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-rw-r--r--include/asm-generic/access_ok.h48
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diff --git a/include/asm-generic/access_ok.h b/include/asm-generic/access_ok.h
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+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_GENERIC_ACCESS_OK_H__
+#define __ASM_GENERIC_ACCESS_OK_H__
+
+/*
+ * Checking whether a pointer is valid for user space access.
+ * These definitions work on most architectures, but overrides can
+ * be used where necessary.
+ */
+
+/*
+ * architectures with compat tasks have a variable TASK_SIZE and should
+ * override this to a constant.
+ */
+#ifndef TASK_SIZE_MAX
+#define TASK_SIZE_MAX TASK_SIZE
+#endif
+
+#ifndef __access_ok
+/*
+ * 'size' is a compile-time constant for most callers, so optimize for
+ * this case to turn the check into a single comparison against a constant
+ * limit and catch all possible overflows.
+ * On architectures with separate user address space (m68k, s390, parisc,
+ * sparc64) or those without an MMU, this should always return true.
+ *
+ * This version was originally contributed by Jonas Bonn for the
+ * OpenRISC architecture, and was found to be the most efficient
+ * for constant 'size' and 'limit' values.
+ */
+static inline int __access_ok(const void __user *ptr, unsigned long size)
+{
+ unsigned long limit = TASK_SIZE_MAX;
+ unsigned long addr = (unsigned long)ptr;
+
+ if (IS_ENABLED(CONFIG_ALTERNATE_USER_ADDRESS_SPACE) ||
+ !IS_ENABLED(CONFIG_MMU))
+ return true;
+
+ return (size <= limit) && (addr <= (limit - size));
+}
+#endif
+
+#ifndef access_ok
+#define access_ok(addr, size) likely(__access_ok(addr, size))
+#endif
+
+#endif