CVE-2024-26976
Estado: ModificadaAlta (7.8)—
Detalles técnicos trazas, registros y código del informe original
En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: KVM: siempre vacíe la cola de trabajo asíncrona #PF cuando se destruya la vCPU. Siempre vacíe la cola de trabajo asíncrona #PF por vCPU cuando una vCPU esté limpiando su cola de finalización, por ejemplo, cuando una VM y todo sus vCPU están siendo destruidas. KVM debe asegurarse de que ninguna de sus devoluciones de llamada de la cola de trabajo se esté ejecutando cuando se coloca la última referencia al _módulo_ KVM. Regalar una referencia a la VM asociada evita que la devolución de llamada de la cola de trabajo elimine la referencia a la memoria de vCPU/VM liberada, pero no evita que el módulo KVM se descargue antes de que se complete la devolución de llamada. Elimine el regalo de recuento de VM equivocado, ya que llamar a kvm_put_kvm() desde async_pf_execute() si kvm_put_kvm() vacía la cola de trabajo asíncrona #PF resultará en un punto muerto. async_pf_execute() no puede regresar hasta que finalice kvm_put_kvm(), y kvm_put_kvm() no puede regresar hasta que finalice async_pf_execute(): ADVERTENCIA: CPU: 8 PID: 251 en virt/kvm/kvm_main.c:1435 kvm_put_kvm+0x2d/0x320 [kvm] Módulos vinculados en: vhost_net vhost vhost_iotlb tap kvm_intel kvm irqbypass CPU: 8 PID: 251 Comm: kworker/8:1 Tainted: GW 6.6.0-rc1-e7af8d17224a-x86/gmem-vm #119 Nombre de hardware: Estándar QEMU PC (Q35 + ICH9, 2009), BIOS 0.0.0 06/02/2015 Cola de trabajo: eventos async_pf_execute [kvm] RIP: 0010:kvm_put_kvm+0x2d/0x320 [kvm] Seguimiento de llamadas: async_pf_execute+0x198/0x260 [kvm ] Process_one_work+0x145/0x2d0 work_thread+0x27e/0x3a0 kthread+0xba/0xe0 ret_from_fork+0x2d/0x50 ret_from_fork_asm+0x11/0x20 ---[ end trace 0000000000000000 ]--- INFORMACIÓN: tarea kworker /8:1: 251 bloqueado durante más de 120 segundos. Contaminado: GW 6.6.0-rc1-e7af8d17224a-x86/gmem-vm #119 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" desactiva este mensaje. tarea:kworker/8:1 estado:D pila:0 pid:251 ppid:2 banderas:0x00004000 Cola de trabajo: eventos async_pf_execute [kvm] Seguimiento de llamadas: __schedule+0x33f/0xa40 Schedule+0x53/0xc0 Schedule_timeout+0x12a/0x140 __wait_for_common+0x8d/0x1d0 __flush_work.isra.0+0x19f/0x2c0 kvm_clear_async_pf_completion_queue+0x129/0x190 [kvm] kvm_arch_destroy_vm+0x78/0x1b0 [kvm] x320 [kvm] async_pf_execute+0x198/0x260 [kvm] proceso_one_work+0x145/ 0x2d0 trabajador_thread+0x27e/0x3a0 kthread+0xba/0xe0 ret_from_fork+0x2d/0x50 ret_from_fork_asm+0x11/0x20 Si kvm_clear_async_pf_completion_queue() realmente vacía la cola de trabajo, entonces no hay necesidad de regalar un referencia porque todas las invocaciones de async_pf_execute () se verá obligado a completarse antes de que la vCPU y su VM sean destruidas o liberadas. Y eso, a su vez, corrige el error de descarga del módulo, ya que __fput() no ejecutará module_put() en la última referencia de vCPU hasta que se haya liberado la vCPU, por ejemplo, si al cerrar el archivo de vCPU también se coloca la última referencia al módulo KVM. Tenga en cuenta que kvm_check_async_pf_completion() también puede sacar el elemento de trabajo de la cola de finalización y, por lo tanto, también necesita vaciar la cola de trabajos, ya que kvm_clear_async_pf_completion_queue() no verá el trabajo. En teoría, esperar en la cola de trabajo podría retrasar una vCPU debido a la espera de que se complete el trabajo, pero esa es una posibilidad muy, muy pequeña y probablemente un retraso muy pequeño. kvm_arch_async_page_present_queued() realiza incondicionalmente una nueva solicitud, es decir, efectivamente retrasará la entrada del invitado, por lo que el trabajo restante es realmente solo: trace_kvm_async_pf_completed(addr, cr2_or_gpa); __kvm_vcpu_wake_up(vcpu); mmput(mm); y mmput() no puede eliminar la última referencia a las tablas de páginas si la vCPU aún está activa, es decir, la vCPU no se atascará al derribar las tablas de páginas. ---truncado---
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Puntuación base: 7.8
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.26%
- Percentil entre todas las CVEs puntuadas: 17
- Fecha de la puntuación: 8/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (2)
CWE
- CWE-400
Referencias
- https://git.kernel.org/stable/c/3d75b8aa5c29058a512db29da7cbee8052724157
- https://git.kernel.org/stable/c/4f3a3bce428fb439c66a578adc447afce7b4a750
- https://git.kernel.org/stable/c/82e25cc1c2e93c3023da98be282322fc08b61ffb
- https://git.kernel.org/stable/c/83d3c5e309611ef593e2fcb78444fc8ceedf9bac
- https://git.kernel.org/stable/c/a75afe480d4349c524d9c659b1a5a544dbc39a98
- https://git.kernel.org/stable/c/ab2c2f5d9576112ad22cfd3798071cb74693b1f5
- https://git.kernel.org/stable/c/b54478d20375874aeee257744dedfd3e413432ff
- https://git.kernel.org/stable/c/caa9af2e27c275e089d702cfbaaece3b42bca31b
- https://git.kernel.org/stable/c/f8730d6335e5f43d09151fca1f0f41922209a264
- https://git.kernel.org/stable/c/3d75b8aa5c29058a512db29da7cbee8052724157
- https://git.kernel.org/stable/c/4f3a3bce428fb439c66a578adc447afce7b4a750
- https://git.kernel.org/stable/c/82e25cc1c2e93c3023da98be282322fc08b61ffb
- https://git.kernel.org/stable/c/83d3c5e309611ef593e2fcb78444fc8ceedf9bac
- https://git.kernel.org/stable/c/a75afe480d4349c524d9c659b1a5a544dbc39a98
- https://git.kernel.org/stable/c/ab2c2f5d9576112ad22cfd3798071cb74693b1f5
- https://git.kernel.org/stable/c/b54478d20375874aeee257744dedfd3e413432ff
- https://git.kernel.org/stable/c/caa9af2e27c275e089d702cfbaaece3b42bca31b
- https://git.kernel.org/stable/c/f8730d6335e5f43d09151fca1f0f41922209a264
- https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html
- https://lists.debian.org/debian-lts-announce/2024/06/msg00020.html
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: Always flush async #PF workqueue when vCPU is being destroyed\n\nAlways flush the per-vCPU async #PF workqueue when a vCPU is clearing its\ncompletion queue, e.g. when a VM and all its vCPUs is being destroyed.\nKVM must ensure that none of its workqueue callbacks is running when the\nlast reference to the KVM _module_ is put. Gifting a reference to the\nassociated VM prevents the workqueue callback from dereferencing freed\nvCPU/VM memory, but does not prevent the KVM module from being unloaded\nbefore the callback completes.\n\nDrop the misguided VM refcount gifting, as calling kvm_put_kvm() from\nasync_pf_execute() if kvm_put_kvm() flushes the async #PF workqueue will\nresult in deadlock. async_pf_execute() can't return until kvm_put_kvm()\nfinishes, and kvm_put_kvm() can't return until async_pf_execute() finishes:\n\n WARNING: CPU: 8 PID: 251 at virt/kvm/kvm_main.c:1435 kvm_put_kvm+0x2d/0x320 [kvm]\n Modules linked in: vhost_net vhost vhost_iotlb tap kvm_intel kvm irqbypass\n CPU: 8 PID: 251 Comm: kworker/8:1 Tainted: G W 6.6.0-rc1-e7af8d17224a-x86/gmem-vm #119\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n Workqueue: events async_pf_execute [kvm]\n RIP: 0010:kvm_put_kvm+0x2d/0x320 [kvm]\n Call Trace:\n <TASK>\n async_pf_execute+0x198/0x260 [kvm]\n process_one_work+0x145/0x2d0\n worker_thread+0x27e/0x3a0\n kthread+0xba/0xe0\n ret_from_fork+0x2d/0x50\n ret_from_fork_asm+0x11/0x20\n </TASK>\n ---[ end trace 0000000000000000 ]---\n INFO: task kworker/8:1:251 blocked for more than 120 seconds.\n Tainted: G W 6.6.0-rc1-e7af8d17224a-x86/gmem-vm #119\n \"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\" disables this message.\n task:kworker/8:1 state:D stack:0 pid:251 ppid:2 flags:0x00004000\n Workqueue: events async_pf_execute [kvm]\n Call Trace:\n <TASK>\n __schedule+0x33f/0xa40\n schedule+0x53/0xc0\n schedule_timeout+0x12a/0x140\n __wait_for_common+0x8d/0x1d0\n __flush_work.isra.0+0x19f/0x2c0\n kvm_clear_async_pf_completion_queue+0x129/0x190 [kvm]\n kvm_arch_destroy_vm+0x78/0x1b0 [kvm]\n kvm_put_kvm+0x1c1/0x320 [kvm]\n async_pf_execute+0x198/0x260 [kvm]\n process_one_work+0x145/0x2d0\n worker_thread+0x27e/0x3a0\n kthread+0xba/0xe0\n ret_from_fork+0x2d/0x50\n ret_from_fork_asm+0x11/0x20\n </TASK>\n\nIf kvm_clear_async_pf_completion_queue() actually flushes the workqueue,\nthen there's no need to gift async_pf_execute() a reference because all\ninvocations of async_pf_execute() will be forced to complete before the\nvCPU and its VM are destroyed/freed. And that in turn fixes the module\nunloading bug as __fput() won't do module_put() on the last vCPU reference\nuntil the vCPU has been freed, e.g. if closing the vCPU file also puts the\nlast reference to the KVM module.\n\nNote that kvm_check_async_pf_completion() may also take the work item off\nthe completion queue and so also needs to flush the work queue, as the\nwork will not be seen by kvm_clear_async_pf_completion_queue(). Waiting\non the workqueue could theoretically delay a vCPU due to waiting for the\nwork to complete, but that's a very, very small chance, and likely a very\nsmall delay. kvm_arch_async_page_present_queued() unconditionally makes a\nnew request, i.e. will effectively delay entering the guest, so the\nremaining work is really just:\n\n trace_kvm_async_pf_completed(addr, cr2_or_gpa);\n\n __kvm_vcpu_wake_up(vcpu);\n\n mmput(mm);\n\nand mmput() can't drop the last reference to the page tables if the vCPU is\nstill alive, i.e. the vCPU won't get stuck tearing down page tables.\n\nAdd a helper to do the flushing, specifically to deal with \"wakeup all\"\nwork items, as they aren't actually work items, i.e. are never placed in a\nworkqueue. Trying to flush a bogus workqueue entry rightly makes\n__flush_work() complain (kudos to whoever added that sanity check).\n\nNote, commit 5f6de5cbebee (\"KVM: Prevent module exit until al\n---truncated---"
},
{
"lang": "es",
"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: KVM: siempre vacíe la cola de trabajo asíncrona #PF cuando se destruya la vCPU. Siempre vacíe la cola de trabajo asíncrona #PF por vCPU cuando una vCPU esté limpiando su cola de finalización, por ejemplo, cuando una VM y todo sus vCPU están siendo destruidas. KVM debe asegurarse de que ninguna de sus devoluciones de llamada de la cola de trabajo se esté ejecutando cuando se coloca la última referencia al _módulo_ KVM. Regalar una referencia a la VM asociada evita que la devolución de llamada de la cola de trabajo elimine la referencia a la memoria de vCPU/VM liberada, pero no evita que el módulo KVM se descargue antes de que se complete la devolución de llamada. Elimine el regalo de recuento de VM equivocado, ya que llamar a kvm_put_kvm() desde async_pf_execute() si kvm_put_kvm() vacía la cola de trabajo asíncrona #PF resultará en un punto muerto. async_pf_execute() no puede regresar hasta que finalice kvm_put_kvm(), y kvm_put_kvm() no puede regresar hasta que finalice async_pf_execute(): ADVERTENCIA: CPU: 8 PID: 251 en virt/kvm/kvm_main.c:1435 kvm_put_kvm+0x2d/0x320 [kvm] Módulos vinculados en: vhost_net vhost vhost_iotlb tap kvm_intel kvm irqbypass CPU: 8 PID: 251 Comm: kworker/8:1 Tainted: GW 6.6.0-rc1-e7af8d17224a-x86/gmem-vm #119 Nombre de hardware: Estándar QEMU PC (Q35 + ICH9, 2009), BIOS 0.0.0 06/02/2015 Cola de trabajo: eventos async_pf_execute [kvm] RIP: 0010:kvm_put_kvm+0x2d/0x320 [kvm] Seguimiento de llamadas: async_pf_execute+0x198/0x260 [kvm ] Process_one_work+0x145/0x2d0 work_thread+0x27e/0x3a0 kthread+0xba/0xe0 ret_from_fork+0x2d/0x50 ret_from_fork_asm+0x11/0x20 ---[ end trace 0000000000000000 ]--- INFORMACIÓN: tarea kworker /8:1: 251 bloqueado durante más de 120 segundos. Contaminado: GW 6.6.0-rc1-e7af8d17224a-x86/gmem-vm #119 \"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\" desactiva este mensaje. tarea:kworker/8:1 estado:D pila:0 pid:251 ppid:2 banderas:0x00004000 Cola de trabajo: eventos async_pf_execute [kvm] Seguimiento de llamadas: __schedule+0x33f/0xa40 Schedule+0x53/0xc0 Schedule_timeout+0x12a/0x140 __wait_for_common+0x8d/0x1d0 __flush_work.isra.0+0x19f/0x2c0 kvm_clear_async_pf_completion_queue+0x129/0x190 [kvm] kvm_arch_destroy_vm+0x78/0x1b0 [kvm] x320 [kvm] async_pf_execute+0x198/0x260 [kvm] proceso_one_work+0x145/ 0x2d0 trabajador_thread+0x27e/0x3a0 kthread+0xba/0xe0 ret_from_fork+0x2d/0x50 ret_from_fork_asm+0x11/0x20 Si kvm_clear_async_pf_completion_queue() realmente vacía la cola de trabajo, entonces no hay necesidad de regalar un referencia porque todas las invocaciones de async_pf_execute () se verá obligado a completarse antes de que la vCPU y su VM sean destruidas o liberadas. Y eso, a su vez, corrige el error de descarga del módulo, ya que __fput() no ejecutará module_put() en la última referencia de vCPU hasta que se haya liberado la vCPU, por ejemplo, si al cerrar el archivo de vCPU también se coloca la última referencia al módulo KVM. Tenga en cuenta que kvm_check_async_pf_completion() también puede sacar el elemento de trabajo de la cola de finalización y, por lo tanto, también necesita vaciar la cola de trabajos, ya que kvm_clear_async_pf_completion_queue() no verá el trabajo. En teoría, esperar en la cola de trabajo podría retrasar una vCPU debido a la espera de que se complete el trabajo, pero esa es una posibilidad muy, muy pequeña y probablemente un retraso muy pequeño. kvm_arch_async_page_present_queued() realiza incondicionalmente una nueva solicitud, es decir, efectivamente retrasará la entrada del invitado, por lo que el trabajo restante es realmente solo: trace_kvm_async_pf_completed(addr, cr2_or_gpa); __kvm_vcpu_wake_up(vcpu); mmput(mm); y mmput() no puede eliminar la última referencia a las tablas de páginas si la vCPU aún está activa, es decir, la vCPU no se atascará al derribar las tablas de páginas. ---truncado---"
}
],
"lastModified": "2026-08-04T11:17:30.040",
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