RE: possible loss of data due to missing close when --stdout in force

[Giuliano.Procida]

I wrote:

> The bad code is in gzip.c:
> 
>     if (!to_stdout)
>       {
>         sigset_t oldset;
>         int unlink_errno;
> 
>         copy_stat (&istat);
>         if (close (ofd) != 0)
>           write_error ();

However, the close will need to occur after the last file has been written to 
stdout, perhaps in main itself. Alternatively, you could dup stdout for each 
file and close the duplicate (would this work)?

Regards,
Giuliano Procida.

-----Original Message-----
From: Procida, Giuliano 
Sent: 27 January 2009 12:19
To: 'address@hidden'
Subject: possible loss of data due to missing close when --stdout in force

Hi.

Tested gzip 1.3.3 and 1.3.12 on Linux i386.

When operating with --stdout, gzip fails to close stdout at the end of input. 

This can result in silent loss of data if a partition fills, with the 
probability of silent loss increasing as the size of file decreases.

I've reported the same bug in bzip2 to the author - this one did cause me 
serious problems.

The bad code is in gzip.c:

    if (!to_stdout)
      {
        sigset_t oldset;
        int unlink_errno;

        copy_stat (&istat);
        if (close (ofd) != 0)
          write_error ();

        sigprocmask (SIG_BLOCK, &caught_signals, &oldset);
        remove_ofname_fd = -1;
        unlink_errno = xunlink (ifname) == 0 ? 0 : errno;
        sigprocmask (SIG_SETMASK, &oldset, NULL);

        if (unlink_errno)
          {
            WARN ((stderr, "%s: ", program_name));
            if (!quiet)
              {
                errno = unlink_errno;
                perror (ifname);
              }
          }

The close and error check should happen regardless.

Regards,
Giuliano Procida.

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