CVE-2024-26605

En el kernel de Linux, se resolvió la siguiente vulnerabilidad: PCI/ASPM: solucionó el punto muerto al habilitar ASPM. Una reversión de último minuto en 6.7-final introdujo un posible punto muerto al habilitar ASPM durante la prueba de los controladores PCIe de Qualcomm, según lo informado por lockdep: === ========================================= ADVERTENCIA: posible bloqueo recursivo detectado 6.7.0 #40 No contaminado -------------------------------------------- kworker/ u16:5/90 está intentando adquirir el bloqueo: ffffacfa78ced000 (pci_bus_sem){++++}-{3:3}, en: pcie_aspm_pm_state_change+0x58/0xdc pero la tarea ya mantiene el bloqueo: ffffacfa78ced000 (pci_bus_sem){+++ +}-{3:3}, en: pci_walk_bus+0x34/0xbc otra información que podría ayudarnos a depurar esto: Posible escenario de bloqueo inseguro: CPU0 ---- lock(pci_bus_sem); bloquear(pci_bus_sem); *** DEADLOCK *** Rastreo de llamadas: print_deadlock_bug+0x25c/0x348 __lock_acquire+0x10a4/0x2064 lock_acquire+0x1e8/0x318 down_read+0x60/0x184 pcie_aspm_pm_state_change+0x58/0xdc pci_set_full_power_state+0xa8/0x114 pci_ set_power_state+0xc4/0x120 qcom_pcie_enable_aspm+0x1c/0x3c [pcie_qcom] pci_walk_bus+0x64/0xbc qcom_pcie_host_post_init_2_7_0+0x28/0x34 [pcie_qcom] El punto muerto se puede reproducir fácilmente en máquinas como la Lenovo ThinkPad X13s agregando un retraso para aumentar la ventana de carrera durante la prueba asíncrona donde otro hilo puede tomar un bloqueo de escritura. Agregue un nuevo pci_set_power_state_locked() y funciones auxiliares asociadas que se pueden llamar con el semáforo del bus PCI retenido para evitar tomar el bloqueo de lectura dos veces.

A flaw was found in the Linux kernel, where a deadlock scenario was triggered when enabling Active State Power Management (ASPM) during the probe of Qualcomm PCIe controllers. This deadlock was identified by lockdep and stemmed from a recursive locking scenario. This issue occurred when a task attempted to acquire a lock already held by another task, leading to a deadlock situation. The deadlock could be reproduced on certain machines, such as the Lenovo ThinkPad X13s, by intentionally delaying operations to increase the race window during asynchronous probes, allowing another thread to take a write lock.

In the Linux kernel, the following vulnerability has been resolved: PCI/ASPM: Fix deadlock when enabling ASPM A last minute revert in 6.7-final introduced a potential deadlock when enabling ASPM during probe of Qualcomm PCIe controllers as reported by lockdep: ============================================ WARNING: possible recursive locking detected 6.7.0 #40 Not tainted -------------------------------------------- kworker/u16:5/90 is trying to acquire lock: ffffacfa78ced000 (pci_bus_sem){++++}-{3:3}, at: pcie_aspm_pm_state_change+0x58/0xdc but task is already holding lock: ffffacfa78ced000 (pci_bus_sem){++++}-{3:3}, at: pci_walk_bus+0x34/0xbc other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(pci_bus_sem); lock(pci_bus_sem); *** DEADLOCK *** Call trace: print_deadlock_bug+0x25c/0x348 __lock_acquire+0x10a4/0x2064 lock_acquire+0x1e8/0x318 down_read+0x60/0x184 pcie_aspm_pm_state_change+0x58/0xdc pci_set_full_power_state+0xa8/0x114 pci_set_power_state+0xc4/0x120 qcom_pcie_enable_aspm+0x1c/0x3c [pcie_qcom] pci_walk_bus+0x64/0xbc qcom_pcie_host_post_init_2_7_0+0x28/0x34 [pcie_qcom] The deadlock can easily be reproduced on machines like the Lenovo ThinkPad X13s by adding a delay to increase the race window during asynchronous probe where another thread can take a write lock. Add a new pci_set_power_state_locked() and associated helper functions that can be called with the PCI bus semaphore held to avoid taking the read lock twice.