The excompat udr functions can be used to read data from a file.
If you create a stored procedure using these and are accessing a
line, which is too long for the buffer,
this can lead to all sorts of memory corruptions.
The afs depend on which memory is overwritten, and can lead to
all sorts of errors.
One example is:
15:07:13 Found during mt_shm_malloc_segid 5, error seen 1 times
since last print to the log
15:07:13 Pool '33' (0x462ef040)
15:07:13 Bad free block 0x46446038
15:07:13 Assert Warning: Memory free block header corruption
detected in mt_shm_malloc_segid 5
15:07:13 IBM Informix Dynamic Server Version 12.10.FC14
15:07:13 Who: Session(33, user@hostname, 18142, 0x44f3a048)
Thread(61, sqlexec, 44ef6388, 1)
File: mtshpool.c Line: 1817
15:07:13 Results: Pool free list repaired
15:07:13 Action: Please notify IBM Informix Technical Support.
15:07:13 stack trace for pid 20541 written to
DUMPDIR/af.4256501
but it can also look like this:
16:58:37 IBM Informix Dynamic Server Version 12.10.FC14
16:58:37 Who: Session(26, user@hostname, 0, 0x44f3b178)
Thread(53, dbScheduler, 44ef98c8, 1)
File: mtshpool.c Line: 1834
16:58:37 Results: Pool free list not repaired
16:58:37 Action: Please notify IBM Informix Technical Support.
16:58:37 stack trace for pid 29693 written to
DUMPDIR/af.41d2d9b
16:58:37 See Also: DUMPDIR/af.41d2d9b
16:58:38 Memory free block header corruption detected in
mt_shm_malloc_segid 1
16:58:38 invoke_alarm(): /bin/sh -c
'/opt/informix/IBM/12.10.FC14n_lb/etc/alarmprogram.sh 3 6
"Internal Subsystem failure: 'MT'" "Exception Caught. Type:
MT_EX_OS, Context: mem" "" 6300'
16:58:38 invoke_alarm(): mt_exec failed, status -1, errno 0
16:58:38 (-9791): ERROR: Routine execution trap --
procname= procid=575
reason: mem
In the stored procedure utl_ifle_get_Line
CALL "informix".utl_file_get_line(lFilePointer, lString);
is used with a defined length for lString, but the line trying
to be read, is much bigger than that.
This leads to the memory being overwritten, and depending on the
memory, to all sorts of errors. |
