CVE-2024-40912 (Moderate severity, published 2024-07-11)
CVSS score: 4.7 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H)
CWE: CWE-833
Description: In the Linux kernel, the following vulnerability has been resolved:

wifi: mac80211: Fix deadlock in ieee80211_sta_ps_deliver_wakeup()

The ieee80211_sta_ps_deliver_wakeup() function takes sta->ps_lock to
synchronizes with ieee80211_tx_h_unicast_ps_buf() which is called from
softirq context. However using only spin_lock() to get sta->ps_lock in
ieee80211_sta_ps_deliver_wakeup() does not prevent softirq to execute
on this same CPU, to run ieee80211_tx_h_unicast_ps_buf() and try to
take this same lock ending in deadlock. Below is an example of rcu stall
that arises in such situation.

 rcu: INFO: rcu_sched self-detected stall on CPU
 rcu:    2-....: (42413413 ticks this GP) idle=b154/1/0x4000000000000000 softirq=1763/1765 fqs=21206996
 rcu:    (t=42586894 jiffies g=2057 q=362405 ncpus=4)
 CPU: 2 PID: 719 Comm: wpa_supplicant Tainted: G        W          6.4.0-02158-g1b062f552873 #742
 Hardware name: RPT (r1) (DT)
 pstate: 00000005 (nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
 pc : queued_spin_lock_slowpath+0x58/0x2d0
 lr : invoke_tx_handlers_early+0x5b4/0x5c0
 sp : ffff00001ef64660
 x29: ffff00001ef64660 x28: ffff000009bc1070 x27: ffff000009bc0ad8
 x26: ffff000009bc0900 x25: ffff00001ef647a8 x24: 0000000000000000
 x23: ffff000009bc0900 x22: ffff000009bc0900 x21: ffff00000ac0e000
 x20: ffff00000a279e00 x19: ffff00001ef646e8 x18: 0000000000000000
 x17: ffff800016468000 x16: ffff00001ef608c0 x15: 0010533c93f64f80
 x14: 0010395c9faa3946 x13: 0000000000000000 x12: 00000000fa83b2da
 x11: 000000012edeceea x10: ffff0000010fbe00 x9 : 0000000000895440
 x8 : 000000000010533c x7 : ffff00000ad8b740 x6 : ffff00000c350880
 x5 : 0000000000000007 x4 : 0000000000000001 x3 : 0000000000000000
 x2 : 0000000000000000 x1 : 0000000000000001 x0 : ffff00000ac0e0e8
 Call trace:
  queued_spin_lock_slowpath+0x58/0x2d0
  ieee80211_tx+0x80/0x12c
  ieee80211_tx_pending+0x110/0x278
  tasklet_action_common.constprop.0+0x10c/0x144
  tasklet_action+0x20/0x28
  _stext+0x11c/0x284
  ____do_softirq+0xc/0x14
  call_on_irq_stack+0x24/0x34
  do_softirq_own_stack+0x18/0x20
  do_softirq+0x74/0x7c
  __local_bh_enable_ip+0xa0/0xa4
  _ieee80211_wake_txqs+0x3b0/0x4b8
  __ieee80211_wake_queue+0x12c/0x168
  ieee80211_add_pending_skbs+0xec/0x138
  ieee80211_sta_ps_deliver_wakeup+0x2a4/0x480
  ieee80211_mps_sta_status_update.part.0+0xd8/0x11c
  ieee80211_mps_sta_status_update+0x18/0x24
  sta_apply_parameters+0x3bc/0x4c0
  ieee80211_change_station+0x1b8/0x2dc
  nl80211_set_station+0x444/0x49c
  genl_family_rcv_msg_doit.isra.0+0xa4/0xfc
  genl_rcv_msg+0x1b0/0x244
  netlink_rcv_skb+0x38/0x10c
  genl_rcv+0x34/0x48
  netlink_unicast+0x254/0x2bc
  netlink_sendmsg+0x190/0x3b4
  ____sys_sendmsg+0x1e8/0x218
  ___sys_sendmsg+0x68/0x8c
  __sys_sendmsg+0x44/0x84
  __arm64_sys_sendmsg+0x20/0x28
  do_el0_svc+0x6c/0xe8
  el0_svc+0x14/0x48
  el0t_64_sync_handler+0xb0/0xb4
  el0t_64_sync+0x14c/0x150

Using spin_lock_bh()/spin_unlock_bh() instead prevents softirq to raise
on the same CPU that is holding the lock.
Mitigation: 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.