[PATCH 11/14] KVM: arm64: Detect type mismatch undefined behaviour from hyp/nVHE code

George-Aurelian Popescu
2020-09-14T17:32:17Z

From: George Popescu <georgepope@google.com>

Type mismatch undefined behaviour handler provides two handlers with two
data structures type_mismatch_data and type_mismatch_data_v1. Both can be
stored inside a common data structure: type_mismatch_data_common, which
differs of type_mismatch_data only by keeping a pointer to a
struct source_location instead of the value of the struct.

In this way, the buffer keeps the data encapsulated inside of a struct
type_mismatch_data, because pointers from nVHE can not be passed to the
kernel.

Inside the kernel call the __ubsan_handle_type_mismatch_data with the
data from the buffer.

Signed-off-by: George Popescu <georgepope@google.com>
---
arch/arm64/include/asm/kvm_ubsan.h | 6 ++++-
arch/arm64/kvm/hyp/nvhe/ubsan.c | 41 ++++++++++++++++++++++++++++--
arch/arm64/kvm/kvm_ubsan_buffer.c | 5 +++-
3 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_ubsan.h b/arch/arm64/include/asm/kvm_ubsan.h
index b643ac9a4090..a9f499f4ef6d 100644
--- a/arch/arm64/include/asm/kvm_ubsan.h
+++ b/arch/arm64/include/asm/kvm_ubsan.h
@@ -23,13 +23,15 @@ struct kvm_ubsan_info {
UBSAN_OUT_OF_BOUNDS,
UBSAN_UNREACHABLE_DATA,
UBSAN_SHIFT_OUT_OF_BOUNDS,
- UBSAN_INVALID_DATA
+ UBSAN_INVALID_DATA,
+ UBSAN_TYPE_MISMATCH
} type;
union {
struct out_of_bounds_data out_of_bounds_data;
struct unreachable_data unreachable_data;
struct shift_out_of_bounds_data shift_out_of_bounds_data;
struct invalid_value_data invalid_value_data;
+ struct type_mismatch_data type_mismatch_data;
};
union {
struct ubsan_values u_val;
@@ -41,3 +43,5 @@ void __ubsan_handle_out_of_bounds(void *_data, void *index);
void __ubsan_handle_builtin_unreachable(void *_data);
void __ubsan_handle_shift_out_of_bounds(void *_data, void *lhs, void *rhs);
void __ubsan_handle_load_invalid_value(void *_data, void *val);
+void __ubsan_handle_type_mismatch(struct type_mismatch_data *_data, void *ptr);
+
diff --git a/arch/arm64/kvm/hyp/nvhe/ubsan.c b/arch/arm64/kvm/hyp/nvhe/ubsan.c
index 1888a1f51724..c99d919105aa 100644
--- a/arch/arm64/kvm/hyp/nvhe/ubsan.c
+++ b/arch/arm64/kvm/hyp/nvhe/ubsan.c
@@ -29,6 +29,24 @@ static inline struct kvm_ubsan_info *kvm_ubsan_buffer_next_slot(void)
return res;
}

+static void write_type_mismatch_data(struct type_mismatch_data_common *data, void *lval)
+{
+ struct kvm_ubsan_info *slot;
+ struct type_mismatch_data *aux_cont;
+
+ slot = kvm_ubsan_buffer_next_slot();
+ if (slot) {
+ slot->type = UBSAN_TYPE_MISMATCH;
+ aux_cont = &slot->type_mismatch_data;
+ aux_cont->location.file_name = data->location->file_name;
+ aux_cont->location.reported = data->location->reported;
+ aux_cont->type = data->type;
+ aux_cont->alignment = data->alignment;
+ aux_cont->type_check_kind = data->type_check_kind;
+ slot->u_val.lval = lval;
+ }
+}
+
void __ubsan_handle_add_overflow(void *_data, void *lhs, void *rhs) {}

void __ubsan_handle_sub_overflow(void *_data, void *lhs, void *rhs) {}
@@ -39,9 +57,28 @@ void __ubsan_handle_negate_overflow(void *_data, void *old_val) {}

void __ubsan_handle_divrem_overflow(void *_data, void *lhs, void *rhs) {}

-void __ubsan_handle_type_mismatch(struct type_mismatch_data *data, void *ptr) {}
+void __ubsan_handle_type_mismatch(struct type_mismatch_data *data, void *ptr)
+{
+ struct type_mismatch_data_common common_data = {
+ .location = &data->location,
+ .type = data->type,
+ .alignment = data->alignment,
+ .type_check_kind = data->type_check_kind
+ };
+ write_type_mismatch_data(&common_data, ptr);
+}

-void __ubsan_handle_type_mismatch_v1(void *_data, void *ptr) {}
+void __ubsan_handle_type_mismatch_v1(void *_data, void *ptr)
+{
+ struct type_mismatch_data_v1 *data = _data;
+ struct type_mismatch_data_common common_data = {
+ .location = &data->location,
+ .type = data->type,
+ .alignment = 1UL << data->log_alignment,
+ .type_check_kind = data->type_check_kind
+ };
+ write_type_mismatch_data(&common_data, ptr);
+}

void __ubsan_handle_out_of_bounds(void *_data, void *index)
{
diff --git a/arch/arm64/kvm/kvm_ubsan_buffer.c b/arch/arm64/kvm/kvm_ubsan_buffer.c
index 01bf2171af9e..21c242c92f0a 100644
--- a/arch/arm64/kvm/kvm_ubsan_buffer.c
+++ b/arch/arm64/kvm/kvm_ubsan_buffer.c
@@ -36,6 +36,10 @@ void __kvm_check_ubsan_data(struct kvm_ubsan_info *slot)
__ubsan_handle_load_invalid_value(&slot->invalid_value_data,
slot->u_val.lval);
break;
+ case UBSAN_TYPE_MISMATCH:
+ __ubsan_handle_type_mismatch(&slot->type_mismatch_data,
+ slot->u_val.lval);
+ break;
}
}

@@ -51,4 +55,3 @@ void __kvm_check_ubsan_buffer(void)
slot->type = 0;
}
}
-
--
2.28.0.618.gf4bc123cb7-goog