KVM: use struct_size() and flex_array_size() helpers in kvm_io_bus_unregister_dev()

Make use of the struct_size() helper to avoid any potential type
mistakes and protect against potential integer overflows
Make use of the flex_array_size() helper to calculate the size of a
flexible array member within an enclosing structure

Suggested-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Rustam Kovhaev <rkovhaev@gmail.com>
Message-Id: <20200918120500.954436-1-rkovhaev@gmail.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index cf88233b819a0803e7f47dd85552a9275b135a68..68edd25dcb11f8f72c984e7e182037a2cac342d7 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4350,10 +4350,10 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
        new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
                          GFP_KERNEL_ACCOUNT);
        if (new_bus) {
-               memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
+               memcpy(new_bus, bus, struct_size(bus, range, i));
                new_bus->dev_count--;
                memcpy(new_bus->range + i, bus->range + i + 1,
-                      (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
+                               flex_array_size(new_bus, range, new_bus->dev_count - i));
        } else {
                pr_err("kvm: failed to shrink bus, removing it completely\n");
                for (j = 0; j < bus->dev_count; j++) {