rsync - Oct 2007 - DO NOT REPLY [Bug 5027] New: Perms in do_mkstemp are not always valid

https://bugzilla.samba.org/show_bug.cgi?id=5027

           Summary: Perms in do_mkstemp are not always valid
           Product: rsync
           Version: 2.6.9
          Platform: x86
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: core
        AssignedTo: wayned@samba.org
        ReportedBy: cmadams@hiwaay.net
         QAContact: rsync-qa@samba.org


I'm trying to rsync (with -a to preserve permissions) to a mount point on an
NFS server, and it fails when copying a file that is read-only.  The problem is
that do_mkstemp creates the temp file with the desired user permissions (either
with open() or with fchmod().

SUSv3 says that the affect of chmod()/fchmod() on existing open file
descriptors is implemtation defined; it also says:

    Any file descriptors currently open by any process on the file could
    possibly become invalid if the mode of the file is changed to a value which
    would deny access to that process. One situation where this could occur is
    on a stateless file system. This behavior will not occur in a conforming
    environment.

I guess I have a non-conforming environment (I'm talking to a unfs3 server).

If I remove HAVE_FCHMOD, it still doesn't work, because the call to open()
includes the read-only permissions as well (a case I don't really see
referenced in SUSv3 right off).

The following patch makes sure that the user always has write permission to the
temp file:

diff -urN rsync-2.6.9-dist/syscall.c rsync-2.6.9/syscall.c
--- rsync-2.6.9-dist/syscall.c  2007-10-19 20:49:29.000000000 -0500
+++ rsync-2.6.9/syscall.c       2007-10-19 20:53:02.000000000 -0500
@@ -190,6 +190,7 @@
 {
        RETURN_ERROR_IF(dry_run, 0);
        RETURN_ERROR_IF(read_only, EROFS);
+       perms |= S_IWUSR;

 #if defined HAVE_SECURE_MKSTEMP && defined HAVE_FCHMOD &&
(!defined
HAVE_OPEN64 || defined HAVE_MKSTEMP64)
        {


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https://bugzilla.samba.org/show_bug.cgi?id=5027





------- Comment #1 from cmadams@hiwaay.net  2007-10-19 21:01 CST -------
Created an attachment (id=2947)
 --> (https://bugzilla.samba.org/attachment.cgi?id=2947&action=view)
Make sure the user has write permission to the temp file


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https://bugzilla.samba.org/show_bug.cgi?id=5027


wayned@samba.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED




------- Comment #2 from wayned@samba.org  2007-11-03 14:30 CST -------
I checked that the callers of do_mkstemp() will all fix the permissions if the
user-write permission is not supposed to be on final file, and it looks good. 
I've checked your patch into CVS.  Thanks!


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