CVE-2024-26698

En el kernel de Linux, se resolvió la siguiente vulnerabilidad: hv_netvsc: corrige la condición de ejecución entre netvsc_probe y netvsc_remove En el commit ac5047671758 ("hv_netvsc: deshabilite NAPI antes de cerrar el canal VMBus"), se llamaba a napi_disable para todos los canales, incluidos todos los subcanales sin confirmando si están habilitados o no. Esto provocó que hv_netvsc se colgara en napi_disable, cuando netvsc_probe() terminó de ejecutarse pero nvdev->subchan_work aún no se inició. netvsc_subchan_work() -> rndis_set_subchannel() no ha creado los subcanales y por eso netvsc_sc_open() no se está ejecutando. netvsc_remove() llama a cancel_work_sync(&nvdev->subchan_work), para lo cual netvsc_subchan_work no se ejecutó. netif_napi_add() establece el bit NAPI_STATE_SCHED porque garantiza que NAPI no se pueda programar. Luego netvsc_sc_open() -> napi_enable borrará el bit NAPIF_STATE_SCHED, para que pueda programarse. napi_disable() hace lo contrario. Ahora, durante netvsc_device_remove(), cuando se llama a napi_disable para esos subcanales, napi_disable se atasca en msleep infinito. Esta solución soluciona este problema garantizando que no se llame a napi_disable() para una estructura NAPI no habilitada. Pero netif_napi_del() sigue siendo necesario para estas estructuras NAPI no habilitadas con fines de limpieza. Rastreo de llamadas: [654.559417] tarea:modprobe estado:D pila: 0 pid: 2321 ppid: 1091 banderas:0x00004002 [654.568030] Rastreo de llamadas: [654.571221] [654.573790] __schedule+0x2d6/0x960 [ 65 4.577733] horario+0x69 /0xf0 [654.581214] Schedule_timeout+0x87/0x140 [654.585463]? __bpf_trace_tick_stop+0x20/0x20 [ 654.590291] msleep+0x2d/0x40 [ 654.593625] napi_disable+0x2b/0x80 [ 654.597437] netvsc_device_remove+0x8a/0x1f0 [hv_netvsc] [ 6 54.603935] rndis_filter_device_remove+0x194/0x1c0 [hv_netvsc] [654.611101]? do_wait_intr+0xb0/0xb0 [ 654.615753] netvsc_remove+0x7c/0x120 [hv_netvsc] [ 654.621675] vmbus_remove+0x27/0x40 [hv_vmbus]

A vulnerability was found in the hv_netvsc driver in the Linux kernel, where a race condition is present between the netvsc_probe() and netvsc_remove() functions. This race condition could lead to system hangs during network device removal.

In the Linux kernel, the following vulnerability has been resolved: hv_netvsc: Fix race condition between netvsc_probe and netvsc_remove In commit ac5047671758 ("hv_netvsc: Disable NAPI before closing the VMBus channel"), napi_disable was getting called for all channels, including all subchannels without confirming if they are enabled or not. This caused hv_netvsc getting hung at napi_disable, when netvsc_probe() has finished running but nvdev->subchan_work has not started yet. netvsc_subchan_work() -> rndis_set_subchannel() has not created the sub-channels and because of that netvsc_sc_open() is not running. netvsc_remove() calls cancel_work_sync(&nvdev->subchan_work), for which netvsc_subchan_work did not run. netif_napi_add() sets the bit NAPI_STATE_SCHED because it ensures NAPI cannot be scheduled. Then netvsc_sc_open() -> napi_enable will clear the NAPIF_STATE_SCHED bit, so it can be scheduled. napi_disable() does the opposite. Now during netvsc_device_remove(), when napi_disable is called for those subchannels, napi_disable gets stuck on infinite msleep. This fix addresses this problem by ensuring that napi_disable() is not getting called for non-enabled NAPI struct. But netif_napi_del() is still necessary for these non-enabled NAPI struct for cleanup purpose. Call trace: [ 654.559417] task:modprobe state:D stack: 0 pid: 2321 ppid: 1091 flags:0x00004002 [ 654.568030] Call Trace: [ 654.571221] <TASK> [ 654.573790] __schedule+0x2d6/0x960 [ 654.577733] schedule+0x69/0xf0 [ 654.581214] schedule_timeout+0x87/0x140 [ 654.585463] ? __bpf_trace_tick_stop+0x20/0x20 [ 654.590291] msleep+0x2d/0x40 [ 654.593625] napi_disable+0x2b/0x80 [ 654.597437] netvsc_device_remove+0x8a/0x1f0 [hv_netvsc] [ 654.603935] rndis_filter_device_remove+0x194/0x1c0 [hv_netvsc] [ 654.611101] ? do_wait_intr+0xb0/0xb0 [ 654.615753] netvsc_remove+0x7c/0x120 [hv_netvsc] [ 654.621675] vmbus_remove+0x27/0x40 [hv_vmbus]