linux-kernel - [PATCH 07/14] KVM: arm64: Enable UBSAN_BOUNDS for the both the kernel and hyp/nVHE

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Date:   Mon, 14 Sep 2020 17:27:43 +0000
From:   George-Aurelian Popescu <georgepope@...gle.com>
To:     maz@...nel.org, catalin.marinas@....com, will@...nel.org,
        masahiroy@...nel.org, michal.lkml@...kovi.net
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        clang-built-linux@...glegroups.com, james.morse@....com,
        julien.thierry.kdev@...il.com, suzuki.poulose@....com,
        natechancellor@...il.com, ndesaulniers@...gle.com,
        dbrazdil@...gle.com, broonie@...nel.org, maskray@...gle.com,
        ascull@...gle.com, keescook@...omium.org,
        akpm@...ux-foundation.org, dvyukov@...gle.com, elver@...gle.com,
        tglx@...utronix.de, arnd@...db.de,
        George Popescu <georgepope@...gle.com>
Subject: [PATCH 07/14] KVM: arm64: Enable UBSAN_BOUNDS for the both the kernel and hyp/nVHE

From: George Popescu <georgepope@...gle.com>

If an out of bounds happens inside the hyp/nVHE code, the
ubsan_out_of_bounds handler stores the logging data inside the
kvm_ubsan_buffer. The one responsible for printing is the kernel
ubsan_out_of_bounds handler. The process of decapsulating the data happens
in kvm_ubsan_buffer.c.

The struct kvm_ubsan_info contains three main components:
-enum type, which is used to identify which handler to call from the
kernel.
-struct ubsan_values, which stores the operands involved during the
undefined behaviours, which can be one, two or zero, depending on what
undefiend behaviour is reported. As an example for: out_of_bounds there
is only one operand (the index).

Accessing a slot with no type should do nothing. Each slot is marked
with the UBSAN_NONE tag after it's first usage.

Signed-off-by: George Popescu <georgepope@...gle.com>
---
 arch/arm64/include/asm/kvm_ubsan.h | 19 ++++++++++++++++++-
 arch/arm64/kvm/hyp/nvhe/ubsan.c    | 13 ++++++++++++-
 arch/arm64/kvm/kvm_ubsan_buffer.c  | 13 ++++++++++++-
 3 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_ubsan.h b/arch/arm64/include/asm/kvm_ubsan.h
index af607a796376..575881e0bd5f 100644
--- a/arch/arm64/include/asm/kvm_ubsan.h
+++ b/arch/arm64/include/asm/kvm_ubsan.h
@@ -11,7 +11,24 @@
 #define UBSAN_MAX_TYPE 6
 #define KVM_UBSAN_BUFFER_SIZE 1000
 
+struct ubsan_values {
+	void *lval;
+	void *rval;
+	char op;
+};
+
 struct kvm_ubsan_info {
-	int type;
+	enum {
+		UBSAN_NONE,
+		UBSAN_OUT_OF_BOUNDS
+	} type;
+	union {
+		struct out_of_bounds_data out_of_bounds_data;
+	};
+	union {
+		struct ubsan_values u_val;
+	};
 };
 #endif
+
+void __ubsan_handle_out_of_bounds(void *_data, void *index);
diff --git a/arch/arm64/kvm/hyp/nvhe/ubsan.c b/arch/arm64/kvm/hyp/nvhe/ubsan.c
index a43c9646e1e8..b2d3404f6215 100644
--- a/arch/arm64/kvm/hyp/nvhe/ubsan.c
+++ b/arch/arm64/kvm/hyp/nvhe/ubsan.c
@@ -43,7 +43,18 @@ void __ubsan_handle_type_mismatch(struct type_mismatch_data *data, void *ptr) {}
 
 void __ubsan_handle_type_mismatch_v1(void *_data, void *ptr) {}
 
-void __ubsan_handle_out_of_bounds(void *_data, void *index) {}
+void __ubsan_handle_out_of_bounds(void *_data, void *index)
+{
+	struct kvm_ubsan_info *slot = NULL;
+	struct out_of_bounds_data *data = _data;
+
+	slot = kvm_ubsan_buffer_next_slot();
+	if (slot) {
+		slot->type = UBSAN_OUT_OF_BOUNDS;
+		slot->out_of_bounds_data = *data;
+		slot->u_val.lval = index;
+	}
+}
 
 void __ubsan_handle_shift_out_of_bounds(void *_data, void *lhs, void *rhs) {}
 
diff --git a/arch/arm64/kvm/kvm_ubsan_buffer.c b/arch/arm64/kvm/kvm_ubsan_buffer.c
index 28dcf19b5706..ce796bdd027e 100644
--- a/arch/arm64/kvm/kvm_ubsan_buffer.c
+++ b/arch/arm64/kvm/kvm_ubsan_buffer.c
@@ -16,6 +16,17 @@
 
 DECLARE_KVM_DEBUG_BUFFER(struct kvm_ubsan_info, kvm_ubsan_buff, KVM_UBSAN_BUFFER_SIZE);
 
+void __kvm_check_ubsan_data(struct kvm_ubsan_info *slot)
+{
+	switch (slot->type) {
+	case UBSAN_NONE:
+		break;
+	case UBSAN_OUT_OF_BOUNDS:
+		__ubsan_handle_out_of_bounds(&slot->out_of_bounds_data,
+				slot->u_val.lval);
+		break;
+	}
+}
 
 void __kvm_check_ubsan_buffer(void)
 {
@@ -25,7 +36,7 @@ void __kvm_check_ubsan_buffer(void)
 
 	init_kvm_debug_buffer(kvm_ubsan_buff, struct kvm_ubsan_info, slot, write_ind);
 	for_each_kvm_debug_buffer_slot(slot, write_ind, it) {
-		/* check ubsan data */
+		__kvm_check_ubsan_data(slot);
 		slot->type = 0;
 	}
 }
-- 
2.28.0.618.gf4bc123cb7-goog