[PATCH v2 15/28] KVM: Take memory protections into account for memory read/write/fetch

[Paolo Bonzini]

From: Nicolas Saenz Julienne <nsaenz@xxxxxxxxxx>

Take into account memory attributes when accessing guest memory through
the kvm_{read,write,fetch}*() family of functions.

All of these pass a struct kvm_memory_slot pointer to the actual
workhorse functions, in order to share code between the VM-wide and
vCPU-specific version of the functions (the latter of which handles the
multi-address-space case).  For this reason they need specific changes
and do not work even though the gfn_to_hva() path has been taught already
about memory protection attributes.

Signed-off-by: Nicolas Saenz Julienne <nsaenz@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 virt/kvm/kvm_main.c | 34 ++++++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 7cb7ff202fc0..3932e526870a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3255,11 +3255,13 @@ static int next_segment(unsigned long len, int offset)
 }
 
 /* Copy @len bytes from guest memory at '(@gfn * PAGE_SIZE) + @offset' to @data */
-static int __kvm_read_guest_page(struct kvm_memory_slot *slot, gfn_t gfn,
-				 void *data, int offset, int len)
+static int __kvm_read_guest_page(struct kvm *kvm, struct kvm_memory_slot *slot,
+				 gfn_t gfn, void *data, int offset, int len,
+				 unsigned long attr)
 {
 	int r;
 	unsigned long addr;
+	unsigned long attrs;
 
 	if (WARN_ON_ONCE(offset + len > PAGE_SIZE))
 		return -EFAULT;
@@ -3267,6 +3269,11 @@ static int __kvm_read_guest_page(struct kvm_memory_slot *slot, gfn_t gfn,
 	addr = gfn_to_hva_memslot_prot(slot, gfn, NULL);
 	if (kvm_is_error_hva(addr))
 		return -EFAULT;
+
+	attrs = kvm_get_memory_attributes(kvm, gfn);
+	if (attrs & attr)
+		return -EFAULT;
+
 	r = __copy_from_user(data, (void __user *)addr + offset, len);
 	if (r)
 		return -EFAULT;
@@ -3278,7 +3285,8 @@ int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
 {
 	struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
 
-	return __kvm_read_guest_page(slot, gfn, data, offset, len);
+	return __kvm_read_guest_page(kvm, slot, gfn, data, offset, len,
+				     KVM_MEMORY_ATTRIBUTE_NR);
 }
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_read_guest_page);
 
@@ -3287,7 +3295,8 @@ int kvm_vcpu_read_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn, void *data,
 {
 	struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
 
-	return __kvm_read_guest_page(slot, gfn, data, offset, len);
+	return __kvm_read_guest_page(vcpu->kvm, slot, gfn, data, offset, len,
+				     KVM_MEMORY_ATTRIBUTE_NR);
 }
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_vcpu_read_guest_page);
 
@@ -3296,7 +3305,8 @@ int kvm_vcpu_fetch_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn, void *data,
 {
 	struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
 
-	return __kvm_read_guest_page(vcpu->kvm, slot, gfn, data, offset, len);
+	return __kvm_read_guest_page(vcpu->kvm, slot, gfn, data, offset, len,
+				     KVM_MEMORY_ATTRIBUTE_NX);
 }
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_vcpu_fetch_guest_page);
 
@@ -3340,8 +3350,9 @@ int kvm_vcpu_read_guest(struct kvm_vcpu *vcpu, gpa_t gpa, void *data, unsigned l
 }
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_vcpu_read_guest);
 
-static int __kvm_read_guest_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
-			           void *data, int offset, unsigned long len)
+static int __kvm_read_guest_atomic(struct kvm *kvm,
+				   struct kvm_memory_slot *slot, gfn_t gfn,
+				   void *data, int offset, unsigned long len)
 {
 	int r;
 	unsigned long addr;
@@ -3349,6 +3360,9 @@ static int __kvm_read_guest_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
 	if (WARN_ON_ONCE(offset + len > PAGE_SIZE))
 		return -EFAULT;
 
+	if (!kvm_mem_attributes_may_read_gfn(kvm, gfn))
+		return -EFAULT;
+
 	addr = gfn_to_hva_memslot_prot(slot, gfn, NULL);
 	if (kvm_is_error_hva(addr))
 		return -EFAULT;
@@ -3367,7 +3381,7 @@ int kvm_vcpu_read_guest_atomic(struct kvm_vcpu *vcpu, gpa_t gpa,
 	struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
 	int offset = offset_in_page(gpa);
 
-	return __kvm_read_guest_atomic(slot, gfn, data, offset, len);
+	return __kvm_read_guest_atomic(vcpu->kvm, slot, gfn, data, offset, len);
 }
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_vcpu_read_guest_atomic);
 
@@ -3385,6 +3399,10 @@ static int __kvm_write_guest_page(struct kvm *kvm,
 	addr = gfn_to_hva_memslot(memslot, gfn);
 	if (kvm_is_error_hva(addr))
 		return -EFAULT;
+
+	if (!kvm_mem_attributes_may_write_gfn(kvm, gfn))
+		return -EFAULT;
+
 	r = __copy_to_user((void __user *)addr + offset, data, len);
 	if (r)
 		return -EFAULT;
-- 
2.52.0