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Chieh-Min Wang 3a1ce97938 netfilter: conntrack: fix cloned unconfirmed skb->_nfct race in __nf_conntrack_confirm [ Upstream commit `13f5251fd1` ] For bridge(br_flood) or broadcast/multicast packets, they could clone skb with unconfirmed conntrack which break the rule that unconfirmed skb->_nfct is never shared. With nfqueue running on my system, the race can be easily reproduced with following warning calltrace: [13257.707525] CPU: 0 PID: 12132 Comm: main Tainted: P W 4.4.60 #7744 [13257.707568] Hardware name: Qualcomm (Flattened Device Tree) [13257.714700] [<c021f6dc>] (unwind_backtrace) from [<c021bce8>] (show_stack+0x10/0x14) [13257.720253] [<c021bce8>] (show_stack) from [<c0449e10>] (dump_stack+0x94/0xa8) [13257.728240] [<c0449e10>] (dump_stack) from [<c022a7e0>] (warn_slowpath_common+0x94/0xb0) [13257.735268] [<c022a7e0>] (warn_slowpath_common) from [<c022a898>] (warn_slowpath_null+0x1c/0x24) [13257.743519] [<c022a898>] (warn_slowpath_null) from [<c06ee450>] (__nf_conntrack_confirm+0xa8/0x618) [13257.752284] [<c06ee450>] (__nf_conntrack_confirm) from [<c0772670>] (ipv4_confirm+0xb8/0xfc) [13257.761049] [<c0772670>] (ipv4_confirm) from [<c06e7a60>] (nf_iterate+0x48/0xa8) [13257.769725] [<c06e7a60>] (nf_iterate) from [<c06e7af0>] (nf_hook_slow+0x30/0xb0) [13257.777108] [<c06e7af0>] (nf_hook_slow) from [<c07f20b4>] (br_nf_post_routing+0x274/0x31c) [13257.784486] [<c07f20b4>] (br_nf_post_routing) from [<c06e7a60>] (nf_iterate+0x48/0xa8) [13257.792556] [<c06e7a60>] (nf_iterate) from [<c06e7af0>] (nf_hook_slow+0x30/0xb0) [13257.800458] [<c06e7af0>] (nf_hook_slow) from [<c07e5580>] (br_forward_finish+0x94/0xa4) [13257.808010] [<c07e5580>] (br_forward_finish) from [<c07f22ac>] (br_nf_forward_finish+0x150/0x1ac) [13257.815736] [<c07f22ac>] (br_nf_forward_finish) from [<c06e8df0>] (nf_reinject+0x108/0x170) [13257.824762] [<c06e8df0>] (nf_reinject) from [<c06ea854>] (nfqnl_recv_verdict+0x3d8/0x420) [13257.832924] [<c06ea854>] (nfqnl_recv_verdict) from [<c06e940c>] (nfnetlink_rcv_msg+0x158/0x248) [13257.841256] [<c06e940c>] (nfnetlink_rcv_msg) from [<c06e5564>] (netlink_rcv_skb+0x54/0xb0) [13257.849762] [<c06e5564>] (netlink_rcv_skb) from [<c06e4ec8>] (netlink_unicast+0x148/0x23c) [13257.858093] [<c06e4ec8>] (netlink_unicast) from [<c06e5364>] (netlink_sendmsg+0x2ec/0x368) [13257.866348] [<c06e5364>] (netlink_sendmsg) from [<c069fb8c>] (sock_sendmsg+0x34/0x44) [13257.874590] [<c069fb8c>] (sock_sendmsg) from [<c06a03dc>] (___sys_sendmsg+0x1ec/0x200) [13257.882489] [<c06a03dc>] (___sys_sendmsg) from [<c06a11c8>] (__sys_sendmsg+0x3c/0x64) [13257.890300] [<c06a11c8>] (__sys_sendmsg) from [<c0209b40>] (ret_fast_syscall+0x0/0x34) The original code just triggered the warning but do nothing. It will caused the shared conntrack moves to the dying list and the packet be droppped (nf_ct_resolve_clash returns NF_DROP for dying conntrack). - Reproduce steps: +----------------------------+ \| br0(bridge) \| \| \| +-+---------+---------+------+ \| eth0\| \| eth1\| \| eth2\| \| \| \| \| \| \| +--+--+ +--+--+ +---+-+ \| \| \| \| \| \| +--+-+ +-+--+ +--+-+ \| PC1\| \| PC2\| \| PC3\| +----+ +----+ +----+ iptables -A FORWARD -m mark --mark 0x1000000/0x1000000 -j NFQUEUE --queue-num 100 --queue-bypass ps: Our nfq userspace program will set mark on packets whose connection has already been processed. PC1 sends broadcast packets simulated by hping3: hping3 --rand-source --udp 192.168.1.255 -i u100 - Broadcast racing flow chart is as follow: br_handle_frame BR_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, br_handle_frame_finish) // skb->_nfct (unconfirmed conntrack) is constructed at PRE_ROUTING stage br_handle_frame_finish // check if this packet is broadcast br_flood_forward br_flood list_for_each_entry_rcu(p, &br->port_list, list) // iterate through each port maybe_deliver deliver_clone skb = skb_clone(skb) __br_forward BR_HOOK(NFPROTO_BRIDGE, NF_BR_FORWARD,...) // queue in our nfq and received by our userspace program // goto __nf_conntrack_confirm with process context on CPU 1 br_pass_frame_up BR_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN,...) // goto __nf_conntrack_confirm with softirq context on CPU 0 Because conntrack confirm can happen at both INPUT and POSTROUTING stage. So with NFQUEUE running, skb->_nfct with the same unconfirmed conntrack could race on different core. This patch fixes a repeating kernel splat, now it is only displayed once. Signed-off-by: Chieh-Min Wang <chiehminw@synology.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		2019-04-05 22:33:08 +02:00
arch	powerpc/hugetlb: Handle mmap_min_addr correctly in get_unmapped_area callback	2019-04-05 22:33:02 +02:00
block	blk-mq: insert rq with DONTPREP to hctx dispatch list when requeue	2019-03-23 20:09:45 +01:00
certs	export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR()	2018-08-22 23:21:44 +09:00
crypto	crypto: testmgr - skip crc32c context test for ahash algorithms	2019-03-23 20:09:55 +01:00
Documentation	KVM: Reject device ioctls from processes other than the VM's creator	2019-04-03 06:26:29 +02:00
drivers	ACPI / video: Refactor and fix dmi_is_desktop()	2019-04-05 22:33:07 +02:00
firmware	kbuild: remove all dummy assignments to obj-	2017-11-18 11:46:06 +09:00
fs	jbd2: fix race when writing superblock	2019-04-05 22:33:07 +02:00
include	scsi: fcoe: make use of fip_mode enum complete	2019-04-05 22:33:04 +02:00
init	Revert "mm: use early_pfn_to_nid in page_ext_init"	2019-03-23 20:09:46 +01:00
ipc	ipc/shm.c: use ERR_CAST() for shm_lock() error return	2018-10-05 16:32:04 -07:00
kernel	kprobes: Prohibit probing on RCU debug routine	2019-04-05 22:33:08 +02:00
lib	kprobes: Prohibit probing on bsearch()	2019-04-05 22:33:08 +02:00
LICENSES	LICENSES: Remove CC-BY-SA-4.0 license text	2018-10-18 11:28:50 +02:00
mm	page_poison: play nicely with KASAN	2019-04-05 22:32:59 +02:00
net	netfilter: conntrack: fix cloned unconfirmed skb->_nfct race in __nf_conntrack_confirm	2019-04-05 22:33:08 +02:00
samples	samples: mei: use /dev/mei0 instead of /dev/mei	2019-02-15 08:10:11 +01:00
scripts	kbuild: modversions: Fix relative CRC byte order interpretation	2019-04-03 06:26:23 +02:00
security	security/selinux: fix SECURITY_LSM_NATIVE_LABELS on reused superblock	2019-03-23 20:10:06 +01:00
sound	SoC: imx-sgtl5000: add missing put_device()	2019-04-05 22:33:05 +02:00
tools	selftests: skip seccomp get_metadata test if not real root	2019-04-05 22:33:07 +02:00
usr	initramfs: move gen_initramfs_list.sh from scripts/ to usr/	2018-08-22 23:21:44 +09:00
virt	KVM: Reject device ioctls from processes other than the VM's creator	2019-04-03 06:26:29 +02:00
.clang-format	clang-format: Set IndentWrappedFunctionNames false	2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes	.gitattributes: set git diff driver for C source code files	2016-10-07 18:46:30 -07:00
.gitignore	Kbuild updates for v4.17 (2nd)	2018-04-15 17:21:30 -07:00
.mailmap	libnvdimm-for-4.19_misc	2018-08-25 18:13:10 -07:00
COPYING	COPYING: use the new text with points to the license files	2018-03-23 12:41:45 -06:00
CREDITS	9p: remove Ron Minnich from MAINTAINERS	2018-08-17 16:20:26 -07:00
Kbuild	Kbuild updates for v4.15	2017-11-17 17:45:29 -08:00
Kconfig	kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt	2018-08-02 08:06:55 +09:00
MAINTAINERS	MAINTAINERS: Add Sasha as a stable branch maintainer	2018-12-01 09:37:25 +01:00
Makefile	kbuild: invoke syncconfig if include/config/auto.conf.cmd is missing	2019-04-05 22:33:01 +02:00
README	Docs: Added a pointer to the formatted docs to README	2018-03-21 09:02:53 -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.
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.