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Vladimir Oltean d06f925f13 net: dsa: avoid suspicious RCU usage for synced VLAN-aware MAC addresses 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>		2023-06-27 09:37:41 -07:00
arch	Networking fixes for 6.4-rc8, including fixes from ipsec, bpf,	2023-06-22 17:59:51 -07:00
block	blk-cgroup: Flush stats before releasing blkcg_gq	2023-06-11 19:49:29 -06:00
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	Tracing fixes for 6.4:	2023-06-20 15:01:08 -07:00
drivers	net: usb: qmi_wwan: add u-blox 0x1312 composition	2023-06-27 15:52:15 +02:00
fs	19 hotfixes. 8 of these are cc:stable.	2023-06-20 17:20:22 -07:00
include	net: dsa: avoid suspicious RCU usage for synced VLAN-aware MAC addresses	2023-06-27 09:37:41 -07:00
init	Objtool changes for v6.4:	2023-04-28 14:02:54 -07:00
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	Networking fixes for 6.4-rc8, including fixes from ipsec, bpf,	2023-06-22 17:59:51 -07:00
lib	lib/ts_bm: reset initial match offset for every block of text	2023-06-26 13:26:39 +02:00
LICENSES	LICENSES: Add the copyleft-next-0.3.1 license	2022-11-08 15:44:01 +01:00
mm	19 hotfixes. 8 of these are cc:stable.	2023-06-20 17:20:22 -07:00
net	net: dsa: avoid suspicious RCU usage for synced VLAN-aware MAC addresses	2023-06-27 09:37:41 -07:00
rust	Rust changes for v6.4	2023-04-30 11:20:22 -07:00
samples	samples/bpf: Drop unnecessary fallthrough	2023-05-16 19:44:05 +02:00
scripts	scripts/gdb: fix SB_* constants parsing	2023-06-19 13:19:32 -07:00
security	selinux: don't use make's grouped targets feature yet	2023-06-01 13:56:13 -04:00
sound	ASoC: Fixes for v6.4	2023-06-16 09:28:27 +02:00
tools	selftests: rtnetlink: remove netdevsim device after ipsec offload test	2023-06-24 15:19:39 -07:00
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
.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	MAINTAINERS: update email addresses of octeon_ep driver maintainers	2023-06-22 19:27:39 -07:00
Makefile	Linux 6.4-rc7	2023-06-18 14:06:27 -07:00
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.