PQ54213: FTP MAY OVERLAY STORAGE WHEN READING A RECFM=F OR FB DATA SET WITH A BLKSIZE THAT IS NOT A MULTIPLE OF THE LRECL

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• FTP client or server may write data outside of its buffer when
  processing a recfm=f file whose block size is not a multiple
  of the lrecl.  FTP is trying to send this file in ASCII mode.
  It has entered routine read_ascii_as_image and determines how
  many records it can fit in its buffer, after adding the CRLF for
  end of record.  It does this by dividing the blocksize by the
  lrecl, then multiplying by the lrecl+2.  It then instructs BSAM
  to read this many blocks of data.  However, when it tries to
  remove blanks for the dataset and insert the CRLF into the data
  it moves the data a lrecl at a time.  The block contains extra
  data that is not fully contained in a lrecl.  Thus, FTP moves
  more records than it calculated it would, overlaying the
  buffer.  The FTP server may overlay CSA data.  The FTP client
  will abend 0c4 in read_ascii_as_image, on a IC instruction.
  .
  ADDITIONAL SYMPTOMS:
  .
  VERIFICATION STEPS:
  1) FTP will be transferring a dataset with a block size that is
     not a multiple of the lrecl.
  2) FTP server trace may show sendx_data trace records with a
     size greater than 180K.
  .
  KEYWORDS:
  CSA CSM 180K overlay abend0c4 0c4 s0c4
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of the Communications Server for   *
  *                 OS/390 Release 8 & 10 IP and z/OS            *
  *                 Version 1 Release 2 : FTP                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: Storage overlay when transferring an    *
  *                      MVS data set with RECFM=FB, BLKSIZE     *
  *                      not a multiple of LRECL, type ASCII,    *
  *                      and mode stream.                        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  If the routine that handles fastio transfer for FB data sets
  with ASCII data encounters a data set where the BLKSIZE is not
  a valid multiple of the LRECL, the output buffer can be overrun
  while trying to process the leftover data in the input block.
  If this occurs in the FTP Server, the overlay can occur in ECSA
  and cause a system outage.
  +-------------------------------------------------------------+
  + Please check our Communications Server for OS/390 homepages +
  + for common networking tips and fixes.  The URL for these    +
  + homepages can be found in Informational APAR II11334.       +
  +-------------------------------------------------------------+
  

Problem conclusion

• The routine that handles fastio for ASCII FB data sets has been
  changed to detect the potential for a storage overlay (write
  past the end of the buffer) and return an error instead.
  
  If the invalid input file is being read in the FTP Server (GET),
  the following reply will be sent to the client:
  
        451 Transfer aborted: file error.
  
  If the invalid input file is being read in the FTP Client (PUT),
  the following message is displayed at the client:
  
        EZA2602E Error reading the file
  
  
  * Cross Reference between External and Internal Names
  PREFTPCX (EZAFTPCX)  PREFTPLS (EZAFTPLS)  PREFTPCX (EZAFTPCX)
  PREFTPLS (EZAFTPLS)  PREFTPCX (EZAFTPCX)  PREFTPLS (EZAFTPLS)
  

Temporary fix

• *********
  * HIPER *
  *********
  
  APPLY ++APAR RELIEF IF NEEDED.
  

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  UQ60601 UQ60602 UQ60603

Modules/Macros

• EZAFTPCX EZAFTPLS EZAFTPTO
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R120 PSY UQ60601

     UP01/12/26 P F112 Ž

• R380 PSY UQ60602

     UP01/12/26 P F112 Ž

• R50A PSY UQ60603

     UP01/12/26 P F112 Ž

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.