The Samba-Bugzilla – Bug 5027
Perms in do_mkstemp are not always valid
Last modified: 2007-11-03 14:30:44 UTC
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
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 @@
+ perms |= S_IWUSR;
#if defined HAVE_SECURE_MKSTEMP && defined HAVE_FCHMOD && (!defined HAVE_OPEN64 || defined HAVE_MKSTEMP64)
Created attachment 2947 [details]
Make sure the user has write permission to the temp file
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!