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Dexuan Cui 8aa07625eb hv_netvsc: Fix a deadlock by getting rtnl lock earlier in netvsc_probe() 
[ Upstream commit e04e7a7bbd ]

This patch fixes the race between netvsc_probe() and
rndis_set_subchannel(), which can cause a deadlock.

These are the related 3 paths which show the deadlock:

path #1:
    Workqueue: hv_vmbus_con vmbus_onmessage_work [hv_vmbus]
    Call Trace:
     schedule
     schedule_preempt_disabled
     __mutex_lock
     __device_attach
     bus_probe_device
     device_add
     vmbus_device_register
     vmbus_onoffer
     vmbus_onmessage_work
     process_one_work
     worker_thread
     kthread
     ret_from_fork

path #2:
    schedule
     schedule_preempt_disabled
     __mutex_lock
     netvsc_probe
     vmbus_probe
     really_probe
     __driver_attach
     bus_for_each_dev
     driver_attach_async
     async_run_entry_fn
     process_one_work
     worker_thread
     kthread
     ret_from_fork

path #3:
    Workqueue: events netvsc_subchan_work [hv_netvsc]
    Call Trace:
     schedule
     rndis_set_subchannel
     netvsc_subchan_work
     process_one_work
     worker_thread
     kthread
     ret_from_fork

Before path #1 finishes, path #2 can start to run, because just before
the "bus_probe_device(dev);" in device_add() in path #1, there is a line
"object_uevent(&dev->kobj, KOBJ_ADD);", so systemd-udevd can
immediately try to load hv_netvsc and hence path #2 can start to run.

Next, path #2 offloads the subchannal's initialization to a workqueue,
i.e. path #3, so we can end up in a deadlock situation like this:

Path #2 gets the device lock, and is trying to get the rtnl lock;
Path #3 gets the rtnl lock and is waiting for all the subchannel messages
to be processed;
Path #1 is trying to get the device lock, but since #2 is not releasing
the device lock, path #1 has to sleep; since the VMBus messages are
processed one by one, this means the sub-channel messages can't be
procedded, so #3 has to sleep with the rtnl lock held, and finally #2
has to sleep... Now all the 3 paths are sleeping and we hit the deadlock.

With the patch, we can make sure #2 gets both the device lock and the
rtnl lock together, gets its job done, and releases the locks, so #1
and #3 will not be blocked for ever.

Fixes: 8195b1396e ("hv_netvsc: fix deadlock on hotplug")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-09-15 09:45:26 +02:00
arch arm64: mm: always enable CONFIG_HOLES_IN_ZONE 2018-09-09 19:56:02 +02:00
block block, bfq: return nbytes and not zero from struct cftype .write() method 2018-09-09 19:55:59 +02:00
certs Replace magic for trusting the secondary keyring with #define 2018-09-09 19:55:54 +02:00
crypto Replace magic for trusting the secondary keyring with #define 2018-09-09 19:55:54 +02:00
Documentation kbuild: verify that $DEPMOD is installed 2018-08-17 21:01:10 +02:00
drivers hv_netvsc: Fix a deadlock by getting rtnl lock earlier in netvsc_probe() 2018-09-15 09:45:26 +02:00
firmware License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs fs/quota: Fix spectre gadget in do_quotactl 2018-09-09 19:56:02 +02:00
include r8169: add support for NCube 8168 network card 2018-09-15 09:45:25 +02:00
init init: rename and re-order boot_cpu_state_init() 2018-08-15 18:12:48 +02:00
ipc ipc/sem.c: prevent queue.status tearing in semop 2018-09-05 09:26:30 +02:00
kernel userns: move user access out of the mutex 2018-09-09 19:56:00 +02:00
lib printk/nmi: Prevent deadlock when accessing the main log buffer in NMI 2018-09-05 09:26:35 +02:00
mm mm/tlb: Remove tlb_remove_table() non-concurrent condition 2018-09-09 19:55:59 +02:00
net sctp: hold transport before accessing its asoc in sctp_transport_get_next 2018-09-15 09:45:25 +02:00
samples samples/bpf: Check the error of write() and read() 2018-08-24 13:09:12 +02:00
scripts gcc-plugins: Use dynamic initializers 2018-09-05 09:26:42 +02:00
security cap_inode_getsecurity: use d_find_any_alias() instead of d_find_alias() 2018-09-09 19:56:01 +02:00
sound ASoC: sirf: Fix potential NULL pointer dereference 2018-09-05 09:26:39 +02:00
tools perf auxtrace: Fix queue resize 2018-09-09 19:56:01 +02:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt KVM: arm/arm64: Skip updating PTE entry if no change 2018-09-05 09:26:36 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: rpm-pkg: keep spec file until make mrproper 2018-02-13 10:19:46 +01:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS dt-bindings: Document mti,mips-cpc binding 2018-03-15 10:54:35 +01:00
Makefile Linux 4.14.69 2018-09-09 19:56:02 +02:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

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.