linux-kernel - [PATCH v2 3/9] KVM: arm64: Enable UBSAN_BOUNDS for the both the kernel and hyp/nVHE

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Message-Id: <20210114172338.2798389-4-lenaptr@google.com>
Date:   Thu, 14 Jan 2021 17:23:33 +0000
From:   Elena Petrova <lenaptr@...gle.com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     Elena Petrova <lenaptr@...gle.com>,
        linux-arm-kernel@...ts.infradead.org,
        open list <linux-kernel@...r.kernel.org>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        George Popescu <george.apopescu97@...il.com>,
        George Popescu <georgepope@...gle.com>
Subject: [PATCH v2 3/9] 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 from the buffer is straightforward.

Signed-off-by: George Popescu <georgepope@...gle.com>
Signed-off-by: Elena Petrova <lenaptr@...gle.com>
---
 arch/arm64/include/asm/kvm_ubsan.h | 19 ++++++++++++++++++-
 arch/arm64/kvm/hyp/nvhe/ubsan.c    | 14 ++++++++++++--
 arch/arm64/kvm/kvm_ubsan_buffer.c  | 10 ++++++++++
 3 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_ubsan.h b/arch/arm64/include/asm/kvm_ubsan.h
index fb32c7fd65d4..4f471acb88b0 100644
--- a/arch/arm64/include/asm/kvm_ubsan.h
+++ b/arch/arm64/include/asm/kvm_ubsan.h
@@ -9,6 +9,23 @@
 #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_OUT_OF_BOUNDS,
+	} type;
+	union {
+		struct out_of_bounds_data out_of_bounds_data;
+	};
+	union {
+		struct ubsan_values u_val;
+	};
 };
+
+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 8a194fb1f6cf..55a8f6db8555 100644
--- a/arch/arm64/kvm/hyp/nvhe/ubsan.c
+++ b/arch/arm64/kvm/hyp/nvhe/ubsan.c
@@ -13,7 +13,6 @@
 #include <asm/kvm_ubsan.h>
 #include <asm/kvm_debug_buffer.h>
 #include <kvm/arm_pmu.h>
-#include <ubsan.h>
 
 DEFINE_KVM_DEBUG_BUFFER(struct kvm_ubsan_info, kvm_ubsan_buffer,
                 kvm_ubsan_buff_wr_ind, KVM_UBSAN_BUFFER_SIZE);
@@ -44,7 +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;
+	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 4a1959ba9f68..a1523f86be3c 100644
--- a/arch/arm64/kvm/kvm_ubsan_buffer.c
+++ b/arch/arm64/kvm/kvm_ubsan_buffer.c
@@ -17,6 +17,15 @@
 DECLARE_KVM_DEBUG_BUFFER(struct kvm_ubsan_info, kvm_ubsan_buffer,
 		kvm_ubsan_buff_wr_ind, KVM_UBSAN_BUFFER_SIZE);
 
+void __kvm_check_ubsan_data(struct kvm_ubsan_info *slot)
+{
+	switch (slot->type) {
+	case UBSAN_OUT_OF_BOUNDS:
+		__ubsan_handle_out_of_bounds(&slot->out_of_bounds_data,
+				slot->u_val.lval);
+		break;
+	}
+}
 
 void iterate_kvm_ubsan_buffer(unsigned long left, unsigned long right)
 {
@@ -26,6 +35,7 @@ void iterate_kvm_ubsan_buffer(unsigned long left, unsigned long right)
 	slot = (struct kvm_ubsan_info *) this_cpu_ptr_nvhe_sym(kvm_ubsan_buffer);
 	for (i = left; i < right; ++i) {
 		/* check ubsan data */
+		__kvm_check_ubsan_data(slot + i);
 		slot[i].type = 0;
 	}
 }
-- 
2.30.0.284.gd98b1dd5eaa7-goog