// For flags

CVE-2023-52707

sched/psi: Fix use-after-free in ep_remove_wait_queue()

Severity Score

7.0
*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:

sched/psi: Fix use-after-free in ep_remove_wait_queue()

If a non-root cgroup gets removed when there is a thread that registered
trigger and is polling on a pressure file within the cgroup, the polling
waitqueue gets freed in the following path:

do_rmdir
cgroup_rmdir
kernfs_drain_open_files
cgroup_file_release
cgroup_pressure_release
psi_trigger_destroy

However, the polling thread still has a reference to the pressure file and
will access the freed waitqueue when the file is closed or upon exit:

fput
ep_eventpoll_release
ep_free
ep_remove_wait_queue
remove_wait_queue

This results in use-after-free as pasted below.

The fundamental problem here is that cgroup_file_release() (and
consequently waitqueue's lifetime) is not tied to the file's real lifetime.
Using wake_up_pollfree() here might be less than ideal, but it is in line
with the comment at commit 42288cb44c4b ("wait: add wake_up_pollfree()")
since the waitqueue's lifetime is not tied to file's one and can be
considered as another special case. While this would be fixable by somehow
making cgroup_file_release() be tied to the fput(), it would require
sizable refactoring at cgroups or higher layer which might be more
justifiable if we identify more cases like this.

BUG: KASAN: use-after-free in _raw_spin_lock_irqsave+0x60/0xc0
Write of size 4 at addr ffff88810e625328 by task a.out/4404

CPU: 19 PID: 4404 Comm: a.out Not tainted 6.2.0-rc6 #38
Hardware name: Amazon EC2 c5a.8xlarge/, BIOS 1.0 10/16/2017
Call Trace:
<TASK>
dump_stack_lvl+0x73/0xa0
print_report+0x16c/0x4e0
kasan_report+0xc3/0xf0
kasan_check_range+0x2d2/0x310
_raw_spin_lock_irqsave+0x60/0xc0
remove_wait_queue+0x1a/0xa0
ep_free+0x12c/0x170
ep_eventpoll_release+0x26/0x30
__fput+0x202/0x400
task_work_run+0x11d/0x170
do_exit+0x495/0x1130
do_group_exit+0x100/0x100
get_signal+0xd67/0xde0
arch_do_signal_or_restart+0x2a/0x2b0
exit_to_user_mode_prepare+0x94/0x100
syscall_exit_to_user_mode+0x20/0x40
do_syscall_64+0x52/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd
</TASK>

Allocated by task 4404:

kasan_set_track+0x3d/0x60
__kasan_kmalloc+0x85/0x90
psi_trigger_create+0x113/0x3e0
pressure_write+0x146/0x2e0
cgroup_file_write+0x11c/0x250
kernfs_fop_write_iter+0x186/0x220
vfs_write+0x3d8/0x5c0
ksys_write+0x90/0x110
do_syscall_64+0x43/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 4407:

kasan_set_track+0x3d/0x60
kasan_save_free_info+0x27/0x40
____kasan_slab_free+0x11d/0x170
slab_free_freelist_hook+0x87/0x150
__kmem_cache_free+0xcb/0x180
psi_trigger_destroy+0x2e8/0x310
cgroup_file_release+0x4f/0xb0
kernfs_drain_open_files+0x165/0x1f0
kernfs_drain+0x162/0x1a0
__kernfs_remove+0x1fb/0x310
kernfs_remove_by_name_ns+0x95/0xe0
cgroup_addrm_files+0x67f/0x700
cgroup_destroy_locked+0x283/0x3c0
cgroup_rmdir+0x29/0x100
kernfs_iop_rmdir+0xd1/0x140
vfs_rmdir+0xfe/0x240
do_rmdir+0x13d/0x280
__x64_sys_rmdir+0x2c/0x30
do_syscall_64+0x43/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd

En el kernel de Linux, se resolvió la siguiente vulnerabilidad: sched/psi: corrige el use after free en ep_remove_wait_queue() si se elimina un cgroup no raíz cuando hay un subproceso que registró un activador y está sondeando un archivo de presión dentro en cgroup, la cola de espera de sondeo se libera en la siguiente ruta: do_rmdir cgroup_rmdir kernfs_drain_open_files cgroup_file_release cgroup_pression_release psi_trigger_destroy Sin embargo, el hilo de sondeo aún tiene una referencia al archivo de presión y accederá a la cola de espera liberada cuando el archivo se cierre o al salir: fput ep_eventpoll_release ep_free ep_remove_wait_queue remove_wait_queue Esto da como resultado un use after free como se pega a continuación. El problema fundamental aquí es que cgroup_file_release() (y en consecuencia la vida útil de la cola de espera) no está ligada a la vida real del archivo. Usar wake_up_pollfree() aquí puede no ser ideal, pero está en línea con el comentario en la confirmación 42288cb44c4b ("espera: agregar wake_up_pollfree()") ya que la vida útil de la cola de espera no está ligada a la del archivo y puede considerarse como otro caso especial. . Si bien esto se podría solucionar haciendo que cgroup_file_release() esté vinculado de alguna manera a fput(), requeriría una refactorización considerable en cgroups o en una capa superior, lo que podría ser más justificable si identificamos más casos como este. ERROR: KASAN: use-after-free en _raw_spin_lock_irqsave+0x60/0xc0 Escritura de tamaño 4 en la dirección ffff88810e625328 por tarea a.out/4404 CPU: 19 PID: 4404 Comm: a.out No contaminado 6.2.0-rc6 #38 Hardware nombre: Amazon EC2 c5a.8xlarge/, BIOS 1.0 16/10/2017 Seguimiento de llamadas: dump_stack_lvl+0x73/0xa0 print_report+0x16c/0x4e0 kasan_report+0xc3/0xf0 kasan_check_range+0x2d2/0x310 _raw_spin_lock_irqsave+0x60/0x c0 remove_wait_queue+0x1a /0xa0 ep_free+0x12c/0x170 ep_eventpoll_release+0x26/0x30 __fput+0x202/0x400 task_work_run+0x11d/0x170 do_exit+0x495/0x1130 do_group_exit+0x100/0x100 get_signal+0xd67/0xde0 arch _do_signal_or_restart+0x2a/0x2b0 exit_to_user_mode_prepare+0x94/0x100 syscall_exit_to_user_mode+0x20 /0x40 do_syscall_64+0x52/0x90 Entry_SYSCALL_64_after_hwframe+0x63/0xcd Asignado por tarea 4404: kasan_set_track+0x3d/0x60 __kasan_kmalloc+0x85/0x90 psi_trigger_create+0x113/0x3e0 Pressure_write+0x1 46/0x2e0 cgroup_file_write+0x11c/0x250 kernfs_fop_write_iter+0x186/ 0x220 vfs_write+0x3d8/0x5c0 ksys_write+0x90/0x110 do_syscall_64+0x43/0x90 Entry_SYSCALL_64_after_hwframe+0x63/0xcd Liberado por la tarea 4407: kasan_set_track+0x3d/0x60 kasan_save_free_info+0x27/ 0x40 ____kasan_slab_free+0x11d/0x170 slab_free_freelist_hook+0x87/0x150 __kmem_cache_free+0xcb/ 0x180 psi_trigger_destroy+0x2e8/0x310 cgroup_file_release+0x4f/0xb0 kernfs_drain_open_files+0x165/0x1f0 kernfs_drain+0x162/0x1a0 __kernfs_remove+0x1fb/0x310 ns+0x95/0xe0 cgroup_addrm_files+0x67f/0x700 cgroup_destroy_locked+0x283/0x3c0 cgroup_rmdir+0x29/0x100 kernfs_iop_rmdir+0xd1/ 0x140 vfs_rmdir+0xfe/0x240 do_rmdir+0x13d/0x280 __x64_sys_rmdir+0x2c/0x30 do_syscall_64+0x43/0x90 Entry_SYSCALL_64_after_hwframe+0x63/0xcd

*Credits: N/A
CVSS Scores
Attack Vector
Local
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
* Common Vulnerability Scoring System
SSVC
  • Decision:Track
Exploitation
None
Automatable
No
Tech. Impact
Partial
* Organization's Worst-case Scenario
Timeline
  • 2024-03-07 CVE Reserved
  • 2024-05-21 CVE Published
  • 2024-05-22 EPSS Updated
  • 2024-12-19 CVE Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-416: Use After Free
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"
>= 5.2 < 5.4.232
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.2 < 5.4.232"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 5.2 < 5.10.169
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.2 < 5.10.169"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 5.2 < 5.15.95
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.2 < 5.15.95"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 5.2 < 6.1.13
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.2 < 6.1.13"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 5.2 < 6.2
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.2 < 6.2"
en
Affected