linux/include
Johannes Berg ee1c244219 genetlink: synchronize socket closing and family removal
In addition to the problem Jeff Layton reported, I looked at the code
and reproduced the same warning by subscribing and removing the genl
family with a socket still open. This is a fairly tricky race which
originates in the fact that generic netlink allows the family to go
away while sockets are still open - unlike regular netlink which has
a module refcount for every open socket so in general this cannot be
triggered.

Trying to resolve this issue by the obvious locking isn't possible as
it will result in deadlocks between unregistration and group unbind
notification (which incidentally lockdep doesn't find due to the home
grown locking in the netlink table.)

To really resolve this, introduce a "closing socket" reference counter
(for generic netlink only, as it's the only affected family) in the
core netlink code and use that in generic netlink to wait for all the
sockets that are being closed at the same time as a generic netlink
family is removed.

This fixes the race that when a socket is closed, it will should call
the unbind, but if the family is removed at the same time the unbind
will not find it, leading to the warning. The real problem though is
that in this case the unbind could actually find a new family that is
registered to have a multicast group with the same ID, and call its
mcast_unbind() leading to confusing.

Also remove the warning since it would still trigger, but is now no
longer a problem.

This also moves the code in af_netlink.c to before unreferencing the
module to avoid having the same problem in the normal non-genl case.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-01-16 17:04:25 -05:00
..
acpi ACPI / processor: Convert apic_id to phys_id to make it arch agnostic 2015-01-05 23:32:42 +01:00
asm-generic mm: mmu_gather: use tlb->end != 0 only for TLB invalidation 2015-01-13 15:20:40 +13:00
clocksource
crypto crypto: af_alg - add user space interface for AEAD 2014-12-05 23:56:55 +08:00
drm Revert "drm/gem: Warn on illegal use of the dumb buffer interface v2" 2014-12-24 13:13:22 +10:00
dt-bindings Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/evalenti/linux-soc-thermal into thermal-soc 2014-12-21 22:49:12 +08:00
keys
kvm arm/arm64: KVM: Require in-kernel vgic for the arch timers 2014-12-15 11:50:42 +01:00
linux genetlink: synchronize socket closing and family removal 2015-01-16 17:04:25 -05:00
math-emu
media [media] media: v4l2-image-sizes.h: correct the SVGA height definition 2014-12-04 13:56:56 -02:00
memory
misc
net genetlink: synchronize socket closing and family removal 2015-01-16 17:04:25 -05:00
pcmcia
ras
rdma IB/core: Implement support for MMU notifiers regarding on demand paging regions 2014-12-15 18:13:36 -08:00
rxrpc
scsi SCSI for-linus on 20141220 2014-12-20 13:42:57 -08:00
soc Merge branch 'at91/cleanup5' into next/drivers 2014-12-08 18:29:20 +01:00
sound ALSA: pcm: Fix kerneldoc for params_*() functions 2014-12-30 16:41:11 +01:00
target target: Drop left-over fabric_max_sectors attribute 2015-01-09 15:22:05 -08:00
trace SCSI for-linus on 20141220 2014-12-20 13:42:57 -08:00
uapi can: m_can: tag current CAN FD controllers as non-ISO 2015-01-15 16:57:59 +01:00
video OMAPDSS: Remove all references to obsolete HDMI audio callbacks 2014-12-01 11:09:59 +02:00
xen x86/xen: properly retrieve NMI reason 2015-01-13 09:39:50 +00:00
Kbuild