[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <54BFB1B7.4020402@tycho.nsa.gov>
Date: Wed, 21 Jan 2015 09:03:35 -0500
From: Stephen Smalley <sds@...ho.nsa.gov>
To: James Morris <jmorris@...ei.org>, Ben Hutchings <ben@...adent.org.uk>
CC: Alexander Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org,
linux-security-module@...r.kernel.org,
LKML <linux-kernel@...r.kernel.org>, 770492@...s.debian.org,
Ben Harris <bjh21@....ac.uk>, oss-security@...ts.openwall.com,
John Johansen <john.johansen@...onical.com>,
Paul Moore <paul@...l-moore.com>,
Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [RFC PATCH RESEND] vfs: Move security_inode_killpriv() after
permission checks
On 01/20/2015 06:17 PM, James Morris wrote:
> On Sat, 17 Jan 2015, Ben Hutchings wrote:
>
>> chown() and write() should clear all privilege attributes on
>> a file - setuid, setgid, setcap and any other extended
>> privilege attributes.
>>
>> However, any attributes beyond setuid and setgid are managed by the
>> LSM and not directly by the filesystem, so they cannot be set along
>> with the other attributes.
>>
>> Currently we call security_inode_killpriv() in notify_change(),
>> but in case of a chown() this is too early - we have not called
>> inode_change_ok() or made any filesystem-specific permission/sanity
>> checks.
>>
>> Add a new function setattr_killpriv() which calls
>> security_inode_killpriv() if necessary, and change the setattr()
>> implementation to call this in each filesystem that supports xattrs.
>> This assumes that extended privilege attributes are always stored in
>> xattrs.
>
> It'd be useful to get some input from LSM module maintainers on this.
>
> e.g. doesn't SELinux already handle this via policy directives?
There have been a couple postings of a similar patch set [1] by Jan
Kara, although I don't believe that series addressed chown().
If I am reading the patches correctly, they (correctly) don't affect
SELinux or Smack labels; they are just calling the existing
security_inode_killpriv() hook, which is only implemented for the
capability module to remove the security.capability xattr.
[1] http://marc.info/?l=linux-security-module&m=141890696325054&w=2
Powered by blists - more mailing lists
Please check out the
Open Source Software Security Wiki, which is counterpart to this
mailing list.
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
