// For flags

CVE-2024-36888

workqueue: Fix selection of wake_cpu in kick_pool()

Severity Score

6.2
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

Track
*SSVC
Descriptions

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

workqueue: Fix selection of wake_cpu in kick_pool()

With cpu_possible_mask=0-63 and cpu_online_mask=0-7 the following
kernel oops was observed:

smp: Bringing up secondary CPUs ...
smp: Brought up 1 node, 8 CPUs
Unable to handle kernel pointer dereference in virtual kernel address space
Failing address: 0000000000000000 TEID: 0000000000000803
[..]
Call Trace:
arch_vcpu_is_preempted+0x12/0x80
select_idle_sibling+0x42/0x560
select_task_rq_fair+0x29a/0x3b0
try_to_wake_up+0x38e/0x6e0
kick_pool+0xa4/0x198
__queue_work.part.0+0x2bc/0x3a8
call_timer_fn+0x36/0x160
__run_timers+0x1e2/0x328
__run_timer_base+0x5a/0x88
run_timer_softirq+0x40/0x78
__do_softirq+0x118/0x388
irq_exit_rcu+0xc0/0xd8
do_ext_irq+0xae/0x168
ext_int_handler+0xbe/0xf0
psw_idle_exit+0x0/0xc
default_idle_call+0x3c/0x110
do_idle+0xd4/0x158
cpu_startup_entry+0x40/0x48
rest_init+0xc6/0xc8
start_kernel+0x3c4/0x5e0
startup_continue+0x3c/0x50

The crash is caused by calling arch_vcpu_is_preempted() for an offline
CPU. To avoid this, select the cpu with cpumask_any_and_distribute()
to mask __pod_cpumask with cpu_online_mask. In case no cpu is left in
the pool, skip the assignment.

tj: This doesn't fully fix the bug as CPUs can still go down between picking
the target CPU and the wake call. Fixing that likely requires adding
cpu_online() test to either the sched or s390 arch code. However, regardless
of how that is fixed, workqueue shouldn't be picking a CPU which isn't
online as that would result in unpredictable and worse behavior.

En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: workqueue: Se corrigió la selección de wake_cpu en kick_pool() Con cpu_possible_mask=0-63 y cpu_online_mask=0-7 se observaron los siguientes errores del kernel: smp: Apareciendo CPU secundarias... smp: abrió 1 nodo, 8 CPU No se puede manejar la desreferencia del puntero del kernel en el espacio de direcciones virtual del kernel Dirección fallida: 0000000000000000 TEID: 0000000000000803 [..] Seguimiento de llamadas: arch_vcpu_is_preempted+0x12/0x80 select_idle_sibling+0x42/0x560 _rq_fair+0x29a/0x3b0 intenta_despertar_up +0x38e/0x6e0 kick_pool+0xa4/0x198 __queue_work.part.0+0x2bc/0x3a8 call_timer_fn+0x36/0x160 __run_timers+0x1e2/0x328 __run_timer_base+0x5a/0x88 run_timer_softirq+0x40/0x78 irq+0x118/0x388 irq_exit_rcu+0xc0/0xd8 hacer_ext_irq+ 0xae/0x168 ext_int_handler+0xbe/0xf0 psw_idle_exit+0x0/0xc default_idle_call+0x3c/0x110 do_idle+0xd4/0x158 cpu_startup_entry+0x40/0x48 rest_init+0xc6/0xc8 startup_continue+0x3c/0x50 El bloqueo se produce al llamar a arch_vcpu_is_preempted () para una CPU fuera de línea. Para evitar esto, seleccione la CPU con cpumask_any_and_distribute() para enmascarar __pod_cpumask con cpu_online_mask. En caso de que no quede ninguna CPU en el grupo, omita la tarea. tj: Esto no soluciona completamente el error ya que las CPU aún pueden fallar entre la selección de la CPU de destino y la llamada de activación. Para solucionarlo, es probable que sea necesario agregar la prueba cpu_online() al código arch sched o s390. Sin embargo, independientemente de cómo se solucione, workqueue no debería elegir una CPU que no esté en línea, ya que eso resultaría en un comportamiento peor e impredecible.

*Credits: N/A
CVSS Scores
Attack Vector
Local
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
* Common Vulnerability Scoring System
SSVC
  • Decision:Track
Exploitation
None
Automatable
No
Tech. Impact
Partial
* Organization's Worst-case Scenario
Timeline
  • 2024-05-30 CVE Reserved
  • 2024-05-30 CVE Published
  • 2024-05-31 EPSS Updated
  • 2024-12-19 CVE Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-476: NULL Pointer Dereference
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 6.6 < 6.6.31
Search vendor "Linux" for product "Linux Kernel" and version " >= 6.6 < 6.6.31"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 6.6 < 6.8.10
Search vendor "Linux" for product "Linux Kernel" and version " >= 6.6 < 6.8.10"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 6.6 < 6.9
Search vendor "Linux" for product "Linux Kernel" and version " >= 6.6 < 6.9"
en
Affected