PERFORCE change 144766 for review

[Edward Tomasz Napierala]

http://perforce.freebsd.org/chv.cgi?CH=144766

Change 144766 by trasz at trasz_traszkan on 2008/07/06 08:57:32

	With NFS4 ACLs, it is possible that applying a mode to an ACL which
	is identical to the mode computed from that ACL will modify the ACL.
	For example, mode computed from the following ACL is 0600:
	
	       user:kamila:rwx--------C--:------:allow
		    owner@:--x-----------:------:deny
		    owner@:rw-p---A-W-Co-:------:allow
		    group@:rwxp----------:------:deny
		    group@:--------------:------:allow
		 everyone@:rwxp---A-W-Co-:------:deny
		 everyone@:------a-R-c--s:------:allow
	
	However, applying that mode (chmod 0600) changes the ACL into this:
	
	       user:kamila:rwx-----------:------:deny
	       user:kamila:rwx--------C--:------:allow
		    owner@:--x-----------:------:deny
		    owner@:rw-p---A-W-Co-:------:allow
		    group@:rwxp----------:------:deny
		    group@:--------------:------:allow
		 everyone@:rwxp---A-W-Co-:------:deny
		 everyone@:------a-R-c--s:------:allow
	
	In chmod(1) utility, there is an optimisation, which makes it not
	call chmod(2) if the mode of the file is the same as the new mode.
	Disable that optimisation for files which may have NFS4 ACLs.

Affected files ...

.. //depot/projects/soc2008/trasz_nfs4acl/TODO#5 edit
.. //depot/projects/soc2008/trasz_nfs4acl/bin/chmod/chmod.c#2 edit

Differences ...

==== //depot/projects/soc2008/trasz_nfs4acl/TODO#5 (text+ko) ====

@@ -6,10 +6,6 @@
 
 - Add error checking to acl_to_text_nfs4.c.
 
-- Find out what to do with chmod(1).  Right now, "chmod 600" on file
-  which already has mode 0600 does not call chmod(2) at all - and it
-  should, as it might cause ACL recomputation.
-
 - Make access control more granular.
 
 - Attach ZFS to the framework.

==== //depot/projects/soc2008/trasz_nfs4acl/bin/chmod/chmod.c#2 (text+ko) ====

@@ -54,6 +54,7 @@
 #include <unistd.h>
 
 void usage(void);
+int may_have_nfs4acl(const FTSENT *ent);
 
 int
 main(int argc, char *argv[])
@@ -180,8 +181,15 @@
 			break;
 		}
 		newmode = getmode(set, p->fts_statp->st_mode);
-		if ((newmode & ALLPERMS) == (p->fts_statp->st_mode & ALLPERMS))
-			continue;
+		/*
+		 * With NFS4 ACLs, it is possible that applying a mode
+		 * identical to the one computed from an ACL will change
+		 * that ACL.
+		 */
+		if (may_have_nfs4acl(p) == 0) {
+			if ((newmode & ALLPERMS) == (p->fts_statp->st_mode & ALLPERMS))
+				continue;
+		}
 		if ((*change_mode)(p->fts_accpath, newmode) && !fflag) {
 			warn("%s", p->fts_path);
 			rval = 1;
@@ -219,3 +227,25 @@
 	    "usage: chmod [-fhv] [-R [-H | -L | -P]] mode file ...\n");
 	exit(1);
 }
+
+int
+may_have_nfs4acl(const FTSENT *ent)
+{
+	int ret;
+	static dev_t previous_dev = (dev_t)-1;
+	static int supports_acls = -1;
+
+	if (previous_dev != ent->fts_statp->st_dev) {
+		previous_dev = ent->fts_statp->st_dev;
+		supports_acls = 0;
+
+		ret = pathconf(ent->fts_accpath, _PC_EXTENDED_SECURITY_NP);
+		if (ret > 0)
+			supports_acls = 1;
+		else if (ret < 0 && errno != EINVAL)
+			warn("%s", ent->fts_path);
+	}
+
+	return (supports_acls);
+}
+