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From:   George-Aurelian Popescu <georgepope@google.com>
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        masahiroy@kernel.org, michal.lkml@markovi.net
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        George Popescu <georgepope@google.com>
Subject: [PATCH 11/14] KVM: arm64: Detect type mismatch undefined behaviour from hyp/nVHE code
Date:   Mon, 14 Sep 2020 17:27:47 +0000
Message-Id: <20200914172750.852684-12-georgepope@google.com>
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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