MDEV-21993 asan failure in encryption.innochecksum

simplify fix

field_ref_zero: make bigger

buf_is_zeroes(): remove a loop and check in one go

storage/innobase/buf/buf0buf.cc

@@ -958,14 +958,8 @@ static uint32_t buf_page_check_crc32(const byte* page, uint32_t checksum)
 @return whether the buffer is all zeroes */
 bool buf_is_zeroes(span<const byte> buf)
 {
-  static const byte zeroes[4 * 1024] = {0};
-  for (size_t i = 0; i < buf.size(); i += std::min(sizeof(zeroes),
-						   buf.size() - i)) {
-    if (memcmp(zeroes, buf.data() + i, std::min(sizeof(zeroes),
-						buf.size() - i)) != 0)
-      return false;
-  }
-  return true;
+  ut_ad(buf.size() <= sizeof field_ref_zero);
+  return memcmp(buf.data(), field_ref_zero, buf.size()) == 0;
 }
 
 /** Check if a page is corrupt.

storage/innobase/include/page0size.h

@@ -34,7 +34,7 @@ Created Nov 14, 2013 Vasil Dimov
 /** A BLOB field reference full of zero, for use in assertions and
 tests.Initially, BLOB field references are set to zero, in
 dtuple_convert_big_rec(). */
-extern const byte field_ref_zero[FIELD_REF_SIZE];
+extern const byte field_ref_zero[UNIV_PAGE_SIZE_MAX];
 
 #define PAGE_SIZE_T_SIZE_BITS	17
 

storage/innobase/page/page0zip.cc

@@ -34,12 +34,8 @@ using st_::span;
 /** A BLOB field reference full of zero, for use in assertions and tests.
 Initially, BLOB field references are set to zero, in
 dtuple_convert_big_rec(). */
-const byte field_ref_zero[FIELD_REF_SIZE] = {
-        0, 0, 0, 0, 0,
-        0, 0, 0, 0, 0,
-        0, 0, 0, 0, 0,
-        0, 0, 0, 0, 0,
-};
+MY_ALIGNED(UNIV_PAGE_SIZE_MAX)
+const byte field_ref_zero[UNIV_PAGE_SIZE_MAX] = { 0, };
 
 #ifndef UNIV_INNOCHECKSUM
 #include "page0page.h"
@@ -113,7 +109,7 @@ Compare at most sizeof(field_ref_zero) bytes.
 /** Assert that a BLOB pointer is filled with zero bytes.
 @param b in: BLOB pointer */
 #define ASSERT_ZERO_BLOB(b) \
-	ut_ad(!memcmp(b, field_ref_zero, sizeof field_ref_zero))
+	ut_ad(!memcmp(b, field_ref_zero, FIELD_REF_SIZE))
 
 /* Enable some extra debugging output.  This code can be enabled
 independently of any UNIV_ debugging conditions. */