wifi: mac80211: fix initialization of rx-&gt;link and rx-&gt;link_sta
CVE: CVE-2022-48876
Component: kernel
CWE: CWE-476
Severity: Moderate
CVSS v3: 5.6/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Release date: 2022-01-01T00:00:00+00:00

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]

Statement: Following issue marked as moderate with "not affected" for Red Hat Enterprise Linux, as it is not vulnerable to this CVE. This is because the CVE does not impact the versions or configurations of the Linux kernel used in Red Hat's distributions. Additionally, some RHEL versions may be marked as "will not fix" due to the minimal impact of the issue, and no fix will be provided.

Remediation:
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.