[PATCH 5.10 063/121] net_sched: add __rcu annotation to netdev->qdisc

Greg Kroah-Hartman
2022-02-21T09:14:33Z

From: Eric Dumazet <edumazet@google.com>

commit 5891cd5ec46c2c2eb6427cb54d214b149635dd0e upstream.

syzbot found a data-race [1] which lead me to add __rcu
annotations to netdev->qdisc, and proper accessors
to get LOCKDEP support.

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

write to 0xffff888168ad6410 of 8 bytes by task 13559 on cpu 1:
attach_default_qdiscs net/sched/sch_generic.c:1167 [inline]
dev_activate+0x2ed/0x8f0 net/sched/sch_generic.c:1221
__dev_open+0x2e9/0x3a0 net/core/dev.c:1416
__dev_change_flags+0x167/0x3f0 net/core/dev.c:8139
rtnl_configure_link+0xc2/0x150 net/core/rtnetlink.c:3150
__rtnl_newlink net/core/rtnetlink.c:3489 [inline]
rtnl_newlink+0xf4d/0x13e0 net/core/rtnetlink.c:3529
rtnetlink_rcv_msg+0x745/0x7e0 net/core/rtnetlink.c:5594
netlink_rcv_skb+0x14e/0x250 net/netlink/af_netlink.c:2494
rtnetlink_rcv+0x18/0x20 net/core/rtnetlink.c:5612
netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
netlink_unicast+0x602/0x6d0 net/netlink/af_netlink.c:1343
netlink_sendmsg+0x728/0x850 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:705 [inline]
sock_sendmsg net/socket.c:725 [inline]
____sys_sendmsg+0x39a/0x510 net/socket.c:2413
___sys_sendmsg net/socket.c:2467 [inline]
__sys_sendmsg+0x195/0x230 net/socket.c:2496
__do_sys_sendmsg net/socket.c:2505 [inline]
__se_sys_sendmsg net/socket.c:2503 [inline]
__x64_sys_sendmsg+0x42/0x50 net/socket.c:2503
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888168ad6410 of 8 bytes by task 13560 on cpu 0:
qdisc_lookup_rcu+0x30/0x2e0 net/sched/sch_api.c:323
__tcf_qdisc_find+0x74/0x3a0 net/sched/cls_api.c:1050
tc_del_tfilter+0x1c7/0x1350 net/sched/cls_api.c:2211
rtnetlink_rcv_msg+0x5ba/0x7e0 net/core/rtnetlink.c:5585
netlink_rcv_skb+0x14e/0x250 net/netlink/af_netlink.c:2494
rtnetlink_rcv+0x18/0x20 net/core/rtnetlink.c:5612
netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
netlink_unicast+0x602/0x6d0 net/netlink/af_netlink.c:1343
netlink_sendmsg+0x728/0x850 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:705 [inline]
sock_sendmsg net/socket.c:725 [inline]
____sys_sendmsg+0x39a/0x510 net/socket.c:2413
___sys_sendmsg net/socket.c:2467 [inline]
__sys_sendmsg+0x195/0x230 net/socket.c:2496
__do_sys_sendmsg net/socket.c:2505 [inline]
__se_sys_sendmsg net/socket.c:2503 [inline]
__x64_sys_sendmsg+0x42/0x50 net/socket.c:2503
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0xffffffff85dee080 -> 0xffff88815d96ec00

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 13560 Comm: syz-executor.2 Not tainted 5.17.0-rc3-syzkaller-00116-gf1baf68e1383-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

Fixes: 470502de5bdb ("net: sched: unlock rules update API")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Vlad Buslov <vladbu@mellanox.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/netdevice.h | 2 +-
net/core/rtnetlink.c | 6 ++++--
net/sched/cls_api.c | 6 +++---
net/sched/sch_api.c | 22 ++++++++++++----------
net/sched/sch_generic.c | 29 ++++++++++++++++-------------
5 files changed, 36 insertions(+), 29 deletions(-)

--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2061,7 +2061,7 @@ struct net_device {
struct netdev_queue *_tx ____cacheline_aligned_in_smp;
unsigned int num_tx_queues;
unsigned int real_num_tx_queues;
- struct Qdisc *qdisc;
+ struct Qdisc __rcu *qdisc;
unsigned int tx_queue_len;
spinlock_t tx_global_lock;

--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1705,6 +1705,7 @@ static int rtnl_fill_ifinfo(struct sk_bu
{
struct ifinfomsg *ifm;
struct nlmsghdr *nlh;
+ struct Qdisc *qdisc;

ASSERT_RTNL();
nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ifm), flags);
@@ -1722,6 +1723,7 @@ static int rtnl_fill_ifinfo(struct sk_bu
if (tgt_netnsid >= 0 && nla_put_s32(skb, IFLA_TARGET_NETNSID, tgt_netnsid))
goto nla_put_failure;

+ qdisc = rtnl_dereference(dev->qdisc);
if (nla_put_string(skb, IFLA_IFNAME, dev->name) ||
nla_put_u32(skb, IFLA_TXQLEN, dev->tx_queue_len) ||
nla_put_u8(skb, IFLA_OPERSTATE,
@@ -1740,8 +1742,8 @@ static int rtnl_fill_ifinfo(struct sk_bu
#endif
put_master_ifindex(skb, dev) ||
nla_put_u8(skb, IFLA_CARRIER, netif_carrier_ok(dev)) ||
- (dev->qdisc &&
- nla_put_string(skb, IFLA_QDISC, dev->qdisc->ops->id)) ||
+ (qdisc &&
+ nla_put_string(skb, IFLA_QDISC, qdisc->ops->id)) ||
nla_put_ifalias(skb, dev) ||
nla_put_u32(skb, IFLA_CARRIER_CHANGES,
atomic_read(&dev->carrier_up_count) +
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -1045,7 +1045,7 @@ static int __tcf_qdisc_find(struct net *

/* Find qdisc */
if (!*parent) {
- *q = dev->qdisc;
+ *q = rcu_dereference(dev->qdisc);
*parent = (*q)->handle;
} else {
*q = qdisc_lookup_rcu(dev, TC_H_MAJ(*parent));
@@ -2591,7 +2591,7 @@ static int tc_dump_tfilter(struct sk_buf

parent = tcm->tcm_parent;
if (!parent)
- q = dev->qdisc;
+ q = rtnl_dereference(dev->qdisc);
else
q = qdisc_lookup(dev, TC_H_MAJ(tcm->tcm_parent));
if (!q)
@@ -2977,7 +2977,7 @@ static int tc_dump_chain(struct sk_buff

parent = tcm->tcm_parent;
if (!parent) {
- q = dev->qdisc;
+ q = rtnl_dereference(dev->qdisc);
parent = q->handle;
} else {
q = qdisc_lookup(dev, TC_H_MAJ(tcm->tcm_parent));
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -301,7 +301,7 @@ struct Qdisc *qdisc_lookup(struct net_de

if (!handle)
return NULL;
- q = qdisc_match_from_root(dev->qdisc, handle);
+ q = qdisc_match_from_root(rtnl_dereference(dev->qdisc), handle);
if (q)
goto out;

@@ -320,7 +320,7 @@ struct Qdisc *qdisc_lookup_rcu(struct ne

if (!handle)
return NULL;
- q = qdisc_match_from_root(dev->qdisc, handle);
+ q = qdisc_match_from_root(rcu_dereference(dev->qdisc), handle);
if (q)
goto out;

@@ -1082,10 +1082,10 @@ static int qdisc_graft(struct net_device
skip:
if (!ingress) {
notify_and_destroy(net, skb, n, classid,
- dev->qdisc, new);
+ rtnl_dereference(dev->qdisc), new);
if (new && !new->ops->attach)
qdisc_refcount_inc(new);
- dev->qdisc = new ? : &noop_qdisc;
+ rcu_assign_pointer(dev->qdisc, new ? : &noop_qdisc);

if (new && new->ops->attach)
new->ops->attach(new);
@@ -1460,7 +1460,7 @@ static int tc_get_qdisc(struct sk_buff *
q = dev_ingress_queue(dev)->qdisc_sleeping;
}
} else {
- q = dev->qdisc;
+ q = rtnl_dereference(dev->qdisc);
}
if (!q) {
NL_SET_ERR_MSG(extack, "Cannot find specified qdisc on specified device");
@@ -1549,7 +1549,7 @@ replay:
q = dev_ingress_queue(dev)->qdisc_sleeping;
}
} else {
- q = dev->qdisc;
+ q = rtnl_dereference(dev->qdisc);
}

/* It may be default qdisc, ignore it */
@@ -1771,7 +1771,8 @@ static int tc_dump_qdisc(struct sk_buff
s_q_idx = 0;
q_idx = 0;

- if (tc_dump_qdisc_root(dev->qdisc, skb, cb, &q_idx, s_q_idx,
+ if (tc_dump_qdisc_root(rtnl_dereference(dev->qdisc),
+ skb, cb, &q_idx, s_q_idx,
true, tca[TCA_DUMP_INVISIBLE]) < 0)
goto done;

@@ -2047,7 +2048,7 @@ static int tc_ctl_tclass(struct sk_buff
} else if (qid1) {
qid = qid1;
} else if (qid == 0)
- qid = dev->qdisc->handle;
+ qid = rtnl_dereference(dev->qdisc)->handle;

/* Now qid is genuine qdisc handle consistent
* both with parent and child.
@@ -2058,7 +2059,7 @@ static int tc_ctl_tclass(struct sk_buff
portid = TC_H_MAKE(qid, portid);
} else {
if (qid == 0)
- qid = dev->qdisc->handle;
+ qid = rtnl_dereference(dev->qdisc)->handle;
}

/* OK. Locate qdisc */
@@ -2219,7 +2220,8 @@ static int tc_dump_tclass(struct sk_buff
s_t = cb->args[0];
t = 0;

- if (tc_dump_tclass_root(dev->qdisc, skb, tcm, cb, &t, s_t, true) < 0)
+ if (tc_dump_tclass_root(rtnl_dereference(dev->qdisc),
+ skb, tcm, cb, &t, s_t, true) < 0)
goto done;

dev_queue = dev_ingress_queue(dev);
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -1088,30 +1088,33 @@ static void attach_default_qdiscs(struct
if (!netif_is_multiqueue(dev) ||
dev->priv_flags & IFF_NO_QUEUE) {
netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
- dev->qdisc = txq->qdisc_sleeping;
- qdisc_refcount_inc(dev->qdisc);
+ qdisc = txq->qdisc_sleeping;
+ rcu_assign_pointer(dev->qdisc, qdisc);
+ qdisc_refcount_inc(qdisc);
} else {
qdisc = qdisc_create_dflt(txq, &mq_qdisc_ops, TC_H_ROOT, NULL);
if (qdisc) {
- dev->qdisc = qdisc;
+ rcu_assign_pointer(dev->qdisc, qdisc);
qdisc->ops->attach(qdisc);
}
}
+ qdisc = rtnl_dereference(dev->qdisc);

/* Detect default qdisc setup/init failed and fallback to "noqueue" */
- if (dev->qdisc == &noop_qdisc) {
+ if (qdisc == &noop_qdisc) {
netdev_warn(dev, "default qdisc (%s) fail, fallback to %s\n",
default_qdisc_ops->id, noqueue_qdisc_ops.id);
dev->priv_flags |= IFF_NO_QUEUE;
netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
- dev->qdisc = txq->qdisc_sleeping;
- qdisc_refcount_inc(dev->qdisc);
+ qdisc = txq->qdisc_sleeping;
+ rcu_assign_pointer(dev->qdisc, qdisc);
+ qdisc_refcount_inc(qdisc);
dev->priv_flags ^= IFF_NO_QUEUE;
}

#ifdef CONFIG_NET_SCHED
- if (dev->qdisc != &noop_qdisc)
- qdisc_hash_add(dev->qdisc, false);
+ if (qdisc != &noop_qdisc)
+ qdisc_hash_add(qdisc, false);
#endif
}

@@ -1141,7 +1144,7 @@ void dev_activate(struct net_device *dev
* and noqueue_qdisc for virtual interfaces
*/

- if (dev->qdisc == &noop_qdisc)
+ if (rtnl_dereference(dev->qdisc) == &noop_qdisc)
attach_default_qdiscs(dev);

if (!netif_carrier_ok(dev))
@@ -1306,7 +1309,7 @@ static int qdisc_change_tx_queue_len(str
void dev_qdisc_change_real_num_tx(struct net_device *dev,
unsigned int new_real_tx)
{
- struct Qdisc *qdisc = dev->qdisc;
+ struct Qdisc *qdisc = rtnl_dereference(dev->qdisc);

if (qdisc->ops->change_real_num_tx)
qdisc->ops->change_real_num_tx(qdisc, new_real_tx);
@@ -1346,7 +1349,7 @@ static void dev_init_scheduler_queue(str

void dev_init_scheduler(struct net_device *dev)
{
- dev->qdisc = &noop_qdisc;
+ rcu_assign_pointer(dev->qdisc, &noop_qdisc);
netdev_for_each_tx_queue(dev, dev_init_scheduler_queue, &noop_qdisc);
if (dev_ingress_queue(dev))
dev_init_scheduler_queue(dev, dev_ingress_queue(dev), &noop_qdisc);
@@ -1374,8 +1377,8 @@ void dev_shutdown(struct net_device *dev
netdev_for_each_tx_queue(dev, shutdown_scheduler_queue, &noop_qdisc);
if (dev_ingress_queue(dev))
shutdown_scheduler_queue(dev, dev_ingress_queue(dev), &noop_qdisc);
- qdisc_put(dev->qdisc);
- dev->qdisc = &noop_qdisc;
+ qdisc_put(rtnl_dereference(dev->qdisc));
+ rcu_assign_pointer(dev->qdisc, &noop_qdisc);

WARN_ON(timer_pending(&dev->watchdog_timer));
}