On 2017-12-18 02:06 PM, Adalber Lazăr wrote:
From: Adalbert Lazar <alazar@xxxxxxxxxxxxxxx>
An introspection tool running in a dedicated VM can use the new device
(/dev/kvmmem) to map memory from other introspected VM-s.
Two ioctl operations are supported:
- KVM_INTRO_MEM_MAP/struct kvmi_mem_map
- KVM_INTRO_MEM_UNMAP/unsigned long
In order to map an introspected gpa to the local gva, the process using
this device needs to obtain a token from the host KVMI subsystem (see
Documentation/virtual/kvm/kvmi.rst - KVMI_GET_MAP_TOKEN).
Both operations use hypercalls (KVM_HC_MEM_MAP, KVM_INTRO_MEM_UNMAP)
to pass the requests to the host kernel/KVMi (see hypercalls.txt).
Signed-off-by: Mircea Cîrjaliu <mcirjaliu@xxxxxxxxxxxxxxx>
---
arch/x86/Kconfig | 9 +
arch/x86/include/asm/kvmi_guest.h | 10 +
arch/x86/kernel/Makefile | 1 +
arch/x86/kernel/kvmi_mem_guest.c | 26 +++
virt/kvm/kvmi_mem_guest.c | 379 ++++++++++++++++++++++++++++++++++++++
5 files changed, 425 insertions(+)
create mode 100644 arch/x86/include/asm/kvmi_guest.h
create mode 100644 arch/x86/kernel/kvmi_mem_guest.c
create mode 100644 virt/kvm/kvmi_mem_guest.c
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 8eed3f94bfc7..6e2548f4d44c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -782,6 +782,15 @@ config KVM_DEBUG_FS
Statistics are displayed in debugfs filesystem. Enabling this option
may incur significant overhead.
+config KVMI_MEM_GUEST
+ bool "KVM Memory Introspection support on Guest"
+ depends on KVM_GUEST
+ default n
+ ---help---
+ This option enables functions and hypercalls for security applications
+ running in a separate VM to control the execution of other VM-s, query
+ the state of the vCPU-s (GPR-s, MSR-s etc.).
+
config PARAVIRT_TIME_ACCOUNTING
bool "Paravirtual steal time accounting"
depends on PARAVIRT
diff --git a/arch/x86/include/asm/kvmi_guest.h b/arch/x86/include/asm/kvmi_guest.h
new file mode 100644
index 000000000000..c7ed53a938e0
--- /dev/null
+++ b/arch/x86/include/asm/kvmi_guest.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __KVMI_GUEST_H__
+#define __KVMI_GUEST_H__
+
+long kvmi_arch_map_hc(struct kvmi_map_mem_token *tknp,
+ gpa_t req_gpa, gpa_t map_gpa);
+long kvmi_arch_unmap_hc(gpa_t map_gpa);
+
+
+#endif
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 81bb565f4497..fdb54b65e46e 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -111,6 +111,7 @@ obj-$(CONFIG_PARAVIRT) += paravirt.o paravirt_patch_$(BITS).o
obj-$(CONFIG_PARAVIRT_SPINLOCKS)+= paravirt-spinlocks.o
obj-$(CONFIG_PARAVIRT_CLOCK) += pvclock.o
obj-$(CONFIG_X86_PMEM_LEGACY_DEVICE) += pmem.o
+obj-$(CONFIG_KVMI_MEM_GUEST) += kvmi_mem_guest.o ../../../virt/kvm/kvmi_mem_guest.o
obj-$(CONFIG_EISA) += eisa.o
obj-$(CONFIG_PCSPKR_PLATFORM) += pcspeaker.o
diff --git a/arch/x86/kernel/kvmi_mem_guest.c b/arch/x86/kernel/kvmi_mem_guest.c
new file mode 100644
index 000000000000..c4e2613f90f3
--- /dev/null
+++ b/arch/x86/kernel/kvmi_mem_guest.c
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KVM introspection guest implementation
+ *
+ * Copyright (C) 2017 Bitdefender S.R.L.
+ *
+ * Author:
+ * Mircea Cirjaliu <mcirjaliu@xxxxxxxxxxxxxxx>
+ */
+
+#include <uapi/linux/kvmi.h>
+#include <uapi/linux/kvm_para.h>
+#include <linux/kvm_types.h>
+#include <asm/kvm_para.h>
+
+long kvmi_arch_map_hc(struct kvmi_map_mem_token *tknp,
+ gpa_t req_gpa, gpa_t map_gpa)
+{
+ return kvm_hypercall3(KVM_HC_MEM_MAP, (unsigned long)tknp,
+ req_gpa, map_gpa);
+}
+
+long kvmi_arch_unmap_hc(gpa_t map_gpa)
+{
+ return kvm_hypercall1(KVM_HC_MEM_UNMAP, map_gpa);
+}
diff --git a/virt/kvm/kvmi_mem_guest.c b/virt/kvm/kvmi_mem_guest.c
new file mode 100644
index 000000000000..118c22ca47c5
--- /dev/null
+++ b/virt/kvm/kvmi_mem_guest.c
@@ -0,0 +1,379 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KVM introspection guest implementation
+ *
+ * Copyright (C) 2017 Bitdefender S.R.L.
+ *
+ * Author:
+ * Mircea Cirjaliu <mcirjaliu@xxxxxxxxxxxxxxx>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/miscdevice.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/types.h>
+#include <linux/kvm_host.h>
+#include <linux/kvm_para.h>
+#include <linux/uaccess.h>
+#include <linux/slab.h>
+#include <linux/rmap.h>
+#include <linux/sched.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/mutex.h>
+#include <uapi/linux/kvmi.h>
+#include <asm/kvmi_guest.h>
+
+#define ASSERT(exp) BUG_ON(!(exp))
+
+
+static struct list_head file_list;
+static spinlock_t file_lock;
+
+struct file_map {
+ struct list_head file_list;
+ struct file *file;
+ struct list_head map_list;
+ struct mutex lock;
+ int active; /* for tearing down */
+};
+
+struct page_map {
+ struct list_head map_list;
+ __u64 gpa;
+ unsigned long vaddr;
+ unsigned long paddr;
+};
+
+
+static int kvm_dev_open(struct inode *inodep, struct file *filp)
+{
+ struct file_map *fmp;
+
+ pr_debug("kvmi: file %016lx opened by process %s\n",
+ (unsigned long) filp, current->comm);
+
+ /* link the file 1:1 with such a structure */
+ fmp = kmalloc(sizeof(struct file_map), GFP_KERNEL);
I think this is supposed to be "kmalloc(sizeof(*fmp), GFP_KERNEL)".
+ if (fmp == NULL)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&fmp->file_list);
+ fmp->file = filp;
+ filp->private_data = fmp;
+ INIT_LIST_HEAD(&fmp->map_list);
+ mutex_init(&fmp->lock);
+ fmp->active = 1;
+
+ /* add the entry to the global list */
+ spin_lock(&file_lock);
+ list_add_tail(&fmp->file_list, &file_list);
+ spin_unlock(&file_lock);
+
+ return 0;
+}
+
+/* actually does the mapping of a page */
+static long _do_mapping(struct kvmi_mem_map *map_req, struct page_map *pmap)
Here you have a "struct page_map" and call it pmap. However, in the rest
of the code, whenever there's a "struct page_map" it's called pmp. It
seems that it would be good to stay consistent with the naming, so
perhaps rename it here to pmp as well?
+{
+ unsigned long paddr;
+ struct vm_area_struct *vma = NULL; > + struct page *page;
Out of curiosity, why do you set "*vma = NULL" but not "*page = NULL"?
+ long result;
+
+ pr_debug("kvmi: mapping remote GPA %016llx into %016llx\n",
+ map_req->gpa, map_req->gva);
+
+ /* check access to memory location */
+ if (!access_ok(VERIFY_READ, map_req->gva, PAGE_SIZE)) {
+ pr_err("kvmi: invalid virtual address for mapping\n");
+ return -EINVAL;
+ }
+
+ down_read(¤t->mm->mmap_sem);
+
+ /* find the page to be replaced */
+ vma = find_vma(current->mm, map_req->gva);
+ if (IS_ERR_OR_NULL(vma)) {
+ result = PTR_ERR(vma);
+ pr_err("kvmi: find_vma() failed with result %ld\n", result);
+ goto out;
+ }
+
+ page = follow_page(vma, map_req->gva, 0);
+ if (IS_ERR_OR_NULL(page)) {
+ result = PTR_ERR(page);
+ pr_err("kvmi: follow_page() failed with result %ld\n", result);
+ goto out;
+ }
+
+ if (IS_ENABLED(CONFIG_DEBUG_VM))
+ dump_page(page, "page to map_req into");
+
+ WARN(is_zero_pfn(page_to_pfn(page)), "zero-page still mapped");
+
+ /* get the physical address and store it in page_map */
+ paddr = page_to_phys(page);
+ pr_debug("kvmi: page phys addr %016lx\n", paddr);
+ pmap->paddr = paddr;
+
+ /* last thing to do is host mapping */
+ result = kvmi_arch_map_hc(&map_req->token, map_req->gpa, paddr);
+ if (IS_ERR_VALUE(result)) {
+ pr_err("kvmi: HC failed with result %ld\n", result);
+ goto out;
+ }
+
+out:
+ up_read(¤t->mm->mmap_sem);
+
+ return result;
+}
+
+/* actually does the unmapping of a page */
+static long _do_unmapping(unsigned long paddr)
+{
+ long result;
+
+ pr_debug("kvmi: unmapping request for phys addr %016lx\n", paddr);
+
+ /* local GPA uniquely identifies the mapping on the host */
+ result = kvmi_arch_unmap_hc(paddr);
+ if (IS_ERR_VALUE(result))
+ pr_warn("kvmi: HC failed with result %ld\n", result);
+
+ return result;
+}
+
+static long kvm_dev_ioctl_map(struct file_map *fmp, struct kvmi_mem_map *map)
+{
+ struct page_map *pmp;
+ long result = 0;
Out of curiosity again, why do you set "result = 0" here when it's
always set before used (and, for e.g., _do_unmapping() doesn't do
"result = 0")?
+
+ if (!access_ok(VERIFY_READ, map->gva, PAGE_SIZE))
+ return -EINVAL;
+ if (!access_ok(VERIFY_WRITE, map->gva, PAGE_SIZE))
+ return -EINVAL;
+
+ /* prepare list entry */
+ pmp = kmalloc(sizeof(struct page_map), GFP_KERNEL);
This should also probably be "kmalloc(sizeof(*pmp), GFP_KERNEL)".
+ if (pmp == NULL)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&pmp->map_list);
+ pmp->gpa = map->gpa;
+ pmp->vaddr = map->gva;
+
+ /* acquire the file mapping */
+ mutex_lock(&fmp->lock);
+
+ /* check if other thread is closing the file */
+ if (!fmp->active) {
+ result = -ENODEV;
+ pr_warn("kvmi: unable to map, file is being closed\n");
+ goto out_err;
+ }
+
+ /* do the actual mapping */
+ result = _do_mapping(map, pmp);
+ if (IS_ERR_VALUE(result))
+ goto out_err;
+
+ /* link to list */
+ list_add_tail(&pmp->map_list, &fmp->map_list);
+
+ /* all fine */
+ result = 0;
+ goto out_finalize;
+
+out_err:
+ kfree(pmp);
+
+out_finalize:
+ mutex_unlock(&fmp->lock);
+
+ return result;
+}
+
+static long kvm_dev_ioctl_unmap(struct file_map *fmp, unsigned long vaddr)
+{
+ struct list_head *cur;
+ struct page_map *pmp;
+ bool found = false;
+
+ /* acquire the file */
+ mutex_lock(&fmp->lock);
+
+ /* check if other thread is closing the file */
+ if (!fmp->active) {
+ mutex_unlock(&fmp->lock);
Wouldn't this be better replaced with a "goto out_err" like in
kvm_dev_ioctl_map()?
+ pr_warn("kvmi: unable to unmap, file is being closed\n");
+ return -ENODEV;
+ }
+
+ /* check that this address belongs to us */
+ list_for_each(cur, &fmp->map_list) {
+ pmp = list_entry(cur, struct page_map, map_list);
+
+ /* found */
+ if (pmp->vaddr == vaddr) {
+ found = true;
+ break;
+ }
+ }
+
+ /* not found ? */
+ if (!found) {
+ mutex_unlock(&fmp->lock);
Here too: "goto out_err".
+ pr_err("kvmi: address %016lx not mapped\n", vaddr);
+ return -ENOENT;
+ }
+
+ /* decouple guest mapping */
+ list_del(&pmp->map_list);
+ mutex_unlock(&fmp->lock);
In kvm_dev_ioctl_map(), the fmp mutex is held across the _do_mapping()
call. Is there any particular reason why here the mutex doesn't need to
be held across the _do_unmapping() call? Or was that more an artifact of
having a common "out_err" exit in kvm_dev_ioctl_map()?
+
+ /* unmap & ignore result */
+ _do_unmapping(pmp->paddr);
+
+ /* free guest mapping */
+ kfree(pmp);
+
+ return 0;
+}
+
+static long kvm_dev_ioctl(struct file *filp,
+ unsigned int ioctl, unsigned long arg)
+{
+ void __user *argp = (void __user *) arg;
+ struct file_map *fmp;
+ long result;
+
+ /* minor check */
+ fmp = filp->private_data;
+ ASSERT(fmp->file == filp);
+
+ switch (ioctl) {
+ case KVM_INTRO_MEM_MAP: {
+ struct kvmi_mem_map map;
+
+ result = -EFAULT;
+ if (copy_from_user(&map, argp, sizeof(map)))
+ break;
+
+ result = kvm_dev_ioctl_map(fmp, &map);
+ if (IS_ERR_VALUE(result))
+ break;
+
+ result = 0;
+ break;
+ }
Since kvm_dev_ioctl_map() either returns an error or 0, couldn't this
just be reduced to:
result = kvm_dev_ioctl_map(fmap, &map);
break;
}
+ case KVM_INTRO_MEM_UNMAP: {
+ unsigned long vaddr = (unsigned long) arg;
+
+ result = kvm_dev_ioctl_unmap(fmp, vaddr);
+ if (IS_ERR_VALUE(result))
+ break;
+
+ result = 0;
+ break;
+ }
Ditto here.
+ default:
+ pr_err("kvmi: ioctl %d not implemented\n", ioctl);
+ result = -ENOTTY;
+ }
+
+ return result;
+}
+
+static int kvm_dev_release(struct inode *inodep, struct file *filp)
+{
+ int result = 0;
You set "result = 0" here, but result isn't used until the end, and just
to return it.
+ struct file_map *fmp;
+ struct list_head *cur, *next;
+ struct page_map *pmp;
+
+ pr_debug("kvmi: file %016lx closed by process %s\n",
+ (unsigned long) filp, current->comm);
+
+ /* acquire the file */
+ fmp = filp->private_data;
+ mutex_lock(&fmp->lock);
+
+ /* mark for teardown */
+ fmp->active = 0;
+
+ /* release mappings taken on this instance of the file */
+ list_for_each_safe(cur, next, &fmp->map_list) {
+ pmp = list_entry(cur, struct page_map, map_list);
+
+ /* unmap address */
+ _do_unmapping(pmp->paddr);
+
+ /* decouple & free guest mapping */
+ list_del(&pmp->map_list);
+ kfree(pmp);
+ }
+
+ /* done processing this file mapping */
+ mutex_unlock(&fmp->lock);
+
+ /* decouple file mapping */
+ spin_lock(&file_lock);
+ list_del(&fmp->file_list);
+ spin_unlock(&file_lock);
+
+ /* free it */
+ kfree(fmp);
+
+ return result;
This is the first time result is used. Couldn't this just be replaced
with "return 0"?
+}
+
+
+static const struct file_operations kvmmem_ops = {
+ .open = kvm_dev_open,
+ .unlocked_ioctl = kvm_dev_ioctl,
+ .compat_ioctl = kvm_dev_ioctl,
+ .release = kvm_dev_release,
+};
Here you have all the rvals aligned...
+
+static struct miscdevice kvm_mem_dev = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "kvmmem",
+ .fops = &kvmmem_ops,
+};
...but here you don't. I'm not sure what the "proper" style is, but I
think it should at least just be consistent.
+
+int __init kvm_intro_guest_init(void)
+{
+ int result;
+
+ if (!kvm_para_available()) {
+ pr_err("kvmi: paravirt not available\n");
+ return -EPERM;
+ }
+
+ result = misc_register(&kvm_mem_dev);
+ if (result) {
+ pr_err("kvmi: misc device register failed: %d\n", result);
+ return result;
+ }
+
+ INIT_LIST_HEAD(&file_list);
+ spin_lock_init(&file_lock);
+
+ pr_info("kvmi: guest introspection device created\n");
+
+ return 0;
+}
+
+void kvm_intro_guest_exit(void)
+{
+ misc_deregister(&kvm_mem_dev);
+}
+
+module_init(kvm_intro_guest_init)
+module_exit(kvm_intro_guest_exit)
Patrick
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