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
..
af_unix.c	af_unix: ensure POLLOUT on remote close() for connected dgram socket	2018-08-03 16:44:19 -07:00
diag.c	net/unix: don't show information about sockets from other namespaces	2017-10-26 10:05:59 +09:00
garbage.c	net: unix: properly re-increment inflight counter of GC discarded candidates	2017-03-21 15:25:10 -07:00
Kconfig	net: Default UDP and UNIX diag to 'n'.	2012-01-07 12:13:06 -08:00
Makefile	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
sysctl_net_unix.c	net: Convert uses of typedef ctl_table to struct ctl_table	2013-06-13 02:36:09 -07:00