Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938192AbcLMRXD (ORCPT ); Tue, 13 Dec 2016 12:23:03 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:57140 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936195AbcLMRQg (ORCPT ); Tue, 13 Dec 2016 12:16:36 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jeff Layton , Miklos Szeredi Subject: [PATCH 4.8 04/33] fuse: fix clearing suid, sgid for chown() Date: Tue, 13 Dec 2016 09:16:05 -0800 Message-Id: <20161213171534.346961221@linuxfoundation.org> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20161213171534.171564506@linuxfoundation.org> References: <20161213171534.171564506@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2174 Lines: 64 4.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Miklos Szeredi commit c01638f5d919728f565bf8b5e0a6a159642df0d9 upstream. Basically, the pjdfstests set the ownership of a file to 06555, and then chowns it (as root) to a new uid/gid. Prior to commit a09f99eddef4 ("fuse: fix killing s[ug]id in setattr"), fuse would send down a setattr with both the uid/gid change and a new mode. Now, it just sends down the uid/gid change. Technically this is NOTABUG, since POSIX doesn't _require_ that we clear these bits for a privileged process, but Linux (wisely) has done that and I think we don't want to change that behavior here. This is caused by the use of should_remove_suid(), which will always return 0 when the process has CAP_FSETID. In fact we really don't need to be calling should_remove_suid() at all, since we've already been indicated that we should remove the suid, we just don't want to use a (very) stale mode for that. This patch should fix the above as well as simplify the logic. Reported-by: Jeff Layton Signed-off-by: Miklos Szeredi Fixes: a09f99eddef4 ("fuse: fix killing s[ug]id in setattr") Reviewed-by: Jeff Layton Signed-off-by: Greg Kroah-Hartman --- fs/fuse/dir.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1709,8 +1709,6 @@ static int fuse_setattr(struct dentry *e return -EACCES; if (attr->ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID)) { - int kill; - attr->ia_valid &= ~(ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_MODE); /* @@ -1722,12 +1720,11 @@ static int fuse_setattr(struct dentry *e return ret; attr->ia_mode = inode->i_mode; - kill = should_remove_suid(entry); - if (kill & ATTR_KILL_SUID) { + if (inode->i_mode & S_ISUID) { attr->ia_valid |= ATTR_MODE; attr->ia_mode &= ~S_ISUID; } - if (kill & ATTR_KILL_SGID) { + if ((inode->i_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { attr->ia_valid |= ATTR_MODE; attr->ia_mode &= ~S_ISGID; }