MDEV-20917 InnoDB is passing NULL to nonnull function parameters

mem_heap_dup(): Avoid mem_heap_alloc() and memcpy() of data=NULL, len=0.

trx_undo_report_insert_virtual(), trx_undo_page_report_insert(),
trx_undo_page_report_modify(): Avoid memcpy(ptr, NULL, 0).

dfield_data_is_binary_equal(): Correctly handle data=NULL, len=0.

rec_init_offsets_temp(): Do allow def_val=NULL in the interface.

This clean-up was motivated by WITH_UBSAN, and no bug related to this
was observed in the wild. It should be noted that undefined behaviour
such as memcpy(ptr, NULL, 0) could allow compilers to perform unsafe
optimizations, like it was the case in
commit fc168c3a (MDEV-15587).

storage/innobase/include/data0data.h

@@ -168,7 +168,7 @@ dfield_data_is_binary_equal(
 	const dfield_t*	field,	/*!< in: field */
 	ulint		len,	/*!< in: data length or UNIV_SQL_NULL */
 	const byte*	data)	/*!< in: data */
-	MY_ATTRIBUTE((nonnull, warn_unused_result));
+	MY_ATTRIBUTE((nonnull(1), warn_unused_result));
 
 /*********************************************************************//**
 Gets info bits in a data tuple.

storage/innobase/include/data0data.ic

@@ -225,7 +225,7 @@ dfield_data_is_binary_equal(
 {
 	ut_ad(len != UNIV_SQL_DEFAULT);
 	return(len == dfield_get_len(field)
-	       && (len == UNIV_SQL_NULL
+	       && (!len || len == UNIV_SQL_NULL
 		   || !memcmp(dfield_get_data(field), data, len)));
 }
 

storage/innobase/include/mem0mem.h

@@ -237,7 +237,10 @@ inline
 void*
 mem_heap_dup(mem_heap_t* heap, const void* data, size_t len)
 {
-	return(memcpy(mem_heap_alloc(heap, len), data, len));
+	ut_ad(data || !len);
+	return UNIV_LIKELY(data != NULL)
+		? memcpy(mem_heap_alloc(heap, len), data, len)
+		: NULL;
 }
 
 /** Duplicate a NUL-terminated string, allocated from a memory heap.

storage/innobase/include/rem0rec.h

@@ -983,7 +983,7 @@ rec_init_offsets_temp(
 	ulint			n_core,
 	const dict_col_t::def_t*def_val,
 	rec_comp_status_t	status = REC_STATUS_ORDINARY)
-	MY_ATTRIBUTE((nonnull));
+	MY_ATTRIBUTE((nonnull(1,2,3)));
 /** Determine the offset to each field in temporary file.
 @param[in]	rec	temporary file record
 @param[in]	index	index of that the record belongs to

storage/innobase/mem/mem0mem.cc

 /*****************************************************************************
 
 Copyright (c) 1994, 2014, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, 2018, MariaDB Corporation.
+Copyright (c) 2017, 2019, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software

storage/innobase/trx/trx0rec.cc

@@ -421,9 +421,15 @@ trx_undo_report_insert_virtual(
 
 			const dfield_t* vfield = dtuple_get_nth_v_field(
 				row, col->v_pos);
-			ulint	flen = vfield->len;
+			switch (ulint flen = vfield->len) {
+			case 0: case UNIV_SQL_NULL:
+				if (trx_undo_left(undo_block, *ptr) < 5) {
+					return(false);
+				}
 
-			if (flen != UNIV_SQL_NULL) {
+				*ptr += mach_write_compressed(*ptr, flen);
+				break;
+			default:
 				ulint	max_len
 					= dict_max_v_field_len_store_undo(
 						table, col_no);
@@ -438,14 +444,8 @@ trx_undo_report_insert_virtual(
 				}
 				*ptr += mach_write_compressed(*ptr, flen);
 
-				ut_memcpy(*ptr, vfield->data, flen);
+				memcpy(*ptr, vfield->data, flen);
 				*ptr += flen;
-			} else {
-				if (trx_undo_left(undo_block, *ptr) < 5) {
-					return(false);
-				}
-
-				*ptr += mach_write_compressed(*ptr, flen);
 			}
 		}
 	}
@@ -524,13 +524,16 @@ trx_undo_page_report_insert(
 
 		ptr += mach_write_compressed(ptr, flen);
 
-		if (flen != UNIV_SQL_NULL) {
+		switch (flen) {
+		case 0: case UNIV_SQL_NULL:
+			break;
+		default:
 			if (trx_undo_left(undo_block, ptr) < flen) {
 
 				return(0);
 			}
 
-			ut_memcpy(ptr, dfield_get_data(field), flen);
+			memcpy(ptr, dfield_get_data(field), flen);
 			ptr += flen;
 		}
 	}
@@ -998,7 +1001,7 @@ trx_undo_page_report_modify(
 				return(0);
 			}
 
-			ut_memcpy(ptr, field, flen);
+			memcpy(ptr, field, flen);
 			ptr += flen;
 		}
 	}
@@ -1129,7 +1132,7 @@ trx_undo_page_report_modify(
 					return(0);
 				}
 
-				ut_memcpy(ptr, field, flen);
+				memcpy(ptr, field, flen);
 				ptr += flen;
 			}
 
@@ -1154,7 +1157,7 @@ trx_undo_page_report_modify(
 						return(0);
 					}
 
-					ut_memcpy(ptr, field, flen);
+					memcpy(ptr, field, flen);
 					ptr += flen;
 				}
 			}
@@ -1303,7 +1306,7 @@ trx_undo_page_report_modify(
 						return(0);
 					}
 
-					ut_memcpy(ptr, field, flen);
+					memcpy(ptr, field, flen);
 					ptr += flen;
 				}
 
@@ -1388,13 +1391,16 @@ trx_undo_page_report_modify(
 
 				ptr += mach_write_compressed(ptr, flen);
 
-				if (flen != UNIV_SQL_NULL) {
+				switch (flen) {
+				case 0: case UNIV_SQL_NULL:
+					break;
+				default:
 					if (trx_undo_left(undo_block, ptr)
 					    < flen) {
 						return(0);
 					}
 
-					ut_memcpy(ptr, field, flen);
+					memcpy(ptr, field, flen);
 					ptr += flen;
 				}
 			}