nfsd: allow root to set uid and gid on create

The server silently ignores attempts to set the uid and gid on create.
Based on the comment, this appears to have been done to prevent some
overly-clever IRIX client from causing itself problems.

Perhaps we should remove that hack completely.  For now, at least, it
makes sense to allow root (when no_root_squash is set) to set uid and
gid.

While we're there, since nfsd_create and nfsd_create_v3 share the same
logic, pull that out into a separate function.  And spell out the
individual modifications of ia_valid instead of doing them both at once
inside a conditional.

Thanks to Roger Willcocks <roger@filmlight.ltd.uk> for the bug report
and original patch on which this is based.
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

fs/nfsd/vfs.c

@@ -1151,6 +1151,26 @@ nfsd_commit(struct svc_rqst *rqstp, struct svc_fh *fhp,
 }
 #endif /* CONFIG_NFSD_V3 */
 
+__be32
+nfsd_create_setattr(struct svc_rqst *rqstp, struct svc_fh *resfhp,
+			struct iattr *iap)
+{
+	/*
+	 * Mode has already been set earlier in create:
+	 */
+	iap->ia_valid &= ~ATTR_MODE;
+	/*
+	 * Setting uid/gid works only for root.  Irix appears to
+	 * send along the gid on create when it tries to implement
+	 * setgid directories via NFS:
+	 */
+	if (current->fsuid != 0)
+		iap->ia_valid &= ~(ATTR_UID|ATTR_GID);
+	if (iap->ia_valid)
+		return nfsd_setattr(rqstp, resfhp, iap, 0, (time_t)0);
+	return 0;
+}
+
 /*
  * Create a file (regular, directory, device, fifo); UNIX sockets 
  * not yet implemented.
@@ -1167,6 +1187,7 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	struct dentry	*dentry, *dchild = NULL;
 	struct inode	*dirp;
 	__be32		err;
+	__be32		err2;
 	int		host_err;
 
 	err = nfserr_perm;
@@ -1257,16 +1278,9 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	}
 
 
-	/* Set file attributes. Mode has already been set and
-	 * setting uid/gid works only for root. Irix appears to
-	 * send along the gid when it tries to implement setgid
-	 * directories via NFS.
-	 */
-	if ((iap->ia_valid &= ~(ATTR_UID|ATTR_GID|ATTR_MODE)) != 0) {
-		__be32 err2 = nfsd_setattr(rqstp, resfhp, iap, 0, (time_t)0);
-		if (err2)
-			err = err2;
-	}
+	err2 = nfsd_create_setattr(rqstp, resfhp, iap);
+	if (err2)
+		err = err2;
 	/*
 	 * Update the file handle to get the new inode info.
 	 */
@@ -1295,6 +1309,7 @@ nfsd_create_v3(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	struct dentry	*dentry, *dchild = NULL;
 	struct inode	*dirp;
 	__be32		err;
+	__be32		err2;
 	int		host_err;
 	__u32		v_mtime=0, v_atime=0;
 
@@ -1399,16 +1414,10 @@ nfsd_create_v3(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		iap->ia_atime.tv_nsec = 0;
 	}
 
-	/* Set file attributes.
-	 * Irix appears to send along the gid when it tries to
-	 * implement setgid directories via NFS. Clear out all that cruft.
-	 */
  set_attr:
-	if ((iap->ia_valid &= ~(ATTR_UID|ATTR_GID|ATTR_MODE)) != 0) {
- 		__be32 err2 = nfsd_setattr(rqstp, resfhp, iap, 0, (time_t)0);
-		if (err2)
-			err = err2;
-	}
+	err2 = nfsd_create_setattr(rqstp, resfhp, iap);
+	if (err2)
+		err = err2;
 
 	/*
 	 * Update the filehandle to get the new inode info.