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Filename Latest commit message Latest commit date
Florian Westphal 1b0890cd60 netfilter: nfnetlink: avoid deadlock due to synchronous request_module
Thomas and Juliana report a deadlock when running:

(rmmod nf_conntrack_netlink/xfrm_user)

  conntrack -e NEW -E &
  modprobe -v xfrm_user

They provided following analysis:

conntrack -e NEW -E
    netlink_bind()
        netlink_lock_table() -> increases "nl_table_users"
            nfnetlink_bind()
            # does not unlock the table as it's locked by netlink_bind()
                __request_module()
                    call_usermodehelper_exec()

This triggers "modprobe nf_conntrack_netlink" from kernel, netlink_bind()
won't return until modprobe process is done.

"modprobe xfrm_user":
    xfrm_user_init()
        register_pernet_subsys()
            -> grab pernet_ops_rwsem
                ..
                netlink_table_grab()
                    calls schedule() as "nl_table_users" is non-zero

so modprobe is blocked because netlink_bind() increased
nl_table_users while also holding pernet_ops_rwsem.

"modprobe nf_conntrack_netlink" runs and inits nf_conntrack_netlink:
    ctnetlink_init()
        register_pernet_subsys()
            -> blocks on "pernet_ops_rwsem" thanks to xfrm_user module

both modprobe processes wait on one another -- neither can make
progress.

Switch netlink_bind() to "nowait" modprobe -- this releases the netlink
table lock, which then allows both modprobe instances to complete.

Reported-by: Thomas Jarosch <thomas.jarosch@intra2net.com>
Reported-by: Juliana Rodrigueiro <juliana.rodrigueiro@intra2net.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2019-07-15 07:56:58 +02:00
arch powerpc updates for 5.3 2019-07-13 16:08:36 -07:00
block for-5.3/block-20190708 2019-07-09 10:45:06 -07:00
certs Revert "Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs" 2019-07-10 18:43:43 -07:00
crypto USB / PHY patches for 5.3-rc1 2019-07-11 15:40:06 -07:00
Documentation bonding: add documentation for peer_notif_delay 2019-07-13 19:29:21 -07:00
drivers sky2: Disable MSI on P5W DH Deluxe 2019-07-14 13:45:54 -07:00
fs for-5.3/io_uring-20190711 2019-07-13 10:36:53 -07:00
include powerpc updates for 5.3 2019-07-13 16:08:36 -07:00
init Kbuild updates for v5.3 2019-07-12 16:03:16 -07:00
ipc
kernel Kbuild updates for v5.3 2019-07-12 16:03:16 -07:00
lib for-5.3/io_uring-20190711 2019-07-13 10:36:53 -07:00
LICENSES
mm Driver Core and debugfs changes for 5.3-rc1 2019-07-12 12:24:03 -07:00
net netfilter: nfnetlink: avoid deadlock due to synchronous request_module 2019-07-15 07:56:58 +02:00
samples Kbuild updates for v5.3 2019-07-12 16:03:16 -07:00
scripts powerpc updates for 5.3 2019-07-13 16:08:36 -07:00
security Merge branch 'akpm' (patches from Andrew) 2019-07-12 11:40:28 -07:00
sound Driver Core and debugfs changes for 5.3-rc1 2019-07-12 12:24:03 -07:00
tools powerpc updates for 5.3 2019-07-13 16:08:36 -07:00
usr kbuild: compile-test exported headers to ensure they are self-contained 2019-07-08 23:13:57 +09:00
virt ARM: 2019-07-12 15:35:14 -07:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore kbuild: do not create wrappers for header-test-y 2019-07-09 10:10:27 +09:00
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS This pull-request contains the following changes for MTD: 2019-07-13 15:42:44 -07:00
Makefile Kbuild updates for v5.3 2019-07-12 16:03:16 -07:00
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.