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Vladimir Oltean 3f9e79f31e net: dsa: avoid suspicious RCU usage for synced VLAN-aware MAC addresses [ Upstream commit `d06f925f13` ] When using the felix driver (the only one which supports UC filtering and MC filtering) as a DSA master for a random other DSA switch, one can see the following stack trace when the downstream switch ports join a VLAN-aware bridge: ============================= WARNING: suspicious RCU usage ----------------------------- net/8021q/vlan_core.c:238 suspicious rcu_dereference_protected() usage! stack backtrace: Workqueue: dsa_ordered dsa_slave_switchdev_event_work Call trace: lockdep_rcu_suspicious+0x170/0x210 vlan_for_each+0x8c/0x188 dsa_slave_sync_uc+0x128/0x178 __hw_addr_sync_dev+0x138/0x158 dsa_slave_set_rx_mode+0x58/0x70 __dev_set_rx_mode+0x88/0xa8 dev_uc_add+0x74/0xa0 dsa_port_bridge_host_fdb_add+0xec/0x180 dsa_slave_switchdev_event_work+0x7c/0x1c8 process_one_work+0x290/0x568 What it's saying is that vlan_for_each() expects rtnl_lock() context and it's not getting it, when it's called from the DSA master's ndo_set_rx_mode(). The caller of that - dsa_slave_set_rx_mode() - is the slave DSA interface's dsa_port_bridge_host_fdb_add() which comes from the deferred dsa_slave_switchdev_event_work(). We went to great lengths to avoid the rtnl_lock() context in that call path in commit `0faf890fc5` ("net: dsa: drop rtnl_lock from dsa_slave_switchdev_event_work"), and calling rtnl_lock() is simply not an option due to the possibility of deadlocking when calling dsa_flush_workqueue() from the call paths that do hold rtnl_lock() - basically all of them. So, when the DSA master calls vlan_for_each() from its ndo_set_rx_mode(), the state of the 8021q driver on this device is really not protected from concurrent access by anything. Looking at net/8021q/, I don't think that vlan_info->vid_list was particularly designed with RCU traversal in mind, so introducing an RCU read-side form of vlan_for_each() - vlan_for_each_rcu() - won't be so easy, and it also wouldn't be exactly what we need anyway. In general I believe that the solution isn't in net/8021q/ anyway; vlan_for_each() is not cut out for this task. DSA doesn't need rtnl_lock() to be held per se - since it's not a netdev state change that we're blocking, but rather, just concurrent additions/removals to a VLAN list. We don't even need sleepable context - the callback of vlan_for_each() just schedules deferred work. The proposed escape is to remove the dependency on vlan_for_each() and to open-code a non-sleepable, rtnl-free alternative to that, based on copies of the VLAN list modified from .ndo_vlan_rx_add_vid() and .ndo_vlan_rx_kill_vid(). Fixes: `64fdc5f341` ("net: dsa: sync unicast and multicast addresses for VLAN filters too") Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Link: https://lore.kernel.org/r/20230626154402.3154454-1-vladimir.oltean@nxp.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		History 2023-07-19 16:35:37 +02:00
arch	watchdog/hardlockup: rename some "NMI watchdog" constants/function	2023-07-19 16:35:32 +02:00
block	blk-mq: don't insert passthrough request into sw queue	2023-07-19 16:35:14 +02:00
certs	KEYS: Add missing function documentation	2023-04-24 16:15:52 +03:00
crypto	KEYS: asymmetric: Copy sig and digest in public_key_verify_signature()	2023-06-02 15:36:23 +02:00
Documentation	dt-bindings: iio: ad7192: Add mandatory reference voltage source	2023-07-19 16:35:05 +02:00
drivers	ipvlan: Fix return value of ipvlan_queue_xmit()	2023-07-19 16:35:37 +02:00
fs	ocfs2: Fix use of slab data with sendpage	2023-07-19 16:35:36 +02:00
include	net: dsa: avoid suspicious RCU usage for synced VLAN-aware MAC addresses	2023-07-19 16:35:37 +02:00
init	start_kernel: Add __no_stack_protector function attribute	2023-07-19 16:35:05 +02:00
io_uring	io_uring/net: use the correct msghdr union member in io_sendmsg_copy_hdr	2023-06-21 07:34:17 -06:00
ipc	Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2023-02-24 19:20:07 -08:00
kernel	watchdog/hardlockup: keep kernel.nmi_watchdog sysctl as 0444 if probe fails	2023-07-19 16:35:33 +02:00
lib	lib/ts_bm: reset initial match offset for every block of text	2023-07-19 16:35:37 +02:00
LICENSES	LICENSES: Add the copyleft-next-0.3.1 license	2022-11-08 15:44:01 +01:00
mm	splice: Fix filemap_splice_read() to use the correct inode	2023-07-19 16:35:07 +02:00
net	net: dsa: avoid suspicious RCU usage for synced VLAN-aware MAC addresses	2023-07-19 16:35:37 +02:00
rust	Rust changes for v6.4	2023-04-30 11:20:22 -07:00
samples	samples/bpf: xdp1 and xdp2 reduce XDPBUFSIZE to 60	2023-07-19 16:35:25 +02:00
scripts	scripts/tags.sh: Resolve gtags empty index generation	2023-07-05 18:30:30 +01:00
security	ima: Fix build warnings	2023-07-19 16:35:20 +02:00
sound	ASoC: Fix for v6.4	2023-06-21 15:23:23 +02:00
tools	selftests: rtnetlink: remove netdevsim device after ipsec offload test	2023-07-19 16:35:36 +02:00
usr	initramfs: Check negative timestamp to prevent broken cpio archive	2023-04-16 17:37:01 +09:00
virt	KVM: Avoid illegal stage2 mapping on invalid memory slot	2023-06-22 15:14:57 -04:00
.clang-format	cxl for v6.4	2023-04-30 11:51:51 -07:00
.cocciconfig	scripts: add Linux .cocciconfig for coccinelle	2016-07-22 12:13:39 +02:00
.get_maintainer.ignore	get_maintainer: add Alan to .get_maintainer.ignore	2022-08-20 15:17:44 -07:00
.gitattributes	.gitattributes: use 'dts' diff driver for *.dtso files	2023-02-26 15:28:23 +09:00
.gitignore	linux-kselftest-kunit-6.4-rc1	2023-04-24 12:31:32 -07:00
.mailmap	mailmap: add entries for Ben Dooks	2023-06-19 13:19:35 -07:00
.rustfmt.toml	rust: add `.rustfmt.toml`	2022-09-28 09:02:20 +02:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: sctp: move Neil to CREDITS	2023-05-12 08:51:32 +01:00
Kbuild	Kbuild updates for v6.1	2022-10-10 12:00:45 -07:00
Kconfig	kbuild: ensure full rebuild when the compiler is updated	2020-05-12 13:28:33 +09:00
MAINTAINERS	Networking fixes for 6.4-rc8, including fixes from ipsec, bpf,	2023-06-22 17:59:51 -07:00
Makefile	Linux 6.4.3	2023-07-11 06:31:05 +02:00
README	Drop all 00-INDEX files from Documentation/	2018-09-09 15:08:58 -06:00

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.