Subject: CVE-2022-48876: wifi: mac80211: fix initialization of rx->link and rx->link_sta

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

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

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

wifi: mac80211: fix initialization of rx->link and rx->link_sta

There are some codepaths that do not initialize rx->link_sta properly. This
causes a crash in places which assume that rx->link_sta is valid if rx->sta
is valid.
One known instance is triggered by __ieee80211_rx_h_amsdu being called from
fast-rx. It results in a crash like this one:

 BUG: kernel NULL pointer dereference, address: 00000000000000a8
 #PF: supervisor write access in kernel mode
 #PF: error_code(0x0002) - not-present page PGD 0 P4D 0
 Oops: 0002 [#1] PREEMPT SMP PTI
 CPU: 1 PID: 506 Comm: mt76-usb-rx phy Tainted: G            E      6.1.0-debian64x+1.7 #3
 Hardware name: ZOTAC ZBOX-ID92/ZBOX-IQ01/ZBOX-ID92/ZBOX-IQ01, BIOS B220P007 05/21/2014
 RIP: 0010:ieee80211_deliver_skb+0x62/0x1f0 [mac80211]
 Code: 00 48 89 04 24 e8 9e a7 c3 df 89 c0 48 03 1c c5 a0 ea 39 a1 4c 01 6b 08 48 ff 03 48
       83 7d 28 00 74 11 48 8b 45 30 48 63 55 44 <48> 83 84 d0 a8 00 00 00 01 41 8b 86 c0
       11 00 00 8d 50 fd 83 fa 01
 RSP: 0018:ffff999040803b10 EFLAGS: 00010286
 RAX: 0000000000000000 RBX: ffffb9903f496480 RCX: 0000000000000000
 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
 RBP: ffff999040803ce0 R08: 0000000000000000 R09: 0000000000000000
 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8d21828ac900
 R13: 000000000000004a R14: ffff8d2198ed89c0 R15: ffff8d2198ed8000
 FS:  0000000000000000(0000) GS:ffff8d24afe80000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00000000000000a8 CR3: 0000000429810002 CR4: 00000000001706e0
 Call Trace:
  <TASK>
  __ieee80211_rx_h_amsdu+0x1b5/0x240 [mac80211]
  ? ieee80211_prepare_and_rx_handle+0xcdd/0x1320 [mac80211]
  ? __local_bh_enable_ip+0x3b/0xa0
  ieee80211_prepare_and_rx_handle+0xcdd/0x1320 [mac80211]
  ? prepare_transfer+0x109/0x1a0 [xhci_hcd]
  ieee80211_rx_list+0xa80/0xda0 [mac80211]
  mt76_rx_complete+0x207/0x2e0 [mt76]
  mt76_rx_poll_complete+0x357/0x5a0 [mt76]
  mt76u_rx_worker+0x4f5/0x600 [mt76_usb]
  ? mt76_get_min_avg_rssi+0x140/0x140 [mt76]
  __mt76_worker_fn+0x50/0x80 [mt76]
  kthread+0xed/0x120
  ? kthread_complete_and_exit+0x20/0x20
  ret_from_fork+0x22/0x30

Since the initialization of rx->link and rx->link_sta is rather convoluted
and duplicated in many places, clean it up by using a helper function to
set it.

[remove unnecessary rx->sta->sta.mlo check]

The Linux kernel CVE team has assigned CVE-2022-48876 to this issue.

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

	Issue introduced in 6.1 with commit b320d6c456ff and fixed in 6.1.8 with commit a57c981d9f24
	Issue introduced in 6.1 with commit b320d6c456ff and fixed in 6.2 with commit e66b7920aa5a

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-2022-48876
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/mac80211/rx.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/a57c981d9f24d2bd89eaa76dc477e8ca252e22e8
	https://git.kernel.org/stable/c/e66b7920aa5ac5b1a1997a454004ba9246a3c005