Subject: CVE-2022-48935: netfilter: nf_tables: unregister flowtable hooks on netns exit

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_tables: unregister flowtable hooks on netns exit

Unregister flowtable hooks before they are releases via
nf_tables_flowtable_destroy() otherwise hook core reports UAF.

BUG: KASAN: use-after-free in nf_hook_entries_grow+0x5a7/0x700 net/netfilter/core.c:142 net/netfilter/core.c:142
Read of size 4 at addr ffff8880736f7438 by task syz-executor579/3666

CPU: 0 PID: 3666 Comm: syz-executor579 Not tainted 5.16.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 __dump_stack lib/dump_stack.c:88 [inline] lib/dump_stack.c:106
 dump_stack_lvl+0x1dc/0x2d8 lib/dump_stack.c:106 lib/dump_stack.c:106
 print_address_description+0x65/0x380 mm/kasan/report.c:247 mm/kasan/report.c:247
 __kasan_report mm/kasan/report.c:433 [inline]
 __kasan_report mm/kasan/report.c:433 [inline] mm/kasan/report.c:450
 kasan_report+0x19a/0x1f0 mm/kasan/report.c:450 mm/kasan/report.c:450
 nf_hook_entries_grow+0x5a7/0x700 net/netfilter/core.c:142 net/netfilter/core.c:142
 __nf_register_net_hook+0x27e/0x8d0 net/netfilter/core.c:429 net/netfilter/core.c:429
 nf_register_net_hook+0xaa/0x180 net/netfilter/core.c:571 net/netfilter/core.c:571
 nft_register_flowtable_net_hooks+0x3c5/0x730 net/netfilter/nf_tables_api.c:7232 net/netfilter/nf_tables_api.c:7232
 nf_tables_newflowtable+0x2022/0x2cf0 net/netfilter/nf_tables_api.c:7430 net/netfilter/nf_tables_api.c:7430
 nfnetlink_rcv_batch net/netfilter/nfnetlink.c:513 [inline]
 nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]
 nfnetlink_rcv_batch net/netfilter/nfnetlink.c:513 [inline] net/netfilter/nfnetlink.c:652
 nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline] net/netfilter/nfnetlink.c:652
 nfnetlink_rcv+0x10e6/0x2550 net/netfilter/nfnetlink.c:652 net/netfilter/nfnetlink.c:652

__nft_release_hook() calls nft_unregister_flowtable_net_hooks() which
only unregisters the hooks, then after RCU grace period, it is
guaranteed that no packets add new entries to the flowtable (no flow
offload rules and flowtable hooks are reachable from packet path), so it
is safe to call nf_flow_table_free() which cleans up the remaining
entries from the flowtable (both software and hardware) and it unbinds
the flow_block.

The Linux kernel CVE team has assigned CVE-2022-48935 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.5 with commit ff4bf2f42a40 and fixed in 4.19.316 with commit 88c795491bf4
	Issue introduced in 5.5 with commit ff4bf2f42a40 and fixed in 5.4.262 with commit b05a24cc453e
	Issue introduced in 5.5 with commit ff4bf2f42a40 and fixed in 5.10.198 with commit e51f30826bc5
	Issue introduced in 5.5 with commit ff4bf2f42a40 and fixed in 5.15.26 with commit 8ffb8ac34488
	Issue introduced in 5.5 with commit ff4bf2f42a40 and fixed in 5.16.12 with commit b4fcc081e527
	Issue introduced in 5.5 with commit ff4bf2f42a40 and fixed in 5.17 with commit 6069da443bf6

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-48935
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	net/netfilter/nf_tables_api.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/88c795491bf45a8c08a0f94c9ca4f13722e51013
	https://git.kernel.org/stable/c/b05a24cc453e3cd51b0c79e3c583b5d495eba1d6
	https://git.kernel.org/stable/c/e51f30826bc5384801df98d76109c94953d1df64
	https://git.kernel.org/stable/c/8ffb8ac3448845f65634889b051bd65e4dee484b
	https://git.kernel.org/stable/c/b4fcc081e527aa2ce12e956912fc47e251f6bd27
	https://git.kernel.org/stable/c/6069da443bf65f513bb507bb21e2f87cfb1ad0b6