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Sebastien Boeuf aed60a1746 net: virtio_vsock: Enhance connection semantics
[ Upstream commit df12eb6d6cd920ab2f0e0a43cd6e1c23a05cea91 ]

Whenever the vsock backend on the host sends a packet through the RX
queue, it expects an answer on the TX queue. Unfortunately, there is one
case where the host side will hang waiting for the answer and might
effectively never recover if no timeout mechanism was implemented.

This issue happens when the guest side starts binding to the socket,
which insert a new bound socket into the list of already bound sockets.
At this time, we expect the guest to also start listening, which will
trigger the sk_state to move from TCP_CLOSE to TCP_LISTEN. The problem
occurs if the host side queued a RX packet and triggered an interrupt
right between the end of the binding process and the beginning of the
listening process. In this specific case, the function processing the
packet virtio_transport_recv_pkt() will find a bound socket, which means
it will hit the switch statement checking for the sk_state, but the
state won't be changed into TCP_LISTEN yet, which leads the code to pick
the default statement. This default statement will only free the buffer,
while it should also respond to the host side, by sending a packet on
its TX queue.

In order to simply fix this unfortunate chain of events, it is important
that in case the default statement is entered, and because at this stage
we know the host side is waiting for an answer, we must send back a
packet containing the operation VIRTIO_VSOCK_OP_RST.

One could say that a proper timeout mechanism on the host side will be
enough to avoid the backend to hang. But the point of this patch is to
ensure the normal use case will be provided with proper responsiveness
when it comes to establishing the connection.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-10-07 08:01:24 +02:00
arch KVM: arm64: Assume write fault on S1PTW permission fault on instruction fetch 2020-10-01 13:18:25 +02:00
block block: only call sched requeue_request() for scheduled requests 2020-09-23 12:40:37 +02:00
certs
crypto crypto: af_alg - Work around empty control messages without MSG_MORE 2020-09-03 11:27:05 +02:00
Documentation ata: make qc_prep return ata_completion_errors 2020-10-01 13:18:26 +02:00
drivers vsock/virtio: add transport parameter to the virtio_transport_reset_no_sock() 2020-10-07 08:01:24 +02:00
fs btrfs: fix filesystem corruption after a device replace 2020-10-07 08:01:23 +02:00
include vsock/virtio: add transport parameter to the virtio_transport_reset_no_sock() 2020-10-07 08:01:24 +02:00
init kprobes: tracing/kprobes: Fix to kill kprobes on initmem after boot 2020-10-01 13:18:23 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel kprobes: Fix compiler warning for !CONFIG_KPROBES_ON_FTRACE 2020-10-01 13:18:25 +02:00
lib lib/string.c: implement stpcpy 2020-10-01 13:18:23 +02:00
LICENSES
mm mm/gup: fix gup_fast with dynamic page table folding 2020-10-01 13:18:24 +02:00
net net: virtio_vsock: Enhance connection semantics 2020-10-07 08:01:24 +02:00
samples bpf: Fix fds_example SIGSEGV error 2020-08-19 08:16:03 +02:00
scripts checkpatch: fix the usage of capture group ( ... ) 2020-09-09 19:12:37 +02:00
security device_cgroup: Fix RCU list debugging warning 2020-10-01 13:18:13 +02:00
sound ALSA: hda/realtek: Enable front panel headset LED on Lenovo ThinkStation P520 2020-10-01 13:18:22 +02:00
tools objtool: Fix noreturn detection for ignored functions 2020-10-01 13:18:15 +02:00
usr
virt KVM: arm64: Assume write fault on S1PTW permission fault on instruction fetch 2020-10-01 13:18:25 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.69 2020-10-01 13:19:27 +02:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.