) < 0)
+	    tc_dump_tclass_root(rtnl_dereference(dev_queue->qdisc_sleeping),
+				skb, tcm, cb, &t, s_t, false) < 0)
 		goto done;
 
 done: