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[Laurynas Biveinis <laurynas.biveinis@xxxxxxxxx>]

Public bug reported:

Copy of

[13 Aug 16:21] Laurynas Biveinis
Description:
recv_parse_log_rec is documented as follows:

** Tries to parse a single log record.
...
@param[in]      ptr             pointer to a buffer
@param[in]      end_ptr         end of the buffer
...
@return length of the record, or 0 if the record was not complete */

The record is complete if its length <= end_ptr - ptr, in which case
length is returned, otherwise the record is incomplete and zero is
returned. This is true for all the record types except for
MLOG_CHECKPOINT, for which SIZE_OF_MLOG_CHECKPOINT is returned
regardless of end_ptr - ptr. Then the caller handles the incomplete
record case itself. This could be a problem for patches that reuse
recv_parse_log_rec for something else.

A uniform incomplete record handling regardless of the record type would
be cleaner.

This state of things could be a result of MLOG_CHECKPOINT being one-byte
record originally, and handled as other one byte records in this
function.

How to repeat:
Code analysis.

Suggested fix:
@@ -2338,7 +2349,8 @@ recv_parse_log_rec(
                return(1);
        case MLOG_CHECKPOINT:
                *type = static_cast<mlog_id_t>(*ptr);
-               return(SIZE_OF_MLOG_CHECKPOINT);
+               return ((end_ptr - ptr < SIZE_OF_MLOG_CHECKPOINT)
+                       ? 0 : SIZE_OF_MLOG_CHECKPOINT);
        case MLOG_MULTI_REC_END | MLOG_SINGLE_REC_FLAG:
        case MLOG_DUMMY_RECORD | MLOG_SINGLE_REC_FLAG:
        case MLOG_CHECKPOINT | MLOG_SINGLE_REC_FLAG:
@@ -2563,9 +2575,6 @@ loop:
                        /* Do nothing */
                        break;
                case MLOG_CHECKPOINT:
-                       if (end_ptr < ptr + SIZE_OF_MLOG_CHECKPOINT) {
-                               return(false);
-                       }
 #if SIZE_OF_MLOG_CHECKPOINT != 1 + 8
 # error SIZE_OF_MLOG_CHECKPOINT != 1 + 8
 #endif

** Affects: mysql-server
     Importance: Unknown
         Status: Unknown

** Affects: percona-server
     Importance: Undecided
         Status: Invalid

** Affects: percona-server/5.1
     Importance: Undecided
         Status: Invalid

** Affects: percona-server/5.5
     Importance: Undecided
         Status: Invalid

** Affects: percona-server/5.6
     Importance: Undecided
         Status: Invalid

** Affects: percona-server/5.7
     Importance: Medium
     Assignee: Laurynas Biveinis (laurynas-biveinis)
         Status: Fix Committed


** Tags: upstream

** Also affects: percona-server/5.7
   Importance: Undecided
       Status: New

** Also affects: percona-server/5.5
   Importance: Undecided
       Status: New

** Also affects: percona-server/5.1
   Importance: Undecided
       Status: New

** Also affects: percona-server/5.6
   Importance: Undecided
       Status: New

** Changed in: percona-server/5.1
       Status: New => Invalid

** Changed in: percona-server/5.5
       Status: New => Invalid

** Changed in: percona-server/5.6
       Status: New => Invalid

** Changed in: percona-server/5.7
     Assignee: (unassigned) => Laurynas Biveinis (laurynas-biveinis)

** Changed in: percona-server/5.7
   Importance: Undecided => Medium

** Changed in: percona-server/5.7
       Status: New => Fix Committed

** Tags added: upstream

** Bug watch added: MySQL Bug System #78058
   http://bugs.mysql.com/bug.php?id=78058

** Also affects: mysql-server via
   http://bugs.mysql.com/bug.php?id=78058
   Importance: Unknown
       Status: Unknown

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https://bugs.launchpad.net/bugs/1484599

Title:
  recv_parse_log_rec violates its contract re. incomplete recs for
  MLOG_CHECKPOINT

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