+
+/**
+ * strncpy_from_unsafe_user: - Copy a NUL terminated string from unsafe user
+ * address.
+ * @dst: Destination address, in kernel space. This buffer must be at
+ * least @count bytes long.
+ * @unsafe_addr: Unsafe user address.
+ * @count: Maximum number of bytes to copy, including the trailing NUL.
+ *
+ * Copies a NUL-terminated string from unsafe user address to kernel buffer.
+ *
+ * On success, returns the length of the string INCLUDING the trailing NUL.
+ *
+ * If access fails, returns -EFAULT (some data may have been copied
+ * and the trailing NUL added).
+ *
+ * If @count is smaller than the length of the string, copies @count-1 bytes,
+ * sets the last byte of @dst buffer to NUL and returns @count.
+ */
+long strncpy_from_unsafe_user(char *dst, const void __user *unsafe_addr,
+ long count)
+{
+ mm_segment_t old_fs = get_fs();
+ long ret;
+
+ if (unlikely(count <= 0))
+ return 0;
+
+ set_fs(USER_DS);
+ pagefault_disable();
+ ret = strncpy_from_user(dst, unsafe_addr, count);
+ pagefault_enable();
+ set_fs(old_fs);
+
+ if (ret >= count) {
+ ret = count;
+ dst[ret - 1] = '\0';
+ } else if (ret > 0) {
+ ret++;
+ }
+
+ return ret;
+}
+
+/**
+ * strnlen_unsafe_user: - Get the size of a user string INCLUDING final NUL.
+ * @unsafe_addr: The string to measure.
+ * @count: Maximum count (including NUL)
+ *
+ * Get the size of a NUL-terminated string in user space without pagefault.
+ *
+ * Returns the size of the string INCLUDING the terminating NUL.
+ *
+ * If the string is too long, returns a number larger than @count. User
+ * has to check the return value against "> count".
+ * On exception (or invalid count), returns 0.
+ *
+ * Unlike strnlen_user, this can be used from IRQ handler etc. because
+ * it disables pagefaults.
+ */
+long strnlen_unsafe_user(const void __user *unsafe_addr, long count)
+{
+ mm_segment_t old_fs = get_fs();
+ int ret;
+
+ set_fs(USER_DS);
+ pagefault_disable();
+ ret = strnlen_user(unsafe_addr, count);
+ pagefault_enable();
+ set_fs(old_fs);
+
+ return ret;
+}