// For flags

CVE-2023-52438

binder: fix use-after-free in shinker's callback

Severity Score

7.8
*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:

binder: fix use-after-free in shinker's callback

The mmap read lock is used during the shrinker's callback, which means
that using alloc->vma pointer isn't safe as it can race with munmap().
As of commit dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in
munmap") the mmap lock is downgraded after the vma has been isolated.

I was able to reproduce this issue by manually adding some delays and
triggering page reclaiming through the shrinker's debug sysfs. The
following KASAN report confirms the UAF:

==================================================================
BUG: KASAN: slab-use-after-free in zap_page_range_single+0x470/0x4b8
Read of size 8 at addr ffff356ed50e50f0 by task bash/478

CPU: 1 PID: 478 Comm: bash Not tainted 6.6.0-rc5-00055-g1c8b86a3799f-dirty #70
Hardware name: linux,dummy-virt (DT)
Call trace:
zap_page_range_single+0x470/0x4b8
binder_alloc_free_page+0x608/0xadc
__list_lru_walk_one+0x130/0x3b0
list_lru_walk_node+0xc4/0x22c
binder_shrink_scan+0x108/0x1dc
shrinker_debugfs_scan_write+0x2b4/0x500
full_proxy_write+0xd4/0x140
vfs_write+0x1ac/0x758
ksys_write+0xf0/0x1dc
__arm64_sys_write+0x6c/0x9c

Allocated by task 492:
kmem_cache_alloc+0x130/0x368
vm_area_alloc+0x2c/0x190
mmap_region+0x258/0x18bc
do_mmap+0x694/0xa60
vm_mmap_pgoff+0x170/0x29c
ksys_mmap_pgoff+0x290/0x3a0
__arm64_sys_mmap+0xcc/0x144

Freed by task 491:
kmem_cache_free+0x17c/0x3c8
vm_area_free_rcu_cb+0x74/0x98
rcu_core+0xa38/0x26d4
rcu_core_si+0x10/0x1c
__do_softirq+0x2fc/0xd24

Last potentially related work creation:
__call_rcu_common.constprop.0+0x6c/0xba0
call_rcu+0x10/0x1c
vm_area_free+0x18/0x24
remove_vma+0xe4/0x118
do_vmi_align_munmap.isra.0+0x718/0xb5c
do_vmi_munmap+0xdc/0x1fc
__vm_munmap+0x10c/0x278
__arm64_sys_munmap+0x58/0x7c

Fix this issue by performing instead a vma_lookup() which will fail to
find the vma that was isolated before the mmap lock downgrade. Note that
this option has better performance than upgrading to a mmap write lock
which would increase contention. Plus, mmap_write_trylock() has been
recently removed anyway.

En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: binder: corrige el use-after-free en la devolución de llamada de shinker. El bloqueo de lectura mmap se usa durante la devolución de llamada de shrinker, lo que significa que usar el puntero alloc->vma no es seguro ya que puede ejecutarse con munmap(). A partir de el commit dd2283f2605e ("mm: mmap: zap páginas con lectura mmap_sem en munmap"), el bloqueo mmap se degrada después de que se ha aislado el vma. Pude reproducir este problema agregando manualmente algunos retrasos y activando la recuperación de páginas a través del sistema de depuración del reductor. El siguiente informe de KASAN confirma la UAF: =========================================== ======================== ERROR: KASAN: slab-use-after-free en zap_page_range_single+0x470/0x4b8 Lectura de tamaño 8 en la dirección ffff356ed50e50f0 por tarea bash/478 CPU: 1 PID: 478 Comm: bash No contaminado 6.6.0-rc5-00055-g1c8b86a3799f-dirty #70 Nombre de hardware: linux,dummy-virt (DT) Rastreo de llamadas: zap_page_range_single+0x470/0x4b8 binder_alloc_free_page+0x608/ 0xadc __list_lru_walk_one+0x130/0x3b0 list_lru_walk_node+0xc4/0x22c binder_shrink_scan+0x108/0x1dc encogimiento_debugfs_scan_write+0x2b4/0x500 full_proxy_write+0xd4/0x140 vfs_write+0x1ac/0x758 ksys_write+0xf0/0x1dc __arm64_sys_write+0x6c/0x9c Asignado por la tarea 492: kmem_cache_alloc+0x130/ 0x368 vm_area_alloc+0x2c/0x190 mmap_region+0x258/0x18bc do_mmap+0x694/0xa60 vm_mmap_pgoff+0x170/0x29c ksys_mmap_pgoff+0x290/0x3a0 __arm64_sys_mmap+0xcc/0x144 Liberado por tarea 491: kmem_cache_free+0x17c/0x3c8 vm_area_free_rcu_cb+0x74/0x98 rcu_core+0xa38/ 0x26d4 rcu_core_si+0x10/0x1c __do_softirq+0x2fc/0xd24 Última creación de trabajo potencialmente relacionado: __call_rcu_common.constprop.0+0x6c/0xba0 call_rcu+0x10/0x1c vm_area_free+0x18/0x24 remove_vma+0xe4/0x118 do_vmi _align_munmap.isra.0+0x718/0xb5c do_vmi_munmap+0xdc/0x1fc __vm_munmap+0x10c/0x278 __arm64_sys_munmap+0x58/0x7c Solucione este problema realizando en su lugar un vma_lookup() que no podrá encontrar el vma que estaba aislado antes de la degradación del bloqueo mmap. Tenga en cuenta que esta opción tiene un mejor rendimiento que actualizar a un bloqueo de escritura mmap, lo que aumentaría la contención. Además, mmap_write_trylock() se eliminó recientemente de todos modos.

*Credits: N/A
CVSS Scores
Attack Vector
Local
Attack Complexity
Low
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
  • 2024-02-20 CVE Reserved
  • 2024-02-20 CVE Published
  • 2024-03-16 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"
>= 4.20 < 5.4.268
Search vendor "Linux" for product "Linux Kernel" and version " >= 4.20 < 5.4.268"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 4.20 < 5.10.209
Search vendor "Linux" for product "Linux Kernel" and version " >= 4.20 < 5.10.209"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 4.20 < 5.15.148
Search vendor "Linux" for product "Linux Kernel" and version " >= 4.20 < 5.15.148"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 4.20 < 6.1.74
Search vendor "Linux" for product "Linux Kernel" and version " >= 4.20 < 6.1.74"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 4.20 < 6.6.13
Search vendor "Linux" for product "Linux Kernel" and version " >= 4.20 < 6.6.13"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 4.20 < 6.7.1
Search vendor "Linux" for product "Linux Kernel" and version " >= 4.20 < 6.7.1"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 4.20 < 6.8
Search vendor "Linux" for product "Linux Kernel" and version " >= 4.20 < 6.8"
en
Affected