There is a race condition for an established connection that is being closed
by the guest: the refcnt is 4 at the end of hvs_release() (Note: here the
'remove_sock' is false):

1 for the initial value;
1 for the sk being in the bound list;
1 for the sk being in the connected list;
1 for the delayed close_work.

After hvs_release() finishes, __vsock_release() -> sock_put(sk) *may*
decrease the refcnt to 3.

Concurrently, hvs_close_connection() runs in another thread:
  calls vsock_remove_sock() to decrease the refcnt by 2;
  call sock_put() to decrease the refcnt to 0, and free the sk;
  next, the "release_sock(sk)" may hang due to use-after-free.

In the above, after hvs_release() finishes, if hvs_close_connection() runs
faster than "__vsock_release() -> sock_put(sk)", then there is not any issue,
because at the beginning of hvs_close_connection(), the refcnt is still 4.

The issue can be resolved if an extra reference is taken when the
connection is established.

Fixes: a9eeb998c28d ("hv_sock: Add support for delayed close")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Sunil Muthuswamy <sunilmut@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This patch moves the flush of works after vdev->config->del_vqs(vdev),
because we need to be sure that no workers run before to free the
'vsock' object.

Since we stopped the workers using the [tx|rx|event]_run flags,
we are sure no one is accessing the device while we are calling
vdev->config->reset(vdev), so we can safely move the workers' flush.

Before the vdev->config->del_vqs(vdev), workers can be scheduled
by VQ callbacks, so we must flush them after del_vqs(), to avoid
use-after-free of 'vsock' object.

Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Before to call vdev->config->reset(vdev) we need to be sure that
no one is accessing the device, for this reason, we add new variables
in the struct virtio_vsock to stop the workers during the .remove().

This patch also add few comments before vdev->config->reset(vdev)
and vdev->config->del_vqs(vdev).

Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Some callbacks used by the upper layers can run while we are in the
.remove(). A potential use-after-free can happen, because we free
the_virtio_vsock without knowing if the callbacks are over or not.

To solve this issue we move the assignment of the_virtio_vsock at the
end of .probe(), when we finished all the initialization, and at the
beginning of .remove(), before to release resources.
For the same reason, we do the same also for the vdev->priv.

We use RCU to be sure that all callbacks that use the_virtio_vsock
ended before freeing it. This is not required for callbacks that
use vdev->priv, because after the vdev->config->del_vqs() we are sure
that they are ended and will no longer be invoked.

We also take the mutex during the .remove() to avoid that .probe() can
run while we are resetting the device.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Minor SPDX change conflict.

Signed-off-by: David S. Miller <davem@davemloft.net>

Pull networking fixes from David Miller:

 1) Fix leak of unqueued fragments in ipv6 nf_defrag, from Guillaume
    Nault.

 2) Don't access the DDM interface unless the transceiver implements it
    in bnx2x, from Mauro S. M. Rodrigues.

 3) Don't double fetch 'len' from userspace in sock_getsockopt(), from
    JingYi Hou.

 4) Sign extension overflow in lio_core, from Colin Ian King.

 5) Various netem bug fixes wrt. corrupted packets from Jakub Kicinski.

 6) Fix epollout hang in hvsock, from Sunil Muthuswamy.

 7) Fix regression in default fib6_type, from David Ahern.

 8) Handle memory limits in tcp_fragment more appropriately, from Eric
    Dumazet.

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (24 commits)
  tcp: refine memory limit test in tcp_fragment()
  inet: clear num_timeout reqsk_alloc()
  net: mvpp2: debugfs: Add pmap to fs dump
  ipv6: Default fib6_type to RTN_UNICAST when not set
  net: hns3: Fix inconsistent indenting
  net/af_iucv: always register net_device notifier
  net/af_iucv: build proper skbs for HiperTransport
  net/af_iucv: remove GFP_DMA restriction for HiperTransport
  net: dsa: mv88e6xxx: fix shift of FID bits in mv88e6185_g1_vtu_loadpurge()
  hvsock: fix epollout hang from race condition
  net/udp_gso: Allow TX timestamp with UDP GSO
  net: netem: fix use after free and double free with packet corruption
  net: netem: fix backlog accounting for corrupted GSO frames
  net: lio_core: fix potential sign-extension overflow on large shift
  tipc: pass tunnel dev as NULL to udp_tunnel(6)_xmit_skb
  ip6_tunnel: allow not to count pkts on tstats by passing dev as NULL
  ip_tunnel: allow not to count pkts on tstats by setting skb's dev to NULL
  tun: wake up waitqueues after IFF_UP is set
  net: remove duplicate fetch in sock_getsockopt
  tipc: fix issues with early FAILOVER_MSG from peer
  ...

Pull still more SPDX updates from Greg KH:
 "Another round of SPDX updates for 5.2-rc6

  Here is what I am guessing is going to be the last "big" SPDX update
  for 5.2. It contains all of the remaining GPLv2 and GPLv2+ updates
  that were "easy" to determine by pattern matching. The ones after this
  are going to be a bit more difficult and the people on the spdx list
  will be discussing them on a case-by-case basis now.

  Another 5000+ files are fixed up, so our overall totals are:
	Files checked:            64545
	Files with SPDX:          45529

  Compared to the 5.1 kernel which was:
	Files checked:            63848
	Files with SPDX:          22576

  This is a huge improvement.

  Also, we deleted another 20000 lines of boilerplate license crud,
  always nice to see in a diffstat"

* tag 'spdx-5.2-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/spdx: (65 commits)
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 507
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 506
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 505
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 504
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 503
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 502
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 501
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 499
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 498
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 497
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 496
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 495
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 491
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 490
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 489
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 488
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 487
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 486
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 485
  ...

Based on 1 normalized pattern(s):

  this work is licensed under the terms of the gnu gpl version 2

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 48 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Enrico Weigelt <info@metux.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081204.624030236@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Currently, hvsock can enter into a state where epoll_wait on EPOLLOUT will
not return even when the hvsock socket is writable, under some race
condition. This can happen under the following sequence:
- fd = socket(hvsocket)
- fd_out = dup(fd)
- fd_in = dup(fd)
- start a writer thread that writes data to fd_out with a combination of
  epoll_wait(fd_out, EPOLLOUT) and
- start a reader thread that reads data from fd_in with a combination of
  epoll_wait(fd_in, EPOLLIN)
- On the host, there are two threads that are reading/writing data to the
  hvsocket

stack:
hvs_stream_has_space
hvs_notify_poll_out
vsock_poll
sock_poll
ep_poll

Race condition:
check for epollout from ep_poll():
	assume no writable space in the socket
	hvs_stream_has_space() returns 0
check for epollin from ep_poll():
	assume socket has some free space < HVS_PKT_LEN(HVS_SEND_BUF_SIZE)
	hvs_stream_has_space() will clear the channel pending send size
	host will not notify the guest because the pending send size has
		been cleared and so the hvsocket will never mark the
		socket writable

Now, the EPOLLOUT will never return even if the socket write buffer is
empty.

The fix is to set the pending size to the default size and never change it.
This way the host will always notify the guest whenever the writable space
is bigger than the pending size. The host is already optimized to *only*
notify the guest when the pending size threshold boundary is crossed and
not everytime.

This change also reduces the cpu usage somewhat since hv_stream_has_space()
is in the hotpath of send:
vsock_stream_sendmsg()->hv_stream_has_space()
Earlier hv_stream_has_space was setting/clearing the pending size on every
call.

Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Honestly all the conflicts were simple overlapping changes,
nothing really interesting to report.

Signed-off-by: David S. Miller <davem@davemloft.net>