Netdev Archive on lore.kernel.org
 help / color / Atom feed
* [PATCH bpf-next v5 0/2] net: xdp: XSKMAP improvements
@ 2019-08-15  9:30 Björn Töpel
  2019-08-15  9:30 ` [PATCH bpf-next v5 1/2] xsk: remove AF_XDP socket from map when the socket is released Björn Töpel
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: Björn Töpel @ 2019-08-15  9:30 UTC (permalink / raw)
  To: ast, daniel, netdev
  Cc: Björn Töpel, magnus.karlsson, jonathan.lemon,
	bjorn.topel, bruce.richardson, songliubraving, bpf

This series (v5 and counting) add two improvements for the XSKMAP,
used by AF_XDP sockets.

1. Automatic cleanup when an AF_XDP socket goes out of scope/is
   released. Instead of require that the user manually clears the
   "released" state socket from the map, this is done
   automatically. Each socket tracks which maps it resides in, and
   remove itself from those maps at relase. A notable implementation
   change, is that the sockets references the map, instead of the map
   referencing the sockets. Which implies that when the XSKMAP is
   freed, it is by definition cleared of sockets.

2. The XSKMAP did not honor the BPF_EXIST/BPF_NOEXIST flag on insert,
   which this patch addresses.


Thanks,
Björn

v1->v2: Fixed deadlock and broken cleanup. (Daniel)
v2->v3: Rebased onto bpf-next
v3->v4: {READ, WRITE}_ONCE consistency. (Daniel)
        Socket release/map update race. (Daniel)
v4->v5: Avoid use-after-free on XSKMAP self-assignment [1]. (Daniel)
        Removed redundant assignment in xsk_map_update_elem().
        Variable name consistency; Use map_entry everywhere.

[1] https://lore.kernel.org/bpf/20190802081154.30962-1-bjorn.topel@gmail.com/T/#mc68439e97bc07fa301dad9fc4850ed5aa392f385

Björn Töpel (2):
  xsk: remove AF_XDP socket from map when the socket is released
  xsk: support BPF_EXIST and BPF_NOEXIST flags in XSKMAP

 include/net/xdp_sock.h |  18 ++++++
 kernel/bpf/xskmap.c    | 133 ++++++++++++++++++++++++++++++++++-------
 net/xdp/xsk.c          |  50 ++++++++++++++++
 3 files changed, 179 insertions(+), 22 deletions(-)

-- 
2.20.1


^ permalink raw reply	[flat|nested] 4+ messages in thread

* [PATCH bpf-next v5 1/2] xsk: remove AF_XDP socket from map when the socket is released
  2019-08-15  9:30 [PATCH bpf-next v5 0/2] net: xdp: XSKMAP improvements Björn Töpel
@ 2019-08-15  9:30 ` Björn Töpel
  2019-08-15  9:30 ` [PATCH bpf-next v5 2/2] xsk: support BPF_EXIST and BPF_NOEXIST flags in XSKMAP Björn Töpel
  2019-08-17 21:28 ` [PATCH bpf-next v5 0/2] net: xdp: XSKMAP improvements Daniel Borkmann
  2 siblings, 0 replies; 4+ messages in thread
From: Björn Töpel @ 2019-08-15  9:30 UTC (permalink / raw)
  To: ast, daniel, netdev
  Cc: Björn Töpel, magnus.karlsson, jonathan.lemon,
	bruce.richardson, songliubraving, bpf

From: Björn Töpel <bjorn.topel@intel.com>

When an AF_XDP socket is released/closed the XSKMAP still holds a
reference to the socket in a "released" state. The socket will still
use the netdev queue resource, and block newly created sockets from
attaching to that queue, but no user application can access the
fill/complete/rx/tx queues. This results in that all applications need
to explicitly clear the map entry from the old "zombie state"
socket. This should be done automatically.

In this patch, the sockets tracks, and have a reference to, which maps
it resides in. When the socket is released, it will remove itself from
all maps.

Suggested-by: Bruce Richardson <bruce.richardson@intel.com>
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
---
 include/net/xdp_sock.h |  18 ++++++
 kernel/bpf/xskmap.c    | 125 ++++++++++++++++++++++++++++++++++-------
 net/xdp/xsk.c          |  50 +++++++++++++++++
 3 files changed, 173 insertions(+), 20 deletions(-)

diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index 69796d264f06..066e3ae446a8 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h
@@ -50,6 +50,16 @@ struct xdp_umem {
 	struct list_head xsk_list;
 };
 
+/* Nodes are linked in the struct xdp_sock map_list field, and used to
+ * track which maps a certain socket reside in.
+ */
+struct xsk_map;
+struct xsk_map_node {
+	struct list_head node;
+	struct xsk_map *map;
+	struct xdp_sock **map_entry;
+};
+
 struct xdp_sock {
 	/* struct sock must be the first member of struct xdp_sock */
 	struct sock sk;
@@ -75,6 +85,9 @@ struct xdp_sock {
 	/* Protects generic receive. */
 	spinlock_t rx_lock;
 	u64 rx_dropped;
+	struct list_head map_list;
+	/* Protects map_list */
+	spinlock_t map_list_lock;
 };
 
 struct xdp_buff;
@@ -96,6 +109,11 @@ struct xdp_umem_fq_reuse *xsk_reuseq_swap(struct xdp_umem *umem,
 void xsk_reuseq_free(struct xdp_umem_fq_reuse *rq);
 struct xdp_umem *xdp_get_umem_from_qid(struct net_device *dev, u16 queue_id);
 
+void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,
+			     struct xdp_sock **map_entry);
+int xsk_map_inc(struct xsk_map *map);
+void xsk_map_put(struct xsk_map *map);
+
 static inline char *xdp_umem_get_data(struct xdp_umem *umem, u64 addr)
 {
 	return umem->pages[addr >> PAGE_SHIFT].addr + (addr & (PAGE_SIZE - 1));
diff --git a/kernel/bpf/xskmap.c b/kernel/bpf/xskmap.c
index 9bb96ace9fa1..16031d489173 100644
--- a/kernel/bpf/xskmap.c
+++ b/kernel/bpf/xskmap.c
@@ -13,8 +13,71 @@ struct xsk_map {
 	struct bpf_map map;
 	struct xdp_sock **xsk_map;
 	struct list_head __percpu *flush_list;
+	spinlock_t lock; /* Synchronize map updates */
 };
 
+int xsk_map_inc(struct xsk_map *map)
+{
+	struct bpf_map *m = &map->map;
+
+	m = bpf_map_inc(m, false);
+	return IS_ERR(m) ? PTR_ERR(m) : 0;
+}
+
+void xsk_map_put(struct xsk_map *map)
+{
+	bpf_map_put(&map->map);
+}
+
+static struct xsk_map_node *xsk_map_node_alloc(struct xsk_map *map,
+					       struct xdp_sock **map_entry)
+{
+	struct xsk_map_node *node;
+	int err;
+
+	node = kzalloc(sizeof(*node), GFP_ATOMIC | __GFP_NOWARN);
+	if (!node)
+		return NULL;
+
+	err = xsk_map_inc(map);
+	if (err) {
+		kfree(node);
+		return ERR_PTR(err);
+	}
+
+	node->map = map;
+	node->map_entry = map_entry;
+	return node;
+}
+
+static void xsk_map_node_free(struct xsk_map_node *node)
+{
+	xsk_map_put(node->map);
+	kfree(node);
+}
+
+static void xsk_map_sock_add(struct xdp_sock *xs, struct xsk_map_node *node)
+{
+	spin_lock_bh(&xs->map_list_lock);
+	list_add_tail(&node->node, &xs->map_list);
+	spin_unlock_bh(&xs->map_list_lock);
+}
+
+static void xsk_map_sock_delete(struct xdp_sock *xs,
+				struct xdp_sock **map_entry)
+{
+	struct xsk_map_node *n, *tmp;
+
+	spin_lock_bh(&xs->map_list_lock);
+	list_for_each_entry_safe(n, tmp, &xs->map_list, node) {
+		if (map_entry == n->map_entry) {
+			list_del(&n->node);
+			xsk_map_node_free(n);
+		}
+	}
+	spin_unlock_bh(&xs->map_list_lock);
+}
+
 static struct bpf_map *xsk_map_alloc(union bpf_attr *attr)
 {
 	struct xsk_map *m;
@@ -34,6 +97,7 @@ static struct bpf_map *xsk_map_alloc(union bpf_attr *attr)
 		return ERR_PTR(-ENOMEM);
 
 	bpf_map_init_from_attr(&m->map, attr);
+	spin_lock_init(&m->lock);
 
 	cost = (u64)m->map.max_entries * sizeof(struct xdp_sock *);
 	cost += sizeof(struct list_head) * num_possible_cpus();
@@ -71,21 +135,9 @@ static struct bpf_map *xsk_map_alloc(union bpf_attr *attr)
 static void xsk_map_free(struct bpf_map *map)
 {
 	struct xsk_map *m = container_of(map, struct xsk_map, map);
-	int i;
 
 	bpf_clear_redirect_map(map);
 	synchronize_net();
-
-	for (i = 0; i < map->max_entries; i++) {
-		struct xdp_sock *xs;
-
-		xs = m->xsk_map[i];
-		if (!xs)
-			continue;
-
-		sock_put((struct sock *)xs);
-	}
-
 	free_percpu(m->flush_list);
 	bpf_map_area_free(m->xsk_map);
 	kfree(m);
@@ -164,8 +216,9 @@ static int xsk_map_update_elem(struct bpf_map *map, void *key, void *value,
 			       u64 map_flags)
 {
 	struct xsk_map *m = container_of(map, struct xsk_map, map);
+	struct xdp_sock *xs, *old_xs, **map_entry;
 	u32 i = *(u32 *)key, fd = *(u32 *)value;
-	struct xdp_sock *xs, *old_xs;
+	struct xsk_map_node *node;
 	struct socket *sock;
 	int err;
 
@@ -192,32 +245,64 @@ static int xsk_map_update_elem(struct bpf_map *map, void *key, void *value,
 		return -EOPNOTSUPP;
 	}
 
-	sock_hold(sock->sk);
+	map_entry = &m->xsk_map[i];
+	node = xsk_map_node_alloc(m, map_entry);
+	if (IS_ERR(node)) {
+		sockfd_put(sock);
+		return PTR_ERR(node);
+	}
 
-	old_xs = xchg(&m->xsk_map[i], xs);
+	spin_lock_bh(&m->lock);
+	old_xs = READ_ONCE(*map_entry);
+	if (old_xs == xs) {
+		err = 0;
+		goto out;
+	}
+	xsk_map_sock_add(xs, node);
+	WRITE_ONCE(*map_entry, xs);
 	if (old_xs)
-		sock_put((struct sock *)old_xs);
-
+		xsk_map_sock_delete(old_xs, map_entry);
+	spin_unlock_bh(&m->lock);
 	sockfd_put(sock);
 	return 0;
+
+out:
+	spin_unlock_bh(&m->lock);
+	sockfd_put(sock);
+	xsk_map_node_free(node);
+	return err;
 }
 
 static int xsk_map_delete_elem(struct bpf_map *map, void *key)
 {
 	struct xsk_map *m = container_of(map, struct xsk_map, map);
-	struct xdp_sock *old_xs;
+	struct xdp_sock *old_xs, **map_entry;
 	int k = *(u32 *)key;
 
 	if (k >= map->max_entries)
 		return -EINVAL;
 
-	old_xs = xchg(&m->xsk_map[k], NULL);
+	spin_lock_bh(&m->lock);
+	map_entry = &m->xsk_map[k];
+	old_xs = xchg(map_entry, NULL);
 	if (old_xs)
-		sock_put((struct sock *)old_xs);
+		xsk_map_sock_delete(old_xs, map_entry);
+	spin_unlock_bh(&m->lock);
 
 	return 0;
 }
 
+void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,
+			     struct xdp_sock **map_entry)
+{
+	spin_lock_bh(&map->lock);
+	if (READ_ONCE(*map_entry) == xs) {
+		WRITE_ONCE(*map_entry, NULL);
+		xsk_map_sock_delete(xs, map_entry);
+	}
+	spin_unlock_bh(&map->lock);
+}
+
 const struct bpf_map_ops xsk_map_ops = {
 	.map_alloc = xsk_map_alloc,
 	.map_free = xsk_map_free,
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 59b57d708697..c3d027aa693d 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -362,6 +362,52 @@ static void xsk_unbind_dev(struct xdp_sock *xs)
 	dev_put(dev);
 }
 
+static struct xsk_map *xsk_get_map_list_entry(struct xdp_sock *xs,
+					      struct xdp_sock ***map_entry)
+{
+	struct xsk_map *map = NULL;
+	struct xsk_map_node *node;
+
+	*map_entry = NULL;
+
+	spin_lock_bh(&xs->map_list_lock);
+	node = list_first_entry_or_null(&xs->map_list, struct xsk_map_node,
+					node);
+	if (node) {
+		WARN_ON(xsk_map_inc(node->map));
+		map = node->map;
+		*map_entry = node->map_entry;
+	}
+	spin_unlock_bh(&xs->map_list_lock);
+	return map;
+}
+
+static void xsk_delete_from_maps(struct xdp_sock *xs)
+{
+	/* This function removes the current XDP socket from all the
+	 * maps it resides in. We need to take extra care here, due to
+	 * the two locks involved. Each map has a lock synchronizing
+	 * updates to the entries, and each socket has a lock that
+	 * synchronizes access to the list of maps (map_list). For
+	 * deadlock avoidance the locks need to be taken in the order
+	 * "map lock"->"socket map list lock". We start off by
+	 * accessing the socket map list, and take a reference to the
+	 * map to guarantee existence between the
+	 * xsk_get_map_list_entry() and xsk_map_try_sock_delete()
+	 * calls. Then we ask the map to remove the socket, which
+	 * tries to remove the socket from the map. Note that there
+	 * might be updates to the map between
+	 * xsk_get_map_list_entry() and xsk_map_try_sock_delete().
+	 */
+	struct xdp_sock **map_entry = NULL;
+	struct xsk_map *map;
+
+	while ((map = xsk_get_map_list_entry(xs, &map_entry))) {
+		xsk_map_try_sock_delete(map, xs, map_entry);
+		xsk_map_put(map);
+	}
+}
+
 static int xsk_release(struct socket *sock)
 {
 	struct sock *sk = sock->sk;
@@ -381,6 +427,7 @@ static int xsk_release(struct socket *sock)
 	sock_prot_inuse_add(net, sk->sk_prot, -1);
 	local_bh_enable();
 
+	xsk_delete_from_maps(xs);
 	xsk_unbind_dev(xs);
 
 	xskq_destroy(xs->rx);
@@ -855,6 +902,9 @@ static int xsk_create(struct net *net, struct socket *sock, int protocol,
 	spin_lock_init(&xs->rx_lock);
 	spin_lock_init(&xs->tx_completion_lock);
 
+	INIT_LIST_HEAD(&xs->map_list);
+	spin_lock_init(&xs->map_list_lock);
+
 	mutex_lock(&net->xdp.lock);
 	sk_add_node_rcu(sk, &net->xdp.list);
 	mutex_unlock(&net->xdp.lock);
-- 
2.20.1


^ permalink raw reply	[flat|nested] 4+ messages in thread

* [PATCH bpf-next v5 2/2] xsk: support BPF_EXIST and BPF_NOEXIST flags in XSKMAP
  2019-08-15  9:30 [PATCH bpf-next v5 0/2] net: xdp: XSKMAP improvements Björn Töpel
  2019-08-15  9:30 ` [PATCH bpf-next v5 1/2] xsk: remove AF_XDP socket from map when the socket is released Björn Töpel
@ 2019-08-15  9:30 ` Björn Töpel
  2019-08-17 21:28 ` [PATCH bpf-next v5 0/2] net: xdp: XSKMAP improvements Daniel Borkmann
  2 siblings, 0 replies; 4+ messages in thread
From: Björn Töpel @ 2019-08-15  9:30 UTC (permalink / raw)
  To: ast, daniel, netdev
  Cc: Björn Töpel, magnus.karlsson, jonathan.lemon,
	bruce.richardson, songliubraving, bpf

From: Björn Töpel <bjorn.topel@intel.com>

The XSKMAP did not honor the BPF_EXIST/BPF_NOEXIST flags when updating
an entry. This patch addresses that.

Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
---
 kernel/bpf/xskmap.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/xskmap.c b/kernel/bpf/xskmap.c
index 16031d489173..4cc28e226398 100644
--- a/kernel/bpf/xskmap.c
+++ b/kernel/bpf/xskmap.c
@@ -226,8 +226,6 @@ static int xsk_map_update_elem(struct bpf_map *map, void *key, void *value,
 		return -EINVAL;
 	if (unlikely(i >= m->map.max_entries))
 		return -E2BIG;
-	if (unlikely(map_flags == BPF_NOEXIST))
-		return -EEXIST;
 
 	sock = sockfd_lookup(fd, &err);
 	if (!sock)
@@ -257,6 +255,12 @@ static int xsk_map_update_elem(struct bpf_map *map, void *key, void *value,
 	if (old_xs == xs) {
 		err = 0;
 		goto out;
+	} else if (old_xs && map_flags == BPF_NOEXIST) {
+		err = -EEXIST;
+		goto out;
+	} else if (!old_xs && map_flags == BPF_EXIST) {
+		err = -ENOENT;
+		goto out;
 	}
 	xsk_map_sock_add(xs, node);
 	WRITE_ONCE(*map_entry, xs);
-- 
2.20.1


^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH bpf-next v5 0/2] net: xdp: XSKMAP improvements
  2019-08-15  9:30 [PATCH bpf-next v5 0/2] net: xdp: XSKMAP improvements Björn Töpel
  2019-08-15  9:30 ` [PATCH bpf-next v5 1/2] xsk: remove AF_XDP socket from map when the socket is released Björn Töpel
  2019-08-15  9:30 ` [PATCH bpf-next v5 2/2] xsk: support BPF_EXIST and BPF_NOEXIST flags in XSKMAP Björn Töpel
@ 2019-08-17 21:28 ` Daniel Borkmann
  2 siblings, 0 replies; 4+ messages in thread
From: Daniel Borkmann @ 2019-08-17 21:28 UTC (permalink / raw)
  To: Björn Töpel, ast, netdev
  Cc: magnus.karlsson, jonathan.lemon, bjorn.topel, bruce.richardson,
	songliubraving, bpf

On 8/15/19 11:30 AM, Björn Töpel wrote:
> This series (v5 and counting) add two improvements for the XSKMAP,
> used by AF_XDP sockets.
> 
> 1. Automatic cleanup when an AF_XDP socket goes out of scope/is
>     released. Instead of require that the user manually clears the
>     "released" state socket from the map, this is done
>     automatically. Each socket tracks which maps it resides in, and
>     remove itself from those maps at relase. A notable implementation
>     change, is that the sockets references the map, instead of the map
>     referencing the sockets. Which implies that when the XSKMAP is
>     freed, it is by definition cleared of sockets.
> 
> 2. The XSKMAP did not honor the BPF_EXIST/BPF_NOEXIST flag on insert,
>     which this patch addresses.
> 
> 
> Thanks,
> Björn
> 
> v1->v2: Fixed deadlock and broken cleanup. (Daniel)
> v2->v3: Rebased onto bpf-next
> v3->v4: {READ, WRITE}_ONCE consistency. (Daniel)
>          Socket release/map update race. (Daniel)
> v4->v5: Avoid use-after-free on XSKMAP self-assignment [1]. (Daniel)
>          Removed redundant assignment in xsk_map_update_elem().
>          Variable name consistency; Use map_entry everywhere.
> 
> [1] https://lore.kernel.org/bpf/20190802081154.30962-1-bjorn.topel@gmail.com/T/#mc68439e97bc07fa301dad9fc4850ed5aa392f385
> 
> Björn Töpel (2):
>    xsk: remove AF_XDP socket from map when the socket is released
>    xsk: support BPF_EXIST and BPF_NOEXIST flags in XSKMAP
> 
>   include/net/xdp_sock.h |  18 ++++++
>   kernel/bpf/xskmap.c    | 133 ++++++++++++++++++++++++++++++++++-------
>   net/xdp/xsk.c          |  50 ++++++++++++++++
>   3 files changed, 179 insertions(+), 22 deletions(-)
> 

Looks better, applied thanks!

^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, back to index

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-15  9:30 [PATCH bpf-next v5 0/2] net: xdp: XSKMAP improvements Björn Töpel
2019-08-15  9:30 ` [PATCH bpf-next v5 1/2] xsk: remove AF_XDP socket from map when the socket is released Björn Töpel
2019-08-15  9:30 ` [PATCH bpf-next v5 2/2] xsk: support BPF_EXIST and BPF_NOEXIST flags in XSKMAP Björn Töpel
2019-08-17 21:28 ` [PATCH bpf-next v5 0/2] net: xdp: XSKMAP improvements Daniel Borkmann

Netdev Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/netdev/0 netdev/git/0.git
	git clone --mirror https://lore.kernel.org/netdev/1 netdev/git/1.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 netdev netdev/ https://lore.kernel.org/netdev \
		netdev@vger.kernel.org netdev@archiver.kernel.org
	public-inbox-index netdev


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.netdev


AGPL code for this site: git clone https://public-inbox.org/ public-inbox