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Date:   Fri, 28 Apr 2023 12:29:50 +0200
From:   Stefano Garzarella <sgarzare@redhat.com>
To:     Bobby Eshleman <bobbyeshleman@gmail.com>
Cc:     Bobby Eshleman <bobby.eshleman@bytedance.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
        Bryan Tan <bryantan@vmware.com>,
        Vishnu Dasa <vdasa@vmware.com>,
        VMware PV-Drivers Reviewers <pv-drivers@vmware.com>,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-hyperv@vger.kernel.org
Subject: Re: [PATCH RFC net-next v2 3/4] vsock: Add lockless sendmsg() support
Message-ID: <se4wymgrmiihkoq4kpnlo2uwklxhfreyzrqjuc7qcqz3c3l7l3@dlxostl5y6q2>
References: <20230413-b4-vsock-dgram-v2-0-079cc7cee62e@bytedance.com>
 <20230413-b4-vsock-dgram-v2-3-079cc7cee62e@bytedance.com>
 <bs3elc4lwvvq22y2vq27ewo23qibei2neys4txszi6wybxpuzu@czyq5hb7iv5t>
 <ZDp837+YDvAfoNLc@bullseye>
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In-Reply-To: <ZDp837+YDvAfoNLc@bullseye>
Precedence: bulk

On Sat, Apr 15, 2023 at 10:30:55AM +0000, Bobby Eshleman wrote:
>On Wed, Apr 19, 2023 at 11:30:53AM +0200, Stefano Garzarella wrote:
>> On Fri, Apr 14, 2023 at 12:25:59AM +0000, Bobby Eshleman wrote:
>> > Because the dgram sendmsg() path for AF_VSOCK acquires the socket lock
>> > it does not scale when many senders share a socket.
>> >
>> > Prior to this patch the socket lock is used to protect the local_addr,
>> > remote_addr, transport, and buffer size variables. What follows are the
>> > new protection schemes for the various protected fields that ensure a
>> > race-free multi-sender sendmsg() path for vsock dgrams.
>> >
>> > - local_addr
>> >    local_addr changes as a result of binding a socket. The write path
>> >    for local_addr is bind() and various vsock_auto_bind() call sites.
>> >    After a socket has been bound via vsock_auto_bind() or bind(), subsequent
>> >    calls to bind()/vsock_auto_bind() do not write to local_addr again. bind()
>> >    rejects the user request and vsock_auto_bind() early exits.
>> >    Therefore, the local addr can not change while a parallel thread is
>> >    in sendmsg() and lock-free reads of local addr in sendmsg() are safe.
>> >    Change: only acquire lock for auto-binding as-needed in sendmsg().
>> >
>> > - vsk->transport
>> >    Updated upon socket creation and it doesn't change again until the
>>
>> This is true only for dgram, right?
>>
>
>Yes.
>
>> How do we decide which transport to assign for dgram?
>>
>
>The transport is assigned in proto->create() [vsock_create()]. It is
>assigned there *only* for dgrams, whereas for streams/seqpackets it is
>assigned in connect(). vsock_create() sets transport to
>'transport_dgram' if sock->type == SOCK_DGRAM.
>
>vsock_sk_destruct() then eventually sets vsk->transport to NULL.
>
>Neither destruct nor create can occur in parallel with sendmsg().
>create() hasn't yet returned the sockfd for the user to call upon it
>sendmsg(), and AFAICT destruct is only called after the final socket
>reference is released, which only happens after the socket no longer
>exists in the fd lookup table and so sendmsg() will fail before it ever
>has the chance to race.

This is okay if a socket can be assigned to a single transport, but with
dgrams I'm not sure we can do that.

Since it is not connected, a socket can send or receive packets from
different transports, so maybe we can't assign it to a specific one,
but do a lookup for every packets to understand which transport to use.

>
>> >    socket is destroyed, which only happens after the socket refcnt reaches
>> >    zero. This prevents any sendmsg() call from being entered because the
>> >    sockfd lookup fails beforehand. That is, sendmsg() and vsk->transport
>> >    writes cannot execute in parallel. Additionally, connect() doesn't
>> >    update vsk->transport for dgrams as it does for streams. Therefore
>> >    vsk->transport is also safe to access lock-free in the sendmsg() path.
>> >    No change.
>> >
>> > - buffer size variables
>> >    Not used by dgram, so they do not need protection. No change.
>>
>> Is this true because for dgram we use the socket buffer?
>> Is it the same for VMCI?
>
>Yes. The buf_alloc derived from buffer_size is also always ignored after
>being initialized once since credits aren't used.
>
>My reading of the VMCI code is that the buffer_size and
>buffer_{min,max}_size variables are used only in connectible calls (like
>connect and recv_listen), but not for datagrams.

Okay, thanks for checking!

>
>>
>> >
>> > - remote_addr
>> >    Needs additional protection because before this patch the
>> >    remote_addr (consisting of several fields such as cid, port, and flags)
>> >    only changed atomically under socket lock context. By acquiring the
>> >    socket lock to read the structure, the changes made by connect() were
>> >    always made visible to sendmsg() atomically. Consequently, to retain
>> >    atomicity of updates but offer lock-free access, this patch
>> >    redesigns this field as an RCU-protected pointer.
>> >
>> >    Writers are still synchronized using the socket lock, but readers
>> >    only read inside RCU read-side critical sections.
>> >
>> > Helpers are introduced for accessing and updating the new pointer.
>> >
>> > The remote_addr structure is wrapped together with an rcu_head into a
>> > sockaddr_vm_rcu structure so that kfree_rcu() can be used. This removes
>> > the need of writers to use synchronize_rcu() after freeing old structures
>> > which is simply more efficient and reduces code churn where remote_addr
>> > is already being updated inside read-side sections.
>> >
>> > Only virtio has been tested, but updates were necessary to the VMCI and
>> > hyperv code. Unfortunately the author does not have access to
>> > VMCI/hyperv systems so those changes are untested.
>> >
>> > Perf Tests
>> > vCPUS: 16
>> > Threads: 16
>> > Payload: 4KB
>> > Test Runs: 5
>> > Type: SOCK_DGRAM
>> >
>> > Before: 245.2 MB/s
>> > After: 509.2 MB/s (+107%)
>> >
>> > Notably, on the same test system, vsock dgram even outperforms
>> > multi-threaded UDP over virtio-net with vhost and MQ support enabled.
>>
>> Cool!
>>
>> This patch is quite large, so I need to review it carefully in future
>> versions, but in general it makes sense to me.
>>
>> Thanks,
>> Stefano
>>
>
>Thanks for the initial comments!
>
>Best,
>Bobby
>
>> >
>> > Throughput metrics for single-threaded SOCK_DGRAM and
>> > single/multi-threaded SOCK_STREAM showed no statistically signficant
>> > throughput changes (lowest p-value reaching 0.27), with the range of the
>> > mean difference ranging between -5% to +1%.
>> >
>> > Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
>> > ---
>> > drivers/vhost/vsock.c                   |  12 +-
>> > include/net/af_vsock.h                  |  19 ++-
>> > net/vmw_vsock/af_vsock.c                | 261 ++++++++++++++++++++++++++++----
>> > net/vmw_vsock/diag.c                    |  10 +-
>> > net/vmw_vsock/hyperv_transport.c        |  15 +-
>> > net/vmw_vsock/virtio_transport_common.c |  22 ++-
>> > net/vmw_vsock/vmci_transport.c          |  70 ++++++---
>> > 7 files changed, 344 insertions(+), 65 deletions(-)
>> >
>> > diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>> > index 028cf079225e..da105cb856ac 100644
>> > --- a/drivers/vhost/vsock.c
>> > +++ b/drivers/vhost/vsock.c
>> > @@ -296,13 +296,17 @@ static int
>> > vhost_transport_cancel_pkt(struct vsock_sock *vsk)
>> > {
>> > 	struct vhost_vsock *vsock;
>> > +	unsigned int cid;
>> > 	int cnt = 0;
>> > 	int ret = -ENODEV;
>> >
>> > 	rcu_read_lock();
>> > +	ret = vsock_remote_addr_cid(vsk, &cid);
>> > +	if (ret < 0)
>> > +		goto out;
>> >
>> > 	/* Find the vhost_vsock according to guest context id  */
>> > -	vsock = vhost_vsock_get(vsk->remote_addr.svm_cid);
>> > +	vsock = vhost_vsock_get(cid);
>> > 	if (!vsock)
>> > 		goto out;
>> >
>> > @@ -686,6 +690,10 @@ static void vhost_vsock_flush(struct vhost_vsock *vsock)
>> > static void vhost_vsock_reset_orphans(struct sock *sk)
>> > {
>> > 	struct vsock_sock *vsk = vsock_sk(sk);
>> > +	unsigned int cid;
>> > +
>> > +	if (vsock_remote_addr_cid(vsk, &cid) < 0)
>> > +		return;
>> >
>> > 	/* vmci_transport.c doesn't take sk_lock here either.  At least we're
>> > 	 * under vsock_table_lock so the sock cannot disappear while we're
>> > @@ -693,7 +701,7 @@ static void vhost_vsock_reset_orphans(struct sock *sk)
>> > 	 */
>> >
>> > 	/* If the peer is still valid, no need to reset connection */
>> > -	if (vhost_vsock_get(vsk->remote_addr.svm_cid))
>> > +	if (vhost_vsock_get(cid))
>> > 		return;
>> >
>> > 	/* If the close timeout is pending, let it expire.  This avoids races
>> > diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
>> > index 57af28fede19..c02fd6ad0047 100644
>> > --- a/include/net/af_vsock.h
>> > +++ b/include/net/af_vsock.h
>> > @@ -25,12 +25,17 @@ extern spinlock_t vsock_table_lock;
>> > #define vsock_sk(__sk)    ((struct vsock_sock *)__sk)
>> > #define sk_vsock(__vsk)   (&(__vsk)->sk)
>> >
>> > +struct sockaddr_vm_rcu {
>> > +	struct sockaddr_vm addr;
>> > +	struct rcu_head rcu;
>> > +};
>> > +
>> > struct vsock_sock {
>> > 	/* sk must be the first member. */
>> > 	struct sock sk;
>> > 	const struct vsock_transport *transport;
>> > 	struct sockaddr_vm local_addr;
>> > -	struct sockaddr_vm remote_addr;
>> > +	struct sockaddr_vm_rcu * __rcu remote_addr;
>> > 	/* Links for the global tables of bound and connected sockets. */
>> > 	struct list_head bound_table;
>> > 	struct list_head connected_table;
>> > @@ -206,7 +211,7 @@ void vsock_release_pending(struct sock *pending);
>> > void vsock_add_pending(struct sock *listener, struct sock *pending);
>> > void vsock_remove_pending(struct sock *listener, struct sock *pending);
>> > void vsock_enqueue_accept(struct sock *listener, struct sock *connected);
>> > -void vsock_insert_connected(struct vsock_sock *vsk);
>> > +int vsock_insert_connected(struct vsock_sock *vsk);
>> > void vsock_remove_bound(struct vsock_sock *vsk);
>> > void vsock_remove_connected(struct vsock_sock *vsk);
>> > struct sock *vsock_find_bound_socket(struct sockaddr_vm *addr);
>> > @@ -244,4 +249,14 @@ static inline void __init vsock_bpf_build_proto(void)
>> > {}
>> > #endif
>> >
>> > +/* RCU-protected remote addr helpers */
>> > +int vsock_remote_addr_cid(struct vsock_sock *vsk, unsigned int *cid);
>> > +int vsock_remote_addr_port(struct vsock_sock *vsk, unsigned int *port);
>> > +int vsock_remote_addr_cid_port(struct vsock_sock *vsk, unsigned int *cid,
>> > +			       unsigned int *port);
>> > +int vsock_remote_addr_copy(struct vsock_sock *vsk, struct sockaddr_vm *dest);
>> > +bool vsock_remote_addr_bound(struct vsock_sock *vsk);
>> > +bool vsock_remote_addr_equals(struct vsock_sock *vsk, struct sockaddr_vm *other);
>> > +int vsock_remote_addr_update_cid_port(struct vsock_sock *vsk, u32 cid, u32 port);
>> > +
>> > #endif /* __AF_VSOCK_H__ */
>> > diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>> > index 46b3f35e3adc..93b4abbf20b4 100644
>> > --- a/net/vmw_vsock/af_vsock.c
>> > +++ b/net/vmw_vsock/af_vsock.c
>> > @@ -145,6 +145,139 @@ static const struct vsock_transport *transport_local;
>> > static DEFINE_MUTEX(vsock_register_mutex);
>> >
>> > /**** UTILS ****/
>> > +bool vsock_remote_addr_bound(struct vsock_sock *vsk)
>> > +{
>> > +	struct sockaddr_vm_rcu *remote_addr;
>> > +	bool ret;
>> > +
>> > +	rcu_read_lock();
>> > +	remote_addr = rcu_dereference(vsk->remote_addr);
>> > +	if (!remote_addr) {
>> > +		rcu_read_unlock();
>> > +		return false;
>> > +	}
>> > +
>> > +	ret = vsock_addr_bound(&remote_addr->addr);
>> > +	rcu_read_unlock();
>> > +
>> > +	return ret;
>> > +}
>> > +EXPORT_SYMBOL_GPL(vsock_remote_addr_bound);
>> > +
>> > +int vsock_remote_addr_copy(struct vsock_sock *vsk, struct sockaddr_vm *dest)
>> > +{
>> > +	struct sockaddr_vm_rcu *remote_addr;
>> > +
>> > +	rcu_read_lock();
>> > +	remote_addr = rcu_dereference(vsk->remote_addr);
>> > +	if (!remote_addr) {
>> > +		rcu_read_unlock();
>> > +		return -EINVAL;
>> > +	}
>> > +	memcpy(dest, &remote_addr->addr, sizeof(*dest));
>> > +	rcu_read_unlock();
>> > +
>> > +	return 0;
>> > +}
>> > +EXPORT_SYMBOL_GPL(vsock_remote_addr_copy);
>> > +
>> > +int vsock_remote_addr_cid(struct vsock_sock *vsk, unsigned int *cid)
>> > +{
>> > +	return vsock_remote_addr_cid_port(vsk, cid, NULL);
>> > +}
>> > +EXPORT_SYMBOL_GPL(vsock_remote_addr_cid);
>> > +
>> > +int vsock_remote_addr_port(struct vsock_sock *vsk, unsigned int *port)
>> > +{
>> > +	return vsock_remote_addr_cid_port(vsk, NULL, port);
>> > +}
>> > +EXPORT_SYMBOL_GPL(vsock_remote_addr_port);
>> > +
>> > +int vsock_remote_addr_cid_port(struct vsock_sock *vsk, unsigned int *cid,
>> > +			       unsigned int *port)
>> > +{
>> > +	struct sockaddr_vm_rcu *remote_addr;
>> > +
>> > +	rcu_read_lock();
>> > +	remote_addr = rcu_dereference(vsk->remote_addr);
>> > +	if (!remote_addr) {
>> > +		rcu_read_unlock();
>> > +		return -EINVAL;
>> > +	}
>> > +
>> > +	if (cid)
>> > +		*cid = remote_addr->addr.svm_cid;
>> > +	if (port)
>> > +		*port = remote_addr->addr.svm_port;
>> > +
>> > +	rcu_read_unlock();
>> > +	return 0;
>> > +}
>> > +EXPORT_SYMBOL_GPL(vsock_remote_addr_cid_port);
>> > +
>> > +/* The socket lock must be held by the caller */
>> > +int vsock_remote_addr_update_cid_port(struct vsock_sock *vsk, u32 cid, u32 port)
>> > +{
>> > +	struct sockaddr_vm_rcu *old, *new;
>> > +
>> > +	new = kmalloc(sizeof(*new), GFP_KERNEL);
>> > +	if (!new)
>> > +		return -ENOMEM;
>> > +
>> > +	rcu_read_lock();
>> > +	old = rcu_dereference(vsk->remote_addr);
>> > +	if (!old) {
>> > +		kfree(new);
>> > +		return -EINVAL;
>> > +	}
>> > +	memcpy(&new->addr, &old->addr, sizeof(new->addr));
>> > +	rcu_read_unlock();
>> > +
>> > +	new->addr.svm_cid = cid;
>> > +	new->addr.svm_port = port;
>> > +
>> > +	old = rcu_replace_pointer(vsk->remote_addr, new, lockdep_sock_is_held(sk_vsock(vsk)));
>> > +	kfree_rcu(old, rcu);
>> > +
>> > +	return 0;
>> > +}
>> > +EXPORT_SYMBOL_GPL(vsock_remote_addr_update_cid_port);
>> > +
>> > +/* The socket lock must be held by the caller */
>> > +int vsock_remote_addr_update(struct vsock_sock *vsk, struct sockaddr_vm *src)
>> > +{
>> > +	struct sockaddr_vm_rcu *old, *new;
>> > +
>> > +	new = kmalloc(sizeof(*new), GFP_KERNEL);
>> > +	if (!new)
>> > +		return -ENOMEM;
>> > +
>> > +	memcpy(&new->addr, src, sizeof(new->addr));
>> > +	old = rcu_replace_pointer(vsk->remote_addr, new, lockdep_sock_is_held(sk_vsock(vsk)));
>> > +	kfree_rcu(old, rcu);
>> > +
>> > +	return 0;
>> > +}
>> > +
>> > +bool vsock_remote_addr_equals(struct vsock_sock *vsk,
>> > +			      struct sockaddr_vm *other)
>> > +{
>> > +	struct sockaddr_vm_rcu *remote_addr;
>> > +	bool equals;
>> > +
>> > +	rcu_read_lock();
>> > +	remote_addr = rcu_dereference(vsk->remote_addr);
>> > +	if (!remote_addr) {
>> > +		rcu_read_unlock();
>> > +		return false;
>> > +	}
>> > +
>> > +	equals = vsock_addr_equals_addr(&remote_addr->addr, other);
>> > +	rcu_read_unlock();
>> > +
>> > +	return equals;
>> > +}
>> > +EXPORT_SYMBOL_GPL(vsock_remote_addr_equals);
>> >
>> > /* Each bound VSocket is stored in the bind hash table and each connected
>> >  * VSocket is stored in the connected hash table.
>> > @@ -254,10 +387,16 @@ static struct sock *__vsock_find_connected_socket(struct sockaddr_vm *src,
>> >
>> > 	list_for_each_entry(vsk, vsock_connected_sockets(src, dst),
>> > 			    connected_table) {
>> > -		if (vsock_addr_equals_addr(src, &vsk->remote_addr) &&
>> > +		struct sockaddr_vm_rcu *remote_addr;
>> > +
>> > +		rcu_read_lock();
>> > +		remote_addr = rcu_dereference(vsk->remote_addr);
>> > +		if (vsock_addr_equals_addr(src, &remote_addr->addr) &&
>> > 		    dst->svm_port == vsk->local_addr.svm_port) {
>> > +			rcu_read_unlock();
>> > 			return sk_vsock(vsk);
>> > 		}
>> > +		rcu_read_unlock();
>> > 	}
>> >
>> > 	return NULL;
>> > @@ -270,14 +409,25 @@ static void vsock_insert_unbound(struct vsock_sock *vsk)
>> > 	spin_unlock_bh(&vsock_table_lock);
>> > }
>> >
>> > -void vsock_insert_connected(struct vsock_sock *vsk)
>> > +int vsock_insert_connected(struct vsock_sock *vsk)
>> > {
>> > -	struct list_head *list = vsock_connected_sockets(
>> > -		&vsk->remote_addr, &vsk->local_addr);
>> > +	struct list_head *list;
>> > +	struct sockaddr_vm_rcu *remote_addr;
>> > +
>> > +	rcu_read_lock();
>> > +	remote_addr = rcu_dereference(vsk->remote_addr);
>> > +	if (!remote_addr) {
>> > +		rcu_read_unlock();
>> > +		return -EINVAL;
>> > +	}
>> > +	list = vsock_connected_sockets(&remote_addr->addr, &vsk->local_addr);
>> > +	rcu_read_unlock();
>> >
>> > 	spin_lock_bh(&vsock_table_lock);
>> > 	__vsock_insert_connected(list, vsk);
>> > 	spin_unlock_bh(&vsock_table_lock);
>> > +
>> > +	return 0;
>> > }
>> > EXPORT_SYMBOL_GPL(vsock_insert_connected);
>> >
>> > @@ -438,10 +588,17 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
>> > {
>> > 	const struct vsock_transport *new_transport;
>> > 	struct sock *sk = sk_vsock(vsk);
>> > -	unsigned int remote_cid = vsk->remote_addr.svm_cid;
>> > +	struct sockaddr_vm remote_addr;
>> > +	unsigned int remote_cid;
>> > 	__u8 remote_flags;
>> > 	int ret;
>> >
>> > +	ret = vsock_remote_addr_copy(vsk, &remote_addr);
>> > +	if (ret < 0)
>> > +		return ret;
>> > +
>> > +	remote_cid = remote_addr.svm_cid;
>> > +
>> > 	/* If the packet is coming with the source and destination CIDs higher
>> > 	 * than VMADDR_CID_HOST, then a vsock channel where all the packets are
>> > 	 * forwarded to the host should be established. Then the host will
>> > @@ -451,10 +608,15 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
>> > 	 * the connect path the flag can be set by the user space application.
>> > 	 */
>> > 	if (psk && vsk->local_addr.svm_cid > VMADDR_CID_HOST &&
>> > -	    vsk->remote_addr.svm_cid > VMADDR_CID_HOST)
>> > -		vsk->remote_addr.svm_flags |= VMADDR_FLAG_TO_HOST;
>> > +	    remote_addr.svm_cid > VMADDR_CID_HOST) {
>> > +		remote_addr.svm_flags |= VMADDR_CID_HOST;
>> > +
>> > +		ret = vsock_remote_addr_update(vsk, &remote_addr);
>> > +		if (ret < 0)
>> > +			return ret;
>> > +	}
>> >
>> > -	remote_flags = vsk->remote_addr.svm_flags;
>> > +	remote_flags = remote_addr.svm_flags;
>> >
>> > 	switch (sk->sk_type) {
>> > 	case SOCK_DGRAM:
>> > @@ -742,6 +904,7 @@ static struct sock *__vsock_create(struct net *net,
>> > 				   unsigned short type,
>> > 				   int kern)
>> > {
>> > +	struct sockaddr_vm *remote_addr;
>> > 	struct sock *sk;
>> > 	struct vsock_sock *psk;
>> > 	struct vsock_sock *vsk;
>> > @@ -761,7 +924,14 @@ static struct sock *__vsock_create(struct net *net,
>> >
>> > 	vsk = vsock_sk(sk);
>> > 	vsock_addr_init(&vsk->local_addr, VMADDR_CID_ANY, VMADDR_PORT_ANY);
>> > -	vsock_addr_init(&vsk->remote_addr, VMADDR_CID_ANY, VMADDR_PORT_ANY);
>> > +
>> > +	remote_addr = kmalloc(sizeof(*remote_addr), GFP_KERNEL);
>> > +	if (!remote_addr) {
>> > +		sk_free(sk);
>> > +		return NULL;
>> > +	}
>> > +	vsock_addr_init(remote_addr, VMADDR_CID_ANY, VMADDR_PORT_ANY);
>> > +	rcu_assign_pointer(vsk->remote_addr, remote_addr);
>> >
>> > 	sk->sk_destruct = vsock_sk_destruct;
>> > 	sk->sk_backlog_rcv = vsock_queue_rcv_skb;
>> > @@ -845,6 +1015,7 @@ static void __vsock_release(struct sock *sk, int level)
>> > static void vsock_sk_destruct(struct sock *sk)
>> > {
>> > 	struct vsock_sock *vsk = vsock_sk(sk);
>> > +	struct sockaddr_vm_rcu *remote_addr;
>> >
>> > 	vsock_deassign_transport(vsk);
>> >
>> > @@ -852,8 +1023,8 @@ static void vsock_sk_destruct(struct sock *sk)
>> > 	 * possibly register the address family with the kernel.
>> > 	 */
>> > 	vsock_addr_init(&vsk->local_addr, VMADDR_CID_ANY, VMADDR_PORT_ANY);
>> > -	vsock_addr_init(&vsk->remote_addr, VMADDR_CID_ANY, VMADDR_PORT_ANY);
>> > -
>> > +	remote_addr = rcu_replace_pointer(vsk->remote_addr, NULL, 1);
>> > +	kfree_rcu(remote_addr);
>> > 	put_cred(vsk->owner);
>> > }
>> >
>> > @@ -943,6 +1114,7 @@ static int vsock_getname(struct socket *sock,
>> > 	struct sock *sk;
>> > 	struct vsock_sock *vsk;
>> > 	struct sockaddr_vm *vm_addr;
>> > +	struct sockaddr_vm_rcu *rcu_ptr;
>> >
>> > 	sk = sock->sk;
>> > 	vsk = vsock_sk(sk);
>> > @@ -951,11 +1123,17 @@ static int vsock_getname(struct socket *sock,
>> > 	lock_sock(sk);
>> >
>> > 	if (peer) {
>> > +		rcu_read_lock();
>> > 		if (sock->state != SS_CONNECTED) {
>> > 			err = -ENOTCONN;
>> > 			goto out;
>> > 		}
>> > -		vm_addr = &vsk->remote_addr;
>> > +		rcu_ptr = rcu_dereference(vsk->remote_addr);
>> > +		if (!rcu_ptr) {
>> > +			err = -EINVAL;
>> > +			goto out;
>> > +		}
>> > +		vm_addr = &rcu_ptr->addr;
>> > 	} else {
>> > 		vm_addr = &vsk->local_addr;
>> > 	}
>> > @@ -975,6 +1153,8 @@ static int vsock_getname(struct socket *sock,
>> > 	err = sizeof(*vm_addr);
>> >
>> > out:
>> > +	if (peer)
>> > +		rcu_read_unlock();
>> > 	release_sock(sk);
>> > 	return err;
>> > }
>> > @@ -1161,7 +1341,7 @@ static int vsock_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
>> > 	int err;
>> > 	struct sock *sk;
>> > 	struct vsock_sock *vsk;
>> > -	struct sockaddr_vm *remote_addr;
>> > +	struct sockaddr_vm stack_addr, *remote_addr;
>> > 	const struct vsock_transport *transport;
>> >
>> > 	if (msg->msg_flags & MSG_OOB)
>> > @@ -1172,15 +1352,26 @@ static int vsock_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
>> > 	sk = sock->sk;
>> > 	vsk = vsock_sk(sk);
>> >
>> > -	lock_sock(sk);
>> > +	/* If auto-binding is required, acquire the slock to avoid potential
>> > +	 * race conditions. Otherwise, do not acquire the lock.
>> > +	 *
>> > +	 * We know that the first check of local_addr is racy (indicated by
>> > +	 * data_race()). By acquiring the lock and then subsequently checking
>> > +	 * again if local_addr is bound (inside vsock_auto_bind()), we can
>> > +	 * ensure there are no real data races.
>> > +	 *
>> > +	 * This technique is borrowed by inet_send_prepare().
>> > +	 */
>> > +	if (data_race(!vsock_addr_bound(&vsk->local_addr))) {
>> > +		lock_sock(sk);
>> > +		err = vsock_auto_bind(vsk);
>> > +		release_sock(sk);
>> > +		if (err)
>> > +			return err;
>> > +	}
>> >
>> > 	transport = vsk->transport;
>> >
>> > -	err = vsock_auto_bind(vsk);
>> > -	if (err)
>> > -		goto out;
>> > -
>> > -
>> > 	/* If the provided message contains an address, use that.  Otherwise
>> > 	 * fall back on the socket's remote handle (if it has been connected).
>> > 	 */
>> > @@ -1199,18 +1390,26 @@ static int vsock_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
>> > 			goto out;
>> > 		}
>> > 	} else if (sock->state == SS_CONNECTED) {
>> > -		remote_addr = &vsk->remote_addr;
>> > +		err = vsock_remote_addr_copy(vsk, &stack_addr);
>> > +		if (err < 0)
>> > +			goto out;
>> >
>> > -		if (remote_addr->svm_cid == VMADDR_CID_ANY)
>> > -			remote_addr->svm_cid = transport->get_local_cid();
>> > +		if (stack_addr.svm_cid == VMADDR_CID_ANY) {
>> > +			stack_addr.svm_cid = transport->get_local_cid();
>> > +			lock_sock(sk_vsock(vsk));
>> > +			vsock_remote_addr_update(vsk, &stack_addr);
>> > +			release_sock(sk_vsock(vsk));
>> > +		}
>> >
>> > 		/* XXX Should connect() or this function ensure remote_addr is
>> > 		 * bound?
>> > 		 */
>> > -		if (!vsock_addr_bound(&vsk->remote_addr)) {
>> > +		if (!vsock_addr_bound(&stack_addr)) {
>> > 			err = -EINVAL;
>> > 			goto out;
>> > 		}
>> > +
>> > +		remote_addr = &stack_addr;
>> > 	} else {
>> > 		err = -EINVAL;
>> > 		goto out;
>> > @@ -1225,7 +1424,6 @@ static int vsock_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
>> > 	err = transport->dgram_enqueue(vsk, remote_addr, msg, len);
>> >
>> > out:
>> > -	release_sock(sk);
>> > 	return err;
>> > }
>> >
>> > @@ -1243,8 +1441,7 @@ static int vsock_dgram_connect(struct socket *sock,
>> > 	err = vsock_addr_cast(addr, addr_len, &remote_addr);
>> > 	if (err == -EAFNOSUPPORT && remote_addr->svm_family == AF_UNSPEC) {
>> > 		lock_sock(sk);
>> > -		vsock_addr_init(&vsk->remote_addr, VMADDR_CID_ANY,
>> > -				VMADDR_PORT_ANY);
>> > +		vsock_remote_addr_update_cid_port(vsk, VMADDR_CID_ANY, VMADDR_PORT_ANY);
>> > 		sock->state = SS_UNCONNECTED;
>> > 		release_sock(sk);
>> > 		return 0;
>> > @@ -1263,7 +1460,10 @@ static int vsock_dgram_connect(struct socket *sock,
>> > 		goto out;
>> > 	}
>> >
>> > -	memcpy(&vsk->remote_addr, remote_addr, sizeof(vsk->remote_addr));
>> > +	err = vsock_remote_addr_update(vsk, remote_addr);
>> > +	if (err < 0)
>> > +		goto out;
>> > +
>> > 	sock->state = SS_CONNECTED;
>> >
>> > 	/* sock map disallows redirection of non-TCP sockets with sk_state !=
>> > @@ -1399,8 +1599,9 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr,
>> > 		}
>> >
>> > 		/* Set the remote address that we are connecting to. */
>> > -		memcpy(&vsk->remote_addr, remote_addr,
>> > -		       sizeof(vsk->remote_addr));
>> > +		err = vsock_remote_addr_update(vsk, remote_addr);
>> > +		if (err)
>> > +			goto out;
>> >
>> > 		err = vsock_assign_transport(vsk, NULL);
>> > 		if (err)
>> > @@ -1831,7 +2032,7 @@ static int vsock_connectible_sendmsg(struct socket *sock, struct msghdr *msg,
>> > 		goto out;
>> > 	}
>> >
>> > -	if (!vsock_addr_bound(&vsk->remote_addr)) {
>> > +	if (!vsock_remote_addr_bound(vsk)) {
>> > 		err = -EDESTADDRREQ;
>> > 		goto out;
>> > 	}
>> > diff --git a/net/vmw_vsock/diag.c b/net/vmw_vsock/diag.c
>> > index a2823b1c5e28..f843bae86b32 100644
>> > --- a/net/vmw_vsock/diag.c
>> > +++ b/net/vmw_vsock/diag.c
>> > @@ -15,8 +15,14 @@ static int sk_diag_fill(struct sock *sk, struct sk_buff *skb,
>> > 			u32 portid, u32 seq, u32 flags)
>> > {
>> > 	struct vsock_sock *vsk = vsock_sk(sk);
>> > +	struct sockaddr_vm remote_addr;
>> > 	struct vsock_diag_msg *rep;
>> > 	struct nlmsghdr *nlh;
>> > +	int err;
>> > +
>> > +	err = vsock_remote_addr_copy(vsk, &remote_addr);
>> > +	if (err < 0)
>> > +		return err;
>> >
>> > 	nlh = nlmsg_put(skb, portid, seq, SOCK_DIAG_BY_FAMILY, sizeof(*rep),
>> > 			flags);
>> > @@ -36,8 +42,8 @@ static int sk_diag_fill(struct sock *sk, struct sk_buff *skb,
>> > 	rep->vdiag_shutdown = sk->sk_shutdown;
>> > 	rep->vdiag_src_cid = vsk->local_addr.svm_cid;
>> > 	rep->vdiag_src_port = vsk->local_addr.svm_port;
>> > -	rep->vdiag_dst_cid = vsk->remote_addr.svm_cid;
>> > -	rep->vdiag_dst_port = vsk->remote_addr.svm_port;
>> > +	rep->vdiag_dst_cid = remote_addr.svm_cid;
>> > +	rep->vdiag_dst_port = remote_addr.svm_port;
>> > 	rep->vdiag_ino = sock_i_ino(sk);
>> >
>> > 	sock_diag_save_cookie(sk, rep->vdiag_cookie);
>> > diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
>> > index 7cb1a9d2cdb4..462b2ec3e6e9 100644
>> > --- a/net/vmw_vsock/hyperv_transport.c
>> > +++ b/net/vmw_vsock/hyperv_transport.c
>> > @@ -336,9 +336,11 @@ static void hvs_open_connection(struct vmbus_channel *chan)
>> > 		hvs_addr_init(&vnew->local_addr, if_type);
>> >
>> > 		/* Remote peer is always the host */
>> > -		vsock_addr_init(&vnew->remote_addr,
>> > -				VMADDR_CID_HOST, VMADDR_PORT_ANY);
>> > -		vnew->remote_addr.svm_port = get_port_by_srv_id(if_instance);
>> > +		ret = vsock_remote_addr_update_cid_port(vnew, VMADDR_CID_HOST,
>> > +							get_port_by_srv_id(if_instance));
>> > +		if (ret < 0)
>> > +			goto out;
>> > +
>> > 		ret = vsock_assign_transport(vnew, vsock_sk(sk));
>> > 		/* Transport assigned (looking at remote_addr) must be the
>> > 		 * same where we received the request.
>> > @@ -459,13 +461,18 @@ static int hvs_connect(struct vsock_sock *vsk)
>> > {
>> > 	union hvs_service_id vm, host;
>> > 	struct hvsock *h = vsk->trans;
>> > +	int err;
>> >
>> > 	vm.srv_id = srv_id_template;
>> > 	vm.svm_port = vsk->local_addr.svm_port;
>> > 	h->vm_srv_id = vm.srv_id;
>> >
>> > 	host.srv_id = srv_id_template;
>> > -	host.svm_port = vsk->remote_addr.svm_port;
>> > +
>> > +	err = vsock_remote_addr_port(vsk, &host.svm_port);
>> > +	if (err < 0)
>> > +		return err;
>> > +
>> > 	h->host_srv_id = host.srv_id;
>> >
>> > 	return vmbus_send_tl_connect_request(&h->vm_srv_id, &h->host_srv_id);
>> > diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>> > index 925acface893..1b87704e516a 100644
>> > --- a/net/vmw_vsock/virtio_transport_common.c
>> > +++ b/net/vmw_vsock/virtio_transport_common.c
>> > @@ -258,8 +258,9 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
>> > 	src_cid = t_ops->transport.get_local_cid();
>> > 	src_port = vsk->local_addr.svm_port;
>> > 	if (!info->remote_cid) {
>> > -		dst_cid	= vsk->remote_addr.svm_cid;
>> > -		dst_port = vsk->remote_addr.svm_port;
>> > +		ret = vsock_remote_addr_cid_port(vsk, &dst_cid, &dst_port);
>> > +		if (ret < 0)
>> > +			return ret;
>> > 	} else {
>> > 		dst_cid = info->remote_cid;
>> > 		dst_port = info->remote_port;
>> > @@ -1169,7 +1170,9 @@ virtio_transport_recv_connecting(struct sock *sk,
>> > 	case VIRTIO_VSOCK_OP_RESPONSE:
>> > 		sk->sk_state = TCP_ESTABLISHED;
>> > 		sk->sk_socket->state = SS_CONNECTED;
>> > -		vsock_insert_connected(vsk);
>> > +		err = vsock_insert_connected(vsk);
>> > +		if (err)
>> > +			goto destroy;
>> > 		sk->sk_state_change(sk);
>> > 		break;
>> > 	case VIRTIO_VSOCK_OP_INVALID:
>> > @@ -1403,9 +1406,8 @@ virtio_transport_recv_listen(struct sock *sk, struct sk_buff *skb,
>> > 	vchild = vsock_sk(child);
>> > 	vsock_addr_init(&vchild->local_addr, le64_to_cpu(hdr->dst_cid),
>> > 			le32_to_cpu(hdr->dst_port));
>> > -	vsock_addr_init(&vchild->remote_addr, le64_to_cpu(hdr->src_cid),
>> > -			le32_to_cpu(hdr->src_port));
>> > -
>> > +	vsock_remote_addr_update_cid_port(vchild, le64_to_cpu(hdr->src_cid),
>> > +					  le32_to_cpu(hdr->src_port));
>> > 	ret = vsock_assign_transport(vchild, vsk);
>> > 	/* Transport assigned (looking at remote_addr) must be the same
>> > 	 * where we received the request.
>> > @@ -1420,7 +1422,13 @@ virtio_transport_recv_listen(struct sock *sk, struct sk_buff *skb,
>> > 	if (virtio_transport_space_update(child, skb))
>> > 		child->sk_write_space(child);
>> >
>> > -	vsock_insert_connected(vchild);
>> > +	ret = vsock_insert_connected(vchild);
>> > +	if (ret) {
>> > +		release_sock(child);
>> > +		virtio_transport_reset_no_sock(t, skb);
>> > +		sock_put(child);
>> > +		return ret;
>> > +	}
>> > 	vsock_enqueue_accept(sk, child);
>> > 	virtio_transport_send_response(vchild, skb);
>> >
>> > diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
>> > index b370070194fa..c0c445e7d925 100644
>> > --- a/net/vmw_vsock/vmci_transport.c
>> > +++ b/net/vmw_vsock/vmci_transport.c
>> > @@ -283,18 +283,25 @@ vmci_transport_send_control_pkt(struct sock *sk,
>> > 				u16 proto,
>> > 				struct vmci_handle handle)
>> > {
>> > +	struct sockaddr_vm addr_stack;
>> > +	struct sockaddr_vm *remote_addr = &addr_stack;
>> > 	struct vsock_sock *vsk;
>> > +	int err;
>> >
>> > 	vsk = vsock_sk(sk);
>> >
>> > 	if (!vsock_addr_bound(&vsk->local_addr))
>> > 		return -EINVAL;
>> >
>> > -	if (!vsock_addr_bound(&vsk->remote_addr))
>> > +	if (!vsock_remote_addr_bound(vsk))
>> > 		return -EINVAL;
>> >
>> > +	err = vsock_remote_addr_copy(vsk, &addr_stack);
>> > +	if (err < 0)
>> > +		return err;
>> > +
>> > 	return vmci_transport_alloc_send_control_pkt(&vsk->local_addr,
>> > -						     &vsk->remote_addr,
>> > +						     remote_addr,
>> > 						     type, size, mode,
>> > 						     wait, proto, handle);
>> > }
>> > @@ -317,6 +324,7 @@ static int vmci_transport_send_reset(struct sock *sk,
>> > 	struct sockaddr_vm *dst_ptr;
>> > 	struct sockaddr_vm dst;
>> > 	struct vsock_sock *vsk;
>> > +	int err;
>> >
>> > 	if (pkt->type == VMCI_TRANSPORT_PACKET_TYPE_RST)
>> > 		return 0;
>> > @@ -326,13 +334,16 @@ static int vmci_transport_send_reset(struct sock *sk,
>> > 	if (!vsock_addr_bound(&vsk->local_addr))
>> > 		return -EINVAL;
>> >
>> > -	if (vsock_addr_bound(&vsk->remote_addr)) {
>> > -		dst_ptr = &vsk->remote_addr;
>> > +	if (vsock_remote_addr_bound(vsk)) {
>> > +		err = vsock_remote_addr_copy(vsk, &dst);
>> > +		if (err < 0)
>> > +			return err;
>> > 	} else {
>> > 		vsock_addr_init(&dst, pkt->dg.src.context,
>> > 				pkt->src_port);
>> > -		dst_ptr = &dst;
>> > 	}
>> > +	dst_ptr = &dst;
>> > +
>> > 	return vmci_transport_alloc_send_control_pkt(&vsk->local_addr, dst_ptr,
>> > 					     VMCI_TRANSPORT_PACKET_TYPE_RST,
>> > 					     0, 0, NULL, VSOCK_PROTO_INVALID,
>> > @@ -490,7 +501,7 @@ static struct sock *vmci_transport_get_pending(
>> >
>> > 	list_for_each_entry(vpending, &vlistener->pending_links,
>> > 			    pending_links) {
>> > -		if (vsock_addr_equals_addr(&src, &vpending->remote_addr) &&
>> > +		if (vsock_remote_addr_equals(vpending, &src) &&
>> > 		    pkt->dst_port == vpending->local_addr.svm_port) {
>> > 			pending = sk_vsock(vpending);
>> > 			sock_hold(pending);
>> > @@ -1015,8 +1026,8 @@ static int vmci_transport_recv_listen(struct sock *sk,
>> >
>> > 	vsock_addr_init(&vpending->local_addr, pkt->dg.dst.context,
>> > 			pkt->dst_port);
>> > -	vsock_addr_init(&vpending->remote_addr, pkt->dg.src.context,
>> > -			pkt->src_port);
>> > +	vsock_remote_addr_update_cid_port(vpending, pkt->dg.src.context,
>> > +					  pkt->src_port);
>> >
>> > 	err = vsock_assign_transport(vpending, vsock_sk(sk));
>> > 	/* Transport assigned (looking at remote_addr) must be the same
>> > @@ -1133,6 +1144,7 @@ vmci_transport_recv_connecting_server(struct sock *listener,
>> > {
>> > 	struct vsock_sock *vpending;
>> > 	struct vmci_handle handle;
>> > +	unsigned int vpending_remote_cid;
>> > 	struct vmci_qp *qpair;
>> > 	bool is_local;
>> > 	u32 flags;
>> > @@ -1189,8 +1201,13 @@ vmci_transport_recv_connecting_server(struct sock *listener,
>> > 	/* vpending->local_addr always has a context id so we do not need to
>> > 	 * worry about VMADDR_CID_ANY in this case.
>> > 	 */
>> > -	is_local =
>> > -	    vpending->remote_addr.svm_cid == vpending->local_addr.svm_cid;
>> > +	err = vsock_remote_addr_cid(vpending, &vpending_remote_cid);
>> > +	if (err < 0) {
>> > +		skerr = EPROTO;
>> > +		goto destroy;
>> > +	}
>> > +
>> > +	is_local = vpending_remote_cid == vpending->local_addr.svm_cid;
>> > 	flags = VMCI_QPFLAG_ATTACH_ONLY;
>> > 	flags |= is_local ? VMCI_QPFLAG_LOCAL : 0;
>> >
>> > @@ -1203,7 +1220,7 @@ vmci_transport_recv_connecting_server(struct sock *listener,
>> > 					flags,
>> > 					vmci_transport_is_trusted(
>> > 						vpending,
>> > -						vpending->remote_addr.svm_cid));
>> > +						vpending_remote_cid));
>> > 	if (err < 0) {
>> > 		vmci_transport_send_reset(pending, pkt);
>> > 		skerr = -err;
>> > @@ -1306,9 +1323,20 @@ vmci_transport_recv_connecting_client(struct sock *sk,
>> > 		break;
>> > 	case VMCI_TRANSPORT_PACKET_TYPE_NEGOTIATE:
>> > 	case VMCI_TRANSPORT_PACKET_TYPE_NEGOTIATE2:
>> > +		struct sockaddr_vm_rcu *remote_addr;
>> > +
>> > +		rcu_read_lock();
>> > +		remote_addr = rcu_dereference(vsk->remote_addr);
>> > +		if (!remote_addr) {
>> > +			skerr = EPROTO;
>> > +			err = -EINVAL;
>> > +			rcu_read_unlock();
>> > +			goto destroy;
>> > +		}
>> > +
>> > 		if (pkt->u.size == 0
>> > -		    || pkt->dg.src.context != vsk->remote_addr.svm_cid
>> > -		    || pkt->src_port != vsk->remote_addr.svm_port
>> > +		    || pkt->dg.src.context != remote_addr->addr.svm_cid
>> > +		    || pkt->src_port != remote_addr->addr.svm_port
>> > 		    || !vmci_handle_is_invalid(vmci_trans(vsk)->qp_handle)
>> > 		    || vmci_trans(vsk)->qpair
>> > 		    || vmci_trans(vsk)->produce_size != 0
>> > @@ -1316,9 +1344,10 @@ vmci_transport_recv_connecting_client(struct sock *sk,
>> > 		    || vmci_trans(vsk)->detach_sub_id != VMCI_INVALID_ID) {
>> > 			skerr = EPROTO;
>> > 			err = -EINVAL;
>> > -
>> > +			rcu_read_unlock();
>> > 			goto destroy;
>> > 		}
>> > +		rcu_read_unlock();
>> >
>> > 		err = vmci_transport_recv_connecting_client_negotiate(sk, pkt);
>> > 		if (err) {
>> > @@ -1379,6 +1408,7 @@ static int vmci_transport_recv_connecting_client_negotiate(
>> > 	int err;
>> > 	struct vsock_sock *vsk;
>> > 	struct vmci_handle handle;
>> > +	unsigned int remote_cid;
>> > 	struct vmci_qp *qpair;
>> > 	u32 detach_sub_id;
>> > 	bool is_local;
>> > @@ -1449,19 +1479,23 @@ static int vmci_transport_recv_connecting_client_negotiate(
>> >
>> > 	/* Make VMCI select the handle for us. */
>> > 	handle = VMCI_INVALID_HANDLE;
>> > -	is_local = vsk->remote_addr.svm_cid == vsk->local_addr.svm_cid;
>> > +
>> > +	err = vsock_remote_addr_cid(vsk, &remote_cid);
>> > +	if (err < 0)
>> > +		goto destroy;
>> > +
>> > +	is_local = remote_cid == vsk->local_addr.svm_cid;
>> > 	flags = is_local ? VMCI_QPFLAG_LOCAL : 0;
>> >
>> > 	err = vmci_transport_queue_pair_alloc(&qpair,
>> > 					      &handle,
>> > 					      pkt->u.size,
>> > 					      pkt->u.size,
>> > -					      vsk->remote_addr.svm_cid,
>> > +					      remote_cid,
>> > 					      flags,
>> > 					      vmci_transport_is_trusted(
>> > 						  vsk,
>> > -						  vsk->
>> > -						  remote_addr.svm_cid));
>> > +						  remote_cid));
>> > 	if (err < 0)
>> > 		goto destroy;
>> >
>> >
>> > --
>> > 2.30.2
>> >
>>
>