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We receive an ACPI notification every time the VM Generation ID changes and use the new ID as fresh randomness added to the entropy pool. This commits emits a uevent every time we receive the ACPI notification, as a means to notify the user space that it now is in a new VM. Signed-off-by: Babis Chalios <bchalios@amazon.es> Reviewed-by: Alexander Graf <graf@amazon.com> Reviewed-by: Lennart Poettering <mzxreary@0pointer.de> Link: https://lore.kernel.org/r/20230531095119.11202-2-bchalios@amazon.es Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
103 lines
2.7 KiB
C
103 lines
2.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
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*
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* The "Virtual Machine Generation ID" is exposed via ACPI and changes when a
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* virtual machine forks or is cloned. This driver exists for shepherding that
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* information to random.c.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/acpi.h>
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#include <linux/random.h>
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ACPI_MODULE_NAME("vmgenid");
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enum { VMGENID_SIZE = 16 };
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struct vmgenid_state {
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u8 *next_id;
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u8 this_id[VMGENID_SIZE];
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};
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static int vmgenid_add(struct acpi_device *device)
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{
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struct acpi_buffer parsed = { ACPI_ALLOCATE_BUFFER };
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struct vmgenid_state *state;
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union acpi_object *obj;
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phys_addr_t phys_addr;
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acpi_status status;
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int ret = 0;
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state = devm_kmalloc(&device->dev, sizeof(*state), GFP_KERNEL);
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if (!state)
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return -ENOMEM;
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status = acpi_evaluate_object(device->handle, "ADDR", NULL, &parsed);
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if (ACPI_FAILURE(status)) {
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ACPI_EXCEPTION((AE_INFO, status, "Evaluating ADDR"));
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return -ENODEV;
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}
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obj = parsed.pointer;
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if (!obj || obj->type != ACPI_TYPE_PACKAGE || obj->package.count != 2 ||
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obj->package.elements[0].type != ACPI_TYPE_INTEGER ||
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obj->package.elements[1].type != ACPI_TYPE_INTEGER) {
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ret = -EINVAL;
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goto out;
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}
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phys_addr = (obj->package.elements[0].integer.value << 0) |
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(obj->package.elements[1].integer.value << 32);
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state->next_id = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB);
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if (IS_ERR(state->next_id)) {
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ret = PTR_ERR(state->next_id);
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goto out;
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}
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memcpy(state->this_id, state->next_id, sizeof(state->this_id));
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add_device_randomness(state->this_id, sizeof(state->this_id));
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device->driver_data = state;
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out:
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ACPI_FREE(parsed.pointer);
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return ret;
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}
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static void vmgenid_notify(struct acpi_device *device, u32 event)
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{
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struct vmgenid_state *state = acpi_driver_data(device);
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char *envp[] = { "NEW_VMGENID=1", NULL };
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u8 old_id[VMGENID_SIZE];
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memcpy(old_id, state->this_id, sizeof(old_id));
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memcpy(state->this_id, state->next_id, sizeof(state->this_id));
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if (!memcmp(old_id, state->this_id, sizeof(old_id)))
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return;
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add_vmfork_randomness(state->this_id, sizeof(state->this_id));
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kobject_uevent_env(&device->dev.kobj, KOBJ_CHANGE, envp);
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}
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static const struct acpi_device_id vmgenid_ids[] = {
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{ "VMGENCTR", 0 },
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{ "VM_GEN_COUNTER", 0 },
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{ }
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};
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static struct acpi_driver vmgenid_driver = {
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.name = "vmgenid",
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.ids = vmgenid_ids,
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.owner = THIS_MODULE,
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.ops = {
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.add = vmgenid_add,
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.notify = vmgenid_notify
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}
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};
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module_acpi_driver(vmgenid_driver);
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MODULE_DEVICE_TABLE(acpi, vmgenid_ids);
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MODULE_DESCRIPTION("Virtual Machine Generation ID");
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MODULE_LICENSE("GPL v2");
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MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");
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