CVE-2023-52438

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.

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.

Chih-Yen Chang discovered that the KSMBD implementation in the Linux kernel did not properly validate certain data structure fields when parsing lease contexts, leading to an out-of-bounds read vulnerability. A remote attacker could use this to cause a denial of service or possibly expose sensitive information. Quentin Minster discovered that a race condition existed in the KSMBD implementation in the Linux kernel, leading to a use-after-free vulnerability. A remote attacker could use this to cause a denial of service or possibly execute arbitrary code.