From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vk0-f68.google.com ([209.85.213.68]:33566 "EHLO mail-vk0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933021AbdC2VgS (ORCPT ); Wed, 29 Mar 2017 17:36:18 -0400 Received: by mail-vk0-f68.google.com with SMTP id j137so4215833vke.0 for ; Wed, 29 Mar 2017 14:36:17 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <1489166058-11789-1-git-send-email-sds@tycho.nsa.gov> From: Paul Moore Date: Wed, 29 Mar 2017 17:36:16 -0400 Message-ID: Subject: Re: [PATCH] fs: switch order of CAP_DAC_OVERRIDE and CAP_DAC_READ_SEARCH checks To: Stephen Smalley , viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org Cc: James Morris , serge@hallyn.com, john.johansen@canonical.com, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov Content-Type: text/plain; charset=UTF-8 Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Fri, Mar 10, 2017 at 2:54 PM, Paul Moore wrote: > On Fri, Mar 10, 2017 at 12:14 PM, Stephen Smalley wrote: >> generic_permission() presently checks CAP_DAC_OVERRIDE prior to >> CAP_DAC_READ_SEARCH. This can cause misleading audit messages when >> using a LSM such as SELinux or AppArmor, since CAP_DAC_OVERRIDE >> may not be required for the operation. Flip the order of the >> tests so that CAP_DAC_OVERRIDE is only checked when required for >> the operation. >> >> Signed-off-by: Stephen Smalley >> --- >> fs/namei.c | 20 ++++++++++---------- >> 1 file changed, 10 insertions(+), 10 deletions(-) > > This is the second posting of this patch and so far no comment ... if > I don't see any negative responses by next week I'll go ahead and > merge this into the selinux/next tree. No objections, but plenty of ACKs and Reviewed-bys so I just merged this into the selinux/next tree. Thanks all. >> diff --git a/fs/namei.c b/fs/namei.c >> index d41fab7..482414a 100644 >> --- a/fs/namei.c >> +++ b/fs/namei.c >> @@ -340,22 +340,14 @@ int generic_permission(struct inode *inode, int mask) >> >> if (S_ISDIR(inode->i_mode)) { >> /* DACs are overridable for directories */ >> - if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) >> - return 0; >> if (!(mask & MAY_WRITE)) >> if (capable_wrt_inode_uidgid(inode, >> CAP_DAC_READ_SEARCH)) >> return 0; >> - return -EACCES; >> - } >> - /* >> - * Read/write DACs are always overridable. >> - * Executable DACs are overridable when there is >> - * at least one exec bit set. >> - */ >> - if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO)) >> if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) >> return 0; >> + return -EACCES; >> + } >> >> /* >> * Searching includes executable on directories, else just read. >> @@ -364,6 +356,14 @@ int generic_permission(struct inode *inode, int mask) >> if (mask == MAY_READ) >> if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH)) >> return 0; >> + /* >> + * Read/write DACs are always overridable. >> + * Executable DACs are overridable when there is >> + * at least one exec bit set. >> + */ >> + if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO)) >> + if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) >> + return 0; >> >> return -EACCES; >> } >> -- >> 2.7.4 >> > > > > -- > paul moore > www.paul-moore.com -- paul moore www.paul-moore.com