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Filename Latest commit message Latest commit date
Jason Baron 51f7e95187 af_unix: ensure POLLOUT on remote close() for connected dgram socket
Applications use -ECONNREFUSED as returned from write() in order to
determine that a socket should be closed. However, when using connected
dgram unix sockets in a poll/write loop, a final POLLOUT event can be
missed when the remote end closes. Thus, the poll is stuck forever:

          thread 1 (client)                   thread 2 (server)

connect() to server
write() returns -EAGAIN
unix_dgram_poll()
 -> unix_recvq_full() is true
                                       close()
                                        ->unix_release_sock()
                                         ->wake_up_interruptible_all()
unix_dgram_poll() (due to the
     wake_up_interruptible_all)
 -> unix_recvq_full() still is true
                                         ->free all skbs

Now thread 1 is stuck and will not receive anymore wakeups. In this
case, when thread 1 gets the -EAGAIN, it has not queued any skbs
otherwise the 'free all skbs' step would in fact cause a wakeup and
a POLLOUT return. So the race here is probably fairly rare because
it means there are no skbs that thread 1 queued and that thread 1
schedules before the 'free all skbs' step.

This issue was reported as a hang when /dev/log is closed.

The fix is to signal POLLOUT if the socket is marked as SOCK_DEAD, which
means a subsequent write() will get -ECONNREFUSED.

Reported-by: Ian Lance Taylor <iant@golang.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Rainer Weikusat <rweikusat@mobileactivedefense.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jason Baron <jbaron@akamai.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-08-03 16:44:19 -07:00
arch arm64: dts: Fix the base address of the Broadcom iProc mdio mux 2018-08-02 14:36:49 -07:00
block
certs
crypto
Documentation dt-bindings: net: Add clock handle to Broadcom iProc mdio mux 2018-08-02 14:36:49 -07:00
drivers ppp: mppe: Remove VLA usage 2018-08-03 12:54:54 -07:00
firmware
fs rxrpc: Push iov_iter up from rxrpc_kernel_recv_data() to caller 2018-08-03 12:46:20 -07:00
include rxrpc: Push iov_iter up from rxrpc_kernel_recv_data() to caller 2018-08-03 12:46:20 -07:00
init
ipc Merge ra.kernel.org:/pub/scm/linux/kernel/git/davem/net 2018-08-02 10:55:32 -07:00
kernel Merge ra.kernel.org:/pub/scm/linux/kernel/git/davem/net 2018-08-02 10:55:32 -07:00
lib Merge ra.kernel.org:/pub/scm/linux/kernel/git/davem/net 2018-08-02 10:55:32 -07:00
LICENSES
mm
net af_unix: ensure POLLOUT on remote close() for connected dgram socket 2018-08-03 16:44:19 -07:00
samples
scripts
security
sound
tools tools: bpf: fix BTF code added twice to different trees 2018-08-02 19:45:14 -07:00
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Merge ra.kernel.org:/pub/scm/linux/kernel/git/davem/net 2018-08-02 10:55:32 -07:00
Makefile
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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.