linux-kernel - [PATCH v3 5/9] KVM: arm64: Enable shift out of bounds undefined behaviour check for hyp/nVHE

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Date:   Fri, 15 Jan 2021 17:18:26 +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 v3 5/9] KVM: arm64: Enable shift out of bounds undefined
 behaviour check for hyp/nVHE

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

__ubsan_handle_shift_out_of_bounds data is passed to the buffer inside
hyp/nVHE. This data is passed to the original handler from kernel.

The 64bit values of the shift expression operands are stored as the lhs
and rhs pointers, so there is no need to dereference them.

Signed-off-by: George Popescu <georgepope@...gle.com>
Signed-off-by: Elena Petrova <lenaptr@...gle.com>
---
 arch/arm64/include/asm/kvm_ubsan.h |  5 ++++-
 arch/arm64/kvm/hyp/nvhe/ubsan.c    | 14 +++++++++++++-
 arch/arm64/kvm/kvm_ubsan_buffer.c  |  4 ++++
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_ubsan.h b/arch/arm64/include/asm/kvm_ubsan.h
index 70c6f2541d07..0eef0e11a93b 100644
--- a/arch/arm64/include/asm/kvm_ubsan.h
+++ b/arch/arm64/include/asm/kvm_ubsan.h
@@ -19,11 +19,13 @@ struct ubsan_values {
 struct kvm_ubsan_info {
 	enum {
 		UBSAN_OUT_OF_BOUNDS,
-		UBSAN_UNREACHABLE_DATA
+		UBSAN_UNREACHABLE_DATA,
+		UBSAN_SHIFT_OUT_OF_BOUNDS
 	} 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;
 	};
 	union {
 		struct ubsan_values u_val;
@@ -32,3 +34,4 @@ struct kvm_ubsan_info {
 
 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);
diff --git a/arch/arm64/kvm/hyp/nvhe/ubsan.c b/arch/arm64/kvm/hyp/nvhe/ubsan.c
index 5e55897b2d72..1069ed5036d5 100644
--- a/arch/arm64/kvm/hyp/nvhe/ubsan.c
+++ b/arch/arm64/kvm/hyp/nvhe/ubsan.c
@@ -56,7 +56,19 @@ void __ubsan_handle_out_of_bounds(void *_data, void *index)
 	}
 }
 
-void __ubsan_handle_shift_out_of_bounds(void *_data, void *lhs, void *rhs) {}
+void __ubsan_handle_shift_out_of_bounds(void *_data, void *lhs, void *rhs)
+{
+	struct kvm_ubsan_info *slot;
+	struct shift_out_of_bounds_data *data = _data;
+
+	slot = kvm_ubsan_buffer_next_slot();
+	if (slot) {
+		slot->type = UBSAN_SHIFT_OUT_OF_BOUNDS;
+		slot->shift_out_of_bounds_data = *data;
+		slot->u_val.lval = lhs;
+		slot->u_val.rval = rhs;
+	}
+}
 
 void __ubsan_handle_builtin_unreachable(void *_data)
 {
diff --git a/arch/arm64/kvm/kvm_ubsan_buffer.c b/arch/arm64/kvm/kvm_ubsan_buffer.c
index e51949c275aa..b80045883047 100644
--- a/arch/arm64/kvm/kvm_ubsan_buffer.c
+++ b/arch/arm64/kvm/kvm_ubsan_buffer.c
@@ -27,6 +27,10 @@ void __kvm_check_ubsan_data(struct kvm_ubsan_info *slot)
 	case UBSAN_UNREACHABLE_DATA:
 		__ubsan_handle_builtin_unreachable(&slot->unreachable_data);
 		break;
+	case UBSAN_SHIFT_OUT_OF_BOUNDS:
+        	__ubsan_handle_shift_out_of_bounds(&slot->shift_out_of_bounds_data,
+				slot->u_val.lval, slot->u_val.rval);
+		break;
 	}
 }
 
-- 
2.30.0.296.g2bfb1c46d8-goog