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Date: Thu, 26 Nov 2015 14:32:40 +0100
From: Hannes Frederic Sowa <hannes@...essinduktion.org>
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: Rainer Weikusat <rweikusat@...ileactivedefense.com>,
Eric Dumazet <edumazet@...gle.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Benjamin LaHaise <bcrl@...ck.org>,
"David S. Miller" <davem@...emloft.net>,
Al Viro <viro@...iv.linux.org.uk>,
David Howells <dhowells@...hat.com>,
Ying Xue <ying.xue@...driver.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
netdev <netdev@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
syzkaller <syzkaller@...glegroups.com>,
Kostya Serebryany <kcc@...gle.com>,
Alexander Potapenko <glider@...gle.com>,
Sasha Levin <sasha.levin@...cle.com>
Subject: Re: use-after-free in sock_wake_async
Hannes Frederic Sowa <hannes@...essinduktion.org> writes:
> I have seen filesystems already doing so in .destroy_inode, that's why I
> am asking. The allocation happens the same way as we do with sock_alloc,
> e.g. shmem. I actually thought that struct inode already provides an
> rcu_head for exactly that reason.
E.g.:
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 54036ae..e15c49f 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -35,7 +35,6 @@
struct macvtap_queue {
struct sock sk;
struct socket sock;
- struct socket_wq wq;
int vnet_hdr_sz;
struct macvlan_dev __rcu *vlan;
struct file *file;
@@ -529,8 +528,7 @@ static int macvtap_open(struct inode *inode, struct file *file)
if (!q)
goto out;
- RCU_INIT_POINTER(q->sock.wq, &q->wq);
- init_waitqueue_head(&q->wq.wait);
+ init_waitqueue_head(&q->sock.wq.wait);
q->sock.type = SOCK_RAW;
q->sock.state = SS_CONNECTED;
q->sock.file = file;
@@ -579,7 +577,7 @@ static unsigned int macvtap_poll(struct file *file, poll_table * wait)
goto out;
mask = 0;
- poll_wait(file, &q->wq.wait, wait);
+ poll_wait(file, &q->sock.wq.wait, wait);
if (!skb_queue_empty(&q->sk.sk_receive_queue))
mask |= POLLIN | POLLRDNORM;
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index b1878fa..20c5d34 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -145,7 +145,6 @@ struct tap_filter {
struct tun_file {
struct sock sk;
struct socket socket;
- struct socket_wq wq;
struct tun_struct __rcu *tun;
struct fasync_struct *fasync;
/* only used for fasnyc */
@@ -2219,8 +2218,7 @@ static int tun_chr_open(struct inode *inode, struct file * file)
tfile->flags = 0;
tfile->ifindex = 0;
- init_waitqueue_head(&tfile->wq.wait);
- RCU_INIT_POINTER(tfile->socket.wq, &tfile->wq);
+ init_waitqueue_head(&tfile->socket.wq.wait);
tfile->socket.file = file;
tfile->socket.ops = &tun_socket_ops;
diff --git a/include/linux/net.h b/include/linux/net.h
index 70ac5e2..3a7a4d1 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -89,8 +89,7 @@ struct socket_wq {
/* Note: wait MUST be first field of socket_wq */
wait_queue_head_t wait;
struct fasync_struct *fasync_list;
- struct rcu_head rcu;
-} ____cacheline_aligned_in_smp;
+};
/**
* struct socket - general BSD socket
@@ -111,7 +110,7 @@ struct socket {
unsigned long flags;
- struct socket_wq __rcu *wq;
+ struct socket_wq wq;
struct file *file;
struct sock *sk;
diff --git a/include/net/sock.h b/include/net/sock.h
index 7f89e4b..ae34da1 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1674,7 +1674,7 @@ static inline void sock_orphan(struct sock *sk)
static inline void sock_graft(struct sock *sk, struct socket *parent)
{
write_lock_bh(&sk->sk_callback_lock);
- sk->sk_wq = parent->wq;
+ sk->sk_wq = &parent->wq;
parent->sk = sk;
sk_set_socket(sk, parent);
security_sock_graft(sk, parent);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 630c197..c125881 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -657,7 +657,7 @@ static void rcu_preempt_do_callbacks(void)
/*
* Queue a preemptible-RCU callback for invocation after a grace period.
*/
-void call_rcu(struct rcu_head *head, rcu_callback_t func)
+static void call_rcu(struct rcu_head *head, rcu_callback_t func)
{
__call_rcu(head, func, rcu_state_p, -1, 0);
}
diff --git a/net/core/sock.c b/net/core/sock.c
index 1e4dd54..314ab6a 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2383,7 +2383,7 @@ void sock_init_data(struct socket *sock, struct sock *sk)
if (sock) {
sk->sk_type = sock->type;
- sk->sk_wq = sock->wq;
+ sk->sk_wq = &sock->wq;
sock->sk = sk;
} else
sk->sk_wq = NULL;
diff --git a/net/socket.c b/net/socket.c
index dd2c247..495485e 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -245,19 +245,12 @@ static struct kmem_cache *sock_inode_cachep __read_mostly;
static struct inode *sock_alloc_inode(struct super_block *sb)
{
struct socket_alloc *ei;
- struct socket_wq *wq;
ei = kmem_cache_alloc(sock_inode_cachep, GFP_KERNEL);
if (!ei)
return NULL;
- wq = kmalloc(sizeof(*wq), GFP_KERNEL);
- if (!wq) {
- kmem_cache_free(sock_inode_cachep, ei);
- return NULL;
- }
- init_waitqueue_head(&wq->wait);
- wq->fasync_list = NULL;
- RCU_INIT_POINTER(ei->socket.wq, wq);
+ init_waitqueue_head(&ei->socket.wq.wait);
+ ei->socket.wq.fasync_list = NULL;
ei->socket.state = SS_UNCONNECTED;
ei->socket.flags = 0;
@@ -268,17 +261,18 @@ static struct inode *sock_alloc_inode(struct super_block *sb)
return &ei->vfs_inode;
}
-static void sock_destroy_inode(struct inode *inode)
+static void sock_cache_free_rcu(struct rcu_head *rcu)
{
- struct socket_alloc *ei;
- struct socket_wq *wq;
-
- ei = container_of(inode, struct socket_alloc, vfs_inode);
- wq = rcu_dereference_protected(ei->socket.wq, 1);
- kfree_rcu(wq, rcu);
+ struct socket_alloc *ei =
+ container_of(rcu, struct socket_alloc, vfs_inode.i_rcu);
kmem_cache_free(sock_inode_cachep, ei);
}
+static void sock_destroy_inode(struct inode *inode)
+{
+ call_rcu(&inode->i_rcu, sock_cache_free_rcu);
+}
+
static void init_once(void *foo)
{
struct socket_alloc *ei = (struct socket_alloc *)foo;
@@ -573,7 +567,7 @@ void sock_release(struct socket *sock)
module_put(owner);
}
- if (rcu_dereference_protected(sock->wq, 1)->fasync_list)
+ if (sock->wq.fasync_list)
pr_err("%s: fasync list not empty!\n", __func__);
this_cpu_sub(sockets_in_use, 1);
@@ -1044,7 +1038,7 @@ static int sock_fasync(int fd, struct file *filp, int on)
return -EINVAL;
lock_sock(sk);
- wq = rcu_dereference_protected(sock->wq, sock_owned_by_user(sk));
+ wq = &sock->wq;
fasync_helper(fd, filp, on, &wq->fasync_list);
if (!wq->fasync_list)
@@ -1065,7 +1059,7 @@ int sock_wake_async(struct socket *sock, int how, int band)
if (!sock)
return -1;
rcu_read_lock();
- wq = rcu_dereference(sock->wq);
+ wq = &sock->wq;
if (!wq || !wq->fasync_list) {
rcu_read_unlock();
return -1;
--
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