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net_sched: add __rcu annotation to netdev->qdisc
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commit 5891cd5 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: 470502d ("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>
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@gregkh
Eric Dumazet authored and gregkh committed Feb 23, 2022
1 parent 877a056 commit d9bd9d4
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Showing 5 changed files with 36 additions and 29 deletions.
2 changes: 1 addition & 1 deletion include/linux/netdevice.h
View file
Expand Up @@ -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;

Expand Down
6 changes: 4 additions & 2 deletions net/core/rtnetlink.c
View file
Expand Up @@ -1705,6 +1705,7 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
{
struct ifinfomsg *ifm;
struct nlmsghdr *nlh;
struct Qdisc *qdisc;

ASSERT_RTNL();
nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ifm), flags);
Expand All @@ -1722,6 +1723,7 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
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,
Expand All @@ -1740,8 +1742,8 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
#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) +
Expand Down
6 changes: 3 additions & 3 deletions net/sched/cls_api.c
View file
Expand Up @@ -1045,7 +1045,7 @@ static int __tcf_qdisc_find(struct net *net, struct Qdisc **q,

/* 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));
Expand Down Expand Up @@ -2591,7 +2591,7 @@ static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)

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)
Expand Down Expand Up @@ -2977,7 +2977,7 @@ static int tc_dump_chain(struct sk_buff *skb, struct netlink_callback *cb)

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));
Expand Down
22 changes: 12 additions & 10 deletions net/sched/sch_api.c
View file
Expand Up @@ -301,7 +301,7 @@ struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle)

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;

Expand All @@ -320,7 +320,7 @@ struct Qdisc *qdisc_lookup_rcu(struct net_device *dev, u32 handle)

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;

Expand Down Expand Up @@ -1082,10 +1082,10 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
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);
Expand Down Expand Up @@ -1460,7 +1460,7 @@ static int tc_get_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
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");
Expand Down Expand Up @@ -1549,7 +1549,7 @@ static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
q = dev_ingress_queue(dev)->qdisc_sleeping;
}
} else {
q = dev->qdisc;
q = rtnl_dereference(dev->qdisc);
}

/* It may be default qdisc, ignore it */
Expand Down Expand Up @@ -1771,7 +1771,8 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
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;

Expand Down Expand Up @@ -2047,7 +2048,7 @@ static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n,
} 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.
Expand All @@ -2058,7 +2059,7 @@ static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n,
portid = TC_H_MAKE(qid, portid);
} else {
if (qid == 0)
qid = dev->qdisc->handle;
qid = rtnl_dereference(dev->qdisc)->handle;
}

/* OK. Locate qdisc */
Expand Down Expand Up @@ -2219,7 +2220,8 @@ static int tc_dump_tclass(struct sk_buff *skb, struct netlink_callback *cb)
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);
Expand Down
29 changes: 16 additions & 13 deletions net/sched/sch_generic.c
View file
Expand Up @@ -1088,30 +1088,33 @@ static void attach_default_qdiscs(struct net_device *dev)
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
}

Expand Down Expand Up @@ -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))
Expand Down Expand Up @@ -1306,7 +1309,7 @@ static int qdisc_change_tx_queue_len(struct net_device *dev,
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);
Expand Down Expand Up @@ -1346,7 +1349,7 @@ static void dev_init_scheduler_queue(struct net_device *dev,

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);
Expand Down Expand Up @@ -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));
}
Expand Down

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