IB/uverbs: Always use the attribute size provided by the user

This fixes several bugs around the copy_to/from user path:
 - copy_to used the user provided size of the attribute
   and could copy data beyond the end of the kernel buffer into
   userspace.
 - copy_from didn't know the size of the kernel buffer and
   could have left kernel memory unexpectedly un-initialized.
 - copy_from did not use the user length to determine if the
   attribute data is inlined or not.
Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/uverbs_std_types.c

@@ -323,7 +323,8 @@ static int uverbs_create_cq_handler(struct ib_device *ib_dev,
 	cq->res.type = RDMA_RESTRACK_CQ;
 	rdma_restrack_add(&cq->res);
 
-	ret = uverbs_copy_to(attrs, CREATE_CQ_RESP_CQE, &cq->cqe);
+	ret = uverbs_copy_to(attrs, CREATE_CQ_RESP_CQE, &cq->cqe,
+			     sizeof(cq->cqe));
 	if (ret)
 		goto err_cq;
 
@@ -375,7 +376,7 @@ static int uverbs_destroy_cq_handler(struct ib_device *ib_dev,
 	resp.comp_events_reported  = obj->comp_events_reported;
 	resp.async_events_reported = obj->async_events_reported;
 
-	return uverbs_copy_to(attrs, DESTROY_CQ_RESP, &resp);
+	return uverbs_copy_to(attrs, DESTROY_CQ_RESP, &resp, sizeof(resp));
 }
 
 static DECLARE_UVERBS_METHOD(

include/rdma/uverbs_ioctl.h

@@ -351,29 +351,50 @@ static inline const struct uverbs_attr *uverbs_attr_get(const struct uverbs_attr
 }
 
 static inline int uverbs_copy_to(const struct uverbs_attr_bundle *attrs_bundle,
-				 size_t idx, const void *from)
+				 size_t idx, const void *from, size_t size)
 {
 	const struct uverbs_attr *attr = uverbs_attr_get(attrs_bundle, idx);
 	u16 flags;
+	size_t min_size;
 
 	if (IS_ERR(attr))
 		return PTR_ERR(attr);
 
+	min_size = min_t(size_t, attr->ptr_attr.len, size);
+	if (copy_to_user(attr->ptr_attr.ptr, from, min_size))
+		return -EFAULT;
+
 	flags = attr->ptr_attr.flags | UVERBS_ATTR_F_VALID_OUTPUT;
-	return (!copy_to_user(attr->ptr_attr.ptr, from, attr->ptr_attr.len) &&
-		!put_user(flags, &attr->uattr->flags)) ? 0 : -EFAULT;
+	if (put_user(flags, &attr->uattr->flags))
+		return -EFAULT;
+
+	return 0;
 }
 
-static inline int _uverbs_copy_from(void *to, size_t to_size,
+static inline bool uverbs_attr_ptr_is_inline(const struct uverbs_attr *attr)
+{
+	return attr->ptr_attr.len <= sizeof(attr->ptr_attr.data);
+}
+
+static inline int _uverbs_copy_from(void *to,
 				    const struct uverbs_attr_bundle *attrs_bundle,
-				    size_t idx)
+				    size_t idx,
+				    size_t size)
 {
 	const struct uverbs_attr *attr = uverbs_attr_get(attrs_bundle, idx);
 
 	if (IS_ERR(attr))
 		return PTR_ERR(attr);
 
-	if (to_size <= sizeof(((struct ib_uverbs_attr *)0)->data))
+	/*
+	 * Validation ensures attr->ptr_attr.len >= size. If the caller is
+	 * using UVERBS_ATTR_SPEC_F_MIN_SZ then it must call copy_from with
+	 * the right size.
+	 */
+	if (unlikely(size < attr->ptr_attr.len))
+		return -EINVAL;
+
+	if (uverbs_attr_ptr_is_inline(attr))
 		memcpy(to, &attr->ptr_attr.data, attr->ptr_attr.len);
 	else if (copy_from_user(to, attr->ptr_attr.ptr, attr->ptr_attr.len))
 		return -EFAULT;
@@ -382,7 +403,7 @@ static inline int _uverbs_copy_from(void *to, size_t to_size,
 }
 
 #define uverbs_copy_from(to, attrs_bundle, idx)				      \
-	_uverbs_copy_from(to, sizeof(*(to)), attrs_bundle, idx)
+	_uverbs_copy_from(to, attrs_bundle, idx, sizeof(*to))
 
 /* =================================================
  *	 Definitions -> Specs infrastructure