[Bug 10974] New: wine prefers loopback devices over regular files

http://bugs.winehq.org/show_bug.cgi?id=10974

Summary: wine prefers loopback devices over regular files
           Product: Wine
           Version: CVS/GIT
          Platform: Other
        OS/Version: other
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: wine-kernel
        AssignedTo: [e-mail]
        ReportedBy: [e-mail]

Created an attachment (id=9920)
 --> (http://bugs.winehq.org/attachment.cgi?id=9920)
fix loopback handling

When using a loopback device as a wine drive, wine will prefer to use the
loopback device (e.g. /dev/loop0) for volume access rather than the regular
file it's based on (e.g. ~/foo.iso).
> From dlls/ntdll/directory.c:

else if (!stat( entry->mnt_fsname, &st ) && S_ISREG(st.st_mode))
        {
            /* if device is a regular file check for a loop mount */
            if ((device = strstr( entry->mnt_opts, "loop=" )))
            {
                char *p = strchr( device + 5, ',' );
                if (p) *p = 0;
                return device + 5;
            }
        }

I'm not sure if this has any advantage, but it has a big inconvenient.  It's
almost certain that /dev/loop0 is owned by root and not world-readable, and
it's also mostly certain that wine isn't being run as root.  If the image is
user-owned, by using the loop device we lose the ability to read it.

This typicaly causes breakage that is difficult to figure out.  For example,
see
http://appdb.winehq.org/objectManager.php?sClass=version&iId=727&iTe...

Note: I'm filing this separate from bug 10957 because it's an unrelated issue. 
The patch I'm attaching here collides with the one I sent for bug 10957, but
takes both situations into account.