This is a note to let you know that I've just added the patch titled
net: sched: extend Qdisc with rcu
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-sched-extend-qdisc-with-rcu.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Fri Dec 10 12:36:13 PM CET 2021
From: Lee Jones <lee.jones@xxxxxxxxxx>
Date: Fri, 10 Dec 2021 10:47:27 +0000
Subject: net: sched: extend Qdisc with rcu
To: lee.jones@xxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx, Vlad Buslov <vladbu@xxxxxxxxxxxx>, Jiri Pirko <jiri@xxxxxxxxxxxx>, "David S . Miller" <davem@xxxxxxxxxxxxx>, syzbot+5f229e48cccc804062c0@xxxxxxxxxxxxxxxxxxxxxxxxx
Message-ID: <20211210104729.582403-3-lee.jones@xxxxxxxxxx>
From: Vlad Buslov <vladbu@xxxxxxxxxxxx>
[ Upstream commit 3a7d0d07a386716b459b00783b11a8211cefcc0f ]
Currently, Qdisc API functions assume that users have rtnl lock taken. To
implement rtnl unlocked classifiers update interface, Qdisc API must be
extended with functions that do not require rtnl lock.
Extend Qdisc structure with rcu. Implement special version of put function
qdisc_put_unlocked() that is called without rtnl lock taken. This function
only takes rtnl lock if Qdisc reference counter reached zero and is
intended to be used as optimization.
Signed-off-by: Vlad Buslov <vladbu@xxxxxxxxxxxx>
Acked-by: Jiri Pirko <jiri@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[Lee: Sent to Stable]
Link: https://syzkaller.appspot.com/bug?id=d7e411c5472dd5da33d8cc921ccadc747743a568
Reported-by: syzbot+5f229e48cccc804062c0@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/rtnetlink.h | 5 +++++
include/net/pkt_sched.h | 1 +
include/net/sch_generic.h | 2 ++
net/sched/sch_api.c | 18 ++++++++++++++++++
net/sched/sch_generic.c | 25 ++++++++++++++++++++++++-
5 files changed, 50 insertions(+), 1 deletion(-)
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -85,6 +85,11 @@ static inline struct netdev_queue *dev_i
return rtnl_dereference(dev->ingress_queue);
}
+static inline struct netdev_queue *dev_ingress_queue_rcu(struct net_device *dev)
+{
+ return rcu_dereference(dev->ingress_queue);
+}
+
struct netdev_queue *dev_ingress_queue_create(struct net_device *dev);
#ifdef CONFIG_NET_INGRESS
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -103,6 +103,7 @@ int qdisc_set_default(const char *id);
void qdisc_hash_add(struct Qdisc *q, bool invisible);
void qdisc_hash_del(struct Qdisc *q);
struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle);
+struct Qdisc *qdisc_lookup_rcu(struct net_device *dev, u32 handle);
struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r,
struct nlattr *tab,
struct netlink_ext_ack *extack);
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -108,6 +108,7 @@ struct Qdisc {
spinlock_t busylock ____cacheline_aligned_in_smp;
spinlock_t seqlock;
+ struct rcu_head rcu;
};
static inline void qdisc_refcount_inc(struct Qdisc *qdisc)
@@ -560,6 +561,7 @@ struct Qdisc *dev_graft_qdisc(struct net
struct Qdisc *qdisc);
void qdisc_reset(struct Qdisc *qdisc);
void qdisc_put(struct Qdisc *qdisc);
+void qdisc_put_unlocked(struct Qdisc *qdisc);
void qdisc_tree_reduce_backlog(struct Qdisc *qdisc, unsigned int n,
unsigned int len);
struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -315,6 +315,24 @@ out:
return q;
}
+struct Qdisc *qdisc_lookup_rcu(struct net_device *dev, u32 handle)
+{
+ struct netdev_queue *nq;
+ struct Qdisc *q;
+
+ if (!handle)
+ return NULL;
+ q = qdisc_match_from_root(dev->qdisc, handle);
+ if (q)
+ goto out;
+
+ nq = dev_ingress_queue_rcu(dev);
+ if (nq)
+ q = qdisc_match_from_root(nq->qdisc_sleeping, handle);
+out:
+ return q;
+}
+
static struct Qdisc *qdisc_leaf(struct Qdisc *p, u32 classid)
{
unsigned long cl;
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -958,6 +958,13 @@ void qdisc_free(struct Qdisc *qdisc)
kfree((char *) qdisc - qdisc->padded);
}
+void qdisc_free_cb(struct rcu_head *head)
+{
+ struct Qdisc *q = container_of(head, struct Qdisc, rcu);
+
+ qdisc_free(q);
+}
+
static void qdisc_destroy(struct Qdisc *qdisc)
{
const struct Qdisc_ops *ops;
@@ -991,7 +998,7 @@ static void qdisc_destroy(struct Qdisc *
kfree_skb_list(skb);
}
- qdisc_free(qdisc);
+ call_rcu(&qdisc->rcu, qdisc_free_cb);
}
void qdisc_put(struct Qdisc *qdisc)
@@ -1004,6 +1011,22 @@ void qdisc_put(struct Qdisc *qdisc)
}
EXPORT_SYMBOL(qdisc_put);
+/* Version of qdisc_put() that is called with rtnl mutex unlocked.
+ * Intended to be used as optimization, this function only takes rtnl lock if
+ * qdisc reference counter reached zero.
+ */
+
+void qdisc_put_unlocked(struct Qdisc *qdisc)
+{
+ if (qdisc->flags & TCQ_F_BUILTIN ||
+ !refcount_dec_and_rtnl_lock(&qdisc->refcnt))
+ return;
+
+ qdisc_destroy(qdisc);
+ rtnl_unlock();
+}
+EXPORT_SYMBOL(qdisc_put_unlocked);
+
/* Attach toplevel qdisc to device queue. */
struct Qdisc *dev_graft_qdisc(struct netdev_queue *dev_queue,
struct Qdisc *qdisc)
Patches currently in stable-queue which might be from lee.jones@xxxxxxxxxx are
queue-4.19/net-core-netlink-add-helper-refcount-dec-and-lock-function.patch
queue-4.19/net-sched-use-qdisc-rcu-api-instead-of-relying-on-rtnl-lock.patch
queue-4.19/net-sched-extend-qdisc-with-rcu.patch
queue-4.19/net-sched-rename-qdisc_destroy-to-qdisc_put.patch
queue-4.19/net-sched-add-helper-function-to-take-reference-to-qdisc.patch
