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

[George-Aurelian Popescu]

From: George Popescu <georgep...@google.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 <georgep...@google.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