Re: [patch 3/4] KVM: introduce kvm_arch_can_free_memslot, disallow slot deletion if cached cr3
mtosa...@redhat.com wrote:
Disallow the deletion of memory slots (and aliases, for x86 case), if a
vcpu contains a cr3 that points to such slot/alias.
This complements commit 6c20e1442bb1c62914bb85b7f4a38973d2a423ba.
v2:
- set KVM_REQ_TRIPLE_FAULT
- use __KVM_HAVE_ARCH_CAN_FREE_MEMSLOT to avoid duplication of stub
Signed-off-by: Marcelo Tosatti mtosa...@redhat.com
Index: kvm-pending/arch/x86/kvm/x86.c
===
--- kvm-pending.orig/arch/x86/kvm/x86.c
+++ kvm-pending/arch/x86/kvm/x86.c
@@ -1636,6 +1636,29 @@ gfn_t unalias_gfn(struct kvm *kvm, gfn_t
return gfn;
}
+static int kvm_root_gfn_in_range(struct kvm *kvm, gfn_t base_gfn,
+gfn_t end_gfn, bool unalias)
+{
+ struct kvm_vcpu *vcpu;
+ gfn_t root_gfn;
+ int i;
+
+ for (i = 0; i KVM_MAX_VCPUS; ++i) {
+ vcpu = kvm-vcpus[i];
+ if (!vcpu)
+ continue;
+ root_gfn = vcpu-arch.cr3 PAGE_SHIFT;
The guest may have changed this by now.
+ if (unalias)
+ root_gfn = unalias_gfn(kvm, root_gfn);
+ if (root_gfn = base_gfn root_gfn = end_gfn) {
+ set_bit(KVM_REQ_TRIPLE_FAULT, vcpu-requests);
+ return 1;
+ }
+ }
+
+ return 0;
+}
+
The naming is bad, a function named as a predicate shouldn't have side
effects.
Also, we should allow deleting the slot. There's no reason to deny
userspace something just because the guest is playing around
I think this should be enough:
- take mmu lock
- request an mmu reload from all vcpus
- drop the slot
- release mmu lock
The reload will inject a #GP if cr3 is now out of bounds, should be
changed to triple fault, but everything is in place (set_cr3 already
checks).
--
error compiling committee.c: too many arguments to function
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Re: [patch 3/4] KVM: introduce kvm_arch_can_free_memslot, disallow slot deletion if cached cr3
mtosa...@redhat.com wrote:
Disallow the deletion of memory slots (and aliases, for x86 case), if a
vcpu contains a cr3 that points to such slot/alias.
That allows the guest to induce failures in the host. Better to
triple-fault the guest instead.
+int kvm_arch_can_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ return 1;
+}
+
In general, instead of stubs in every arch, have x86 say
KVM_HAVE_ARCH_CAN_FREE_MEMSLOT and define the stub in generic code when
that define is not present.
--
error compiling committee.c: too many arguments to function
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Re: [patch 3/4] KVM: introduce kvm_arch_can_free_memslot, disallow slot deletion if cached cr3
On Thu, May 07, 2009 at 05:16:35PM +0300, Avi Kivity wrote:
mtosa...@redhat.com wrote:
Disallow the deletion of memory slots (and aliases, for x86 case), if a
vcpu contains a cr3 that points to such slot/alias.
That allows the guest to induce failures in the host.
I don't understand what you mean. What is the problem with returning
errors in the ioctl handlers?
The guest can cause an overflow in qemu, overwrite the parameters to
KVM_GET_MSR_INDEX_LIST in an attempt to read kernel data, and get
-E2BIG. Or pick your combination.
Better to triple-fault the guest instead.
Sure can additionally triple fault it, but the kernel might attempt to
access the non-existant slot which cr3 points to before TRIPLE_FAULT is
processed. So you have to avoid that possibility in the first place,
thats why the patch modifies the ioctls to fail.
+int kvm_arch_can_free_memslot(struct kvm *kvm, struct kvm_memory_slot
*slot)
+{
+return 1;
+}
+
In general, instead of stubs in every arch, have x86 say
KVM_HAVE_ARCH_CAN_FREE_MEMSLOT and define the stub in generic code when
that define is not present.
Will fix that.
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[patch 3/4] KVM: introduce kvm_arch_can_free_memslot, disallow slot deletion if cached cr3
Disallow the deletion of memory slots (and aliases, for x86 case), if a
vcpu contains a cr3 that points to such slot/alias.
This complements commit 6c20e1442bb1c62914bb85b7f4a38973d2a423ba.
v2:
- set KVM_REQ_TRIPLE_FAULT
- use __KVM_HAVE_ARCH_CAN_FREE_MEMSLOT to avoid duplication of stub
Signed-off-by: Marcelo Tosatti mtosa...@redhat.com
Index: kvm-pending/arch/x86/kvm/x86.c
===
--- kvm-pending.orig/arch/x86/kvm/x86.c
+++ kvm-pending/arch/x86/kvm/x86.c
@@ -1636,6 +1636,29 @@ gfn_t unalias_gfn(struct kvm *kvm, gfn_t
return gfn;
}
+static int kvm_root_gfn_in_range(struct kvm *kvm, gfn_t base_gfn,
+gfn_t end_gfn, bool unalias)
+{
+ struct kvm_vcpu *vcpu;
+ gfn_t root_gfn;
+ int i;
+
+ for (i = 0; i KVM_MAX_VCPUS; ++i) {
+ vcpu = kvm-vcpus[i];
+ if (!vcpu)
+ continue;
+ root_gfn = vcpu-arch.cr3 PAGE_SHIFT;
+ if (unalias)
+ root_gfn = unalias_gfn(kvm, root_gfn);
+ if (root_gfn = base_gfn root_gfn = end_gfn) {
+ set_bit(KVM_REQ_TRIPLE_FAULT, vcpu-requests);
+ return 1;
+ }
+ }
+
+ return 0;
+}
+
/*
* Set a new alias region. Aliases map a portion of physical memory into
* another portion. This is useful for memory windows, for example the PC
@@ -1666,6 +1689,19 @@ static int kvm_vm_ioctl_set_memory_alias
spin_lock(kvm-mmu_lock);
p = kvm-arch.aliases[alias-slot];
+
+ /* FIXME: either disallow shrinking alias slots or disable
+* size changes as done with memslots
+*/
+ if (!alias-memory_size) {
+ r = -EBUSY;
+ if (kvm_root_gfn_in_range(kvm, p-base_gfn,
+ p-base_gfn + p-npages - 1,
+ false))
+ goto out_unlock;
+ }
+
+
p-base_gfn = alias-guest_phys_addr PAGE_SHIFT;
p-npages = alias-memory_size PAGE_SHIFT;
p-target_gfn = alias-target_phys_addr PAGE_SHIFT;
@@ -1682,6 +1718,9 @@ static int kvm_vm_ioctl_set_memory_alias
return 0;
+out_unlock:
+ spin_unlock(kvm-mmu_lock);
+ up_write(kvm-slots_lock);
out:
return r;
}
@@ -4552,6 +4591,15 @@ void kvm_arch_flush_shadow(struct kvm *k
kvm_mmu_zap_all(kvm);
}
+int kvm_arch_can_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ int ret;
+
+ ret = kvm_root_gfn_in_range(kvm, slot-base_gfn,
+ slot-base_gfn + slot-npages - 1, true);
+ return !ret;
+}
+
int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
{
return vcpu-arch.mp_state == KVM_MP_STATE_RUNNABLE
Index: kvm-pending/include/linux/kvm_host.h
===
--- kvm-pending.orig/include/linux/kvm_host.h
+++ kvm-pending/include/linux/kvm_host.h
@@ -200,6 +200,7 @@ int kvm_arch_set_memory_region(struct kv
struct kvm_memory_slot old,
int user_alloc);
void kvm_arch_flush_shadow(struct kvm *kvm);
+int kvm_arch_can_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot);
gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn);
struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn);
unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn);
Index: kvm-pending/virt/kvm/kvm_main.c
===
--- kvm-pending.orig/virt/kvm/kvm_main.c
+++ kvm-pending/virt/kvm/kvm_main.c
@@ -1061,6 +1061,13 @@ static int kvm_vm_release(struct inode *
return 0;
}
+#ifndef __KVM_HAVE_ARCH_CAN_FREE_MEMSLOT
+int kvm_arch_can_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ return 1;
+}
+#endif
+
/*
* Allocate some memory and give it an address in the guest physical address
* space.
@@ -1179,8 +1186,13 @@ int __kvm_set_memory_region(struct kvm *
}
#endif /* not defined CONFIG_S390 */
- if (!npages)
+ if (!npages) {
kvm_arch_flush_shadow(kvm);
+ if (!kvm_arch_can_free_memslot(kvm, memslot)) {
+ r = -EBUSY;
+ goto out_free;
+ }
+ }
spin_lock(kvm-mmu_lock);
if (mem-slot = kvm-nmemslots)
Index: kvm-pending/arch/x86/include/asm/kvm.h
===
--- kvm-pending.orig/arch/x86/include/asm/kvm.h
+++ kvm-pending/arch/x86/include/asm/kvm.h
@@ -18,6 +18,8 @@
#define __KVM_HAVE_GUEST_DEBUG
#define __KVM_HAVE_MSIX
+#define __KVM_HAVE_ARCH_CAN_FREE_MEMSLOT
+
/* Architectural interrupt line count. */
#define KVM_NR_INTERRUPTS 256
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[patch 3/4] KVM: introduce kvm_arch_can_free_memslot, disallow slot deletion if cached cr3
Disallow the deletion of memory slots (and aliases, for x86 case), if a
vcpu contains a cr3 that points to such slot/alias.
This complements commit 6c20e1442bb1c62914bb85b7f4a38973d2a423ba.
Signed-off-by: Marcelo Tosatti mtosa...@redhat.com
Index: kvm/arch/ia64/kvm/kvm-ia64.c
===
--- kvm.orig/arch/ia64/kvm/kvm-ia64.c
+++ kvm/arch/ia64/kvm/kvm-ia64.c
@@ -1633,6 +1633,11 @@ void kvm_arch_flush_shadow(struct kvm *k
kvm_flush_remote_tlbs(kvm);
}
+int kvm_arch_can_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ return 1;
+}
+
long kvm_arch_dev_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg)
{
Index: kvm/arch/powerpc/kvm/powerpc.c
===
--- kvm.orig/arch/powerpc/kvm/powerpc.c
+++ kvm/arch/powerpc/kvm/powerpc.c
@@ -176,6 +176,11 @@ void kvm_arch_flush_shadow(struct kvm *k
{
}
+int kvm_arch_can_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ return 1;
+}
+
struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id)
{
struct kvm_vcpu *vcpu;
Index: kvm/arch/s390/kvm/kvm-s390.c
===
--- kvm.orig/arch/s390/kvm/kvm-s390.c
+++ kvm/arch/s390/kvm/kvm-s390.c
@@ -691,6 +691,11 @@ void kvm_arch_flush_shadow(struct kvm *k
{
}
+int kvm_arch_can_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ return 1;
+}
+
gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
{
return gfn;
Index: kvm/arch/x86/kvm/x86.c
===
--- kvm.orig/arch/x86/kvm/x86.c
+++ kvm/arch/x86/kvm/x86.c
@@ -1676,6 +1676,27 @@ gfn_t unalias_gfn(struct kvm *kvm, gfn_t
return gfn;
}
+static int kvm_root_gfn_in_range(struct kvm *kvm, gfn_t base_gfn,
+gfn_t end_gfn, bool unalias)
+{
+ struct kvm_vcpu *vcpu;
+ gfn_t root_gfn;
+ int i;
+
+ for (i = 0; i KVM_MAX_VCPUS; ++i) {
+ vcpu = kvm-vcpus[i];
+ if (!vcpu)
+ continue;
+ root_gfn = vcpu-arch.cr3 PAGE_SHIFT;
+ if (unalias)
+ root_gfn = unalias_gfn(kvm, root_gfn);
+ if (root_gfn = base_gfn root_gfn = end_gfn)
+ return 1;
+ }
+
+ return 0;
+}
+
/*
* Set a new alias region. Aliases map a portion of physical memory into
* another portion. This is useful for memory windows, for example the PC
@@ -1706,6 +1727,19 @@ static int kvm_vm_ioctl_set_memory_alias
spin_lock(kvm-mmu_lock);
p = kvm-arch.aliases[alias-slot];
+
+ /* FIXME: either disallow shrinking alias slots or disable
+* size changes as done with memslots
+*/
+ if (!alias-memory_size) {
+ r = -EBUSY;
+ if (kvm_root_gfn_in_range(kvm, p-base_gfn,
+ p-base_gfn + p-npages - 1,
+ false))
+ goto out_unlock;
+ }
+
+
p-base_gfn = alias-guest_phys_addr PAGE_SHIFT;
p-npages = alias-memory_size PAGE_SHIFT;
p-target_gfn = alias-target_phys_addr PAGE_SHIFT;
@@ -1722,6 +1756,9 @@ static int kvm_vm_ioctl_set_memory_alias
return 0;
+out_unlock:
+ spin_unlock(kvm-mmu_lock);
+ up_write(kvm-slots_lock);
out:
return r;
}
@@ -4532,6 +4569,15 @@ void kvm_arch_flush_shadow(struct kvm *k
kvm_mmu_zap_all(kvm);
}
+int kvm_arch_can_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ int ret;
+
+ ret = kvm_root_gfn_in_range(kvm, slot-base_gfn,
+ slot-base_gfn + slot-npages - 1, true);
+ return !ret;
+}
+
int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
{
return vcpu-arch.mp_state == KVM_MP_STATE_RUNNABLE
Index: kvm/include/linux/kvm_host.h
===
--- kvm.orig/include/linux/kvm_host.h
+++ kvm/include/linux/kvm_host.h
@@ -200,6 +200,7 @@ int kvm_arch_set_memory_region(struct kv
struct kvm_memory_slot old,
int user_alloc);
void kvm_arch_flush_shadow(struct kvm *kvm);
+int kvm_arch_can_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot);
gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn);
struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn);
unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn);
Index: kvm/virt/kvm/kvm_main.c
===
--- kvm.orig/virt/kvm/kvm_main.c
+++ kvm/virt/kvm/kvm_main.c
@@ -1179,8 +1179,13 @@ int __kvm_set_memory_region(struct kvm *
}
#endif /* not defined CONFIG_S390 */
- if (!npages)
+ if (!npages) {
