[MDEV-26761] main.mysql_client_test test_mdev19838 fails with MemorySanitizer Created: 2021-10-04  Updated: 2021-10-06  Resolved: 2021-10-05

Status: Closed
Project: MariaDB Server
Component/s: libmariadb, Tests
Affects Version/s: 10.5, 10.6, 10.7
Fix Version/s: 10.5.13, 10.6.5, 10.7.1

Type: Bug Priority: Major
Reporter: Marko Mäkelä Assignee: Georg Richter
Resolution: Fixed Votes: 0
Labels: MSAN

Issue Links:
Relates
relates to CONC-483 Workaround for MSAN bug needed Closed
relates to MDEV-19838 mariadb odbc driver 3.1.1-ga sometime... Closed
relates to MDEV-26758 Make libmariadb run under MSAN Closed

 Description   

This came up while I was working on MDEV-26758. These tests used to fail with MemorySanitizer:

main.mysql_client_test_comp              w3 [ pass ]  43767
 
main.mysql_client_test_nonblock          w2 [ pass ]  44749
 
main.mysql_client_test                   w1 [ pass ]  44743

I suspect that fixing test_mdev19838() requires some changes in libmariadb itself. I am getting the following trace:

==WARNING: MemorySanitizer: use-of-uninitialized-value
 
    #0 0x55f050b09636 in madb_reset_stmt /mariadb/10.5m/libmariadb/libmariadb/mariadb_stmt.c:2159:15
 
    #1 0x55f050b04e7e in mysql_stmt_internal_reset /mariadb/10.5m/libmariadb/libmariadb/mariadb_stmt.c:2186:8
 
    #2 0x55f050b075e3 in mysql_stmt_close /mariadb/10.5m/libmariadb/libmariadb/mariadb_stmt.c:1400:7
 
    #3 0x55f050ac9524 in wrap_mysql_stmt_close /mariadb/10.5m/tests/nonblock-wrappers.h:369:1
 
    #4 0x55f050ac9524 in test_mdev19838 /mariadb/10.5m/tests/mysql_client_test.c:21259:5
 
    #5 0x55f05085e978 in main /mariadb/10.5m/tests/mysql_client_fw.c:1449:9
 
    #6 0x7f04193f1e49 in __libc_start_main csu/../csu/libc-start.c:314:16
 
    #7 0x55f0507d5869 in _start (/dev/shm/10.5msan/tests/mariadb-client-test+0x5b869)
 
 
 
  Uninitialized value was created by a heap allocation
 
    #0 0x55f0507e1cad in malloc (/dev/shm/10.5msan/tests/mariadb-client-test+0x67cad)
 
    #1 0x55f050af8a0c in ma_init_alloc_root /mariadb/10.5m/libmariadb/libmariadb/ma_alloc.c:36:18

For now, I will disable test_mdev19838() under MemorySanitizer. It was already disabled for the embedded server.

 Comments   
Comment by Marko Mäkelä [ 2021-10-05 ]

For what it is worth, also this simpler fix would seem to have fixed the issue for me:

diff --git a/libmariadb/mariadb_stmt.c b/libmariadb/mariadb_stmt.c
 
index 516b801..b56ac9f 100644
 
--- a/libmariadb/mariadb_stmt.c
 
+++ b/libmariadb/mariadb_stmt.c
 
@@ -2207,8 +2207,7 @@ static my_bool madb_reset_stmt(MYSQL_STMT *stmt, unsigned int flags)
 
       {
 
         ulonglong i;
 
         for (i=0; i < stmt->param_count; i++)
 
-          if (stmt->params[i].long_data_used)
 
-            stmt->params[i].long_data_used= 0;
 
+          stmt->params[i].long_data_used= 0;
 
       }
 
     }

I tested the fix on 10.5 and 10.6 and updated libmariadb on both.

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