From: David Howells <dhowells@redhat.com>
To: Stephen Smalley <sds@tycho.nsa.gov>
Cc: dhowells@redhat.com, linux-unionfs@vger.kernel.org,
selinux@tycho.nsa.gov, linux-fsdevel@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org, drquigl <drquigl@tycho.nsa.gov>,
Eric Paris <eparis@parisplace.org>
Subject: Re: [PATCH 5/7] SELinux: Handle opening of a unioned file
Date: Tue, 16 Jun 2015 17:49:48 +0100 [thread overview]
Message-ID: <7332.1434473388@warthog.procyon.org.uk> (raw)
In-Reply-To: <557ECBC5.7000705@tycho.nsa.gov>
Stephen Smalley <sds@tycho.nsa.gov> wrote:
> It looks like commit 415103f9932d45f7927f4b17e3a9a13834cdb9a1 changed
> selinux_inode_init_security()'s handling of SECURITY_FS_USE_MNTPOINT,
> and this change was never propagated to selinux_dentry_init_security().
> However, that commit also did not update
> security/selinux/hooks.c:may_create()'s logic for computing the new file
> label when checking CREATE permission, and therefore introduced a
> potential inconsistency between the label used for the permission check
> and the label assigned to the inode.
>
> That's why I suggested that we need a common helper for all three to
> ensure consistency there.
I think a common helper is harder than it seems. We need the parent dir in
one of the cases the helper has to consider, but finding it is done in three
different ways, depending on the caller:
(1) dentry_init can just use ->d_parent as there's a lock held that prevents
it changing (I think). This could use (2) instead, however.
(2) file_open has to use dget_parent().
(3) inode_init doesn't have any dentries, but rather has the object and
parent inodes.
If we don't mind file_open() always calling dget_parent(), then the common
helper can take the dir inode.
Also, thinking ahead to the possibility of bringing unionmount into the kernel
at some point: union non-dir dentries that are not yet copied up have no inode
attached, but rather fall through to the underlying lower inode in the VFS.
This, however, gives us nowhere to hang the inode label. How expensive is the
security_transition_sid() call?
David
WARNING: multiple messages have this Message-ID (diff)
From: David Howells <dhowells@redhat.com>
To: Stephen Smalley <sds@tycho.nsa.gov>
Cc: linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org,
dhowells@redhat.com, drquigl <drquigl@tycho.nsa.gov>,
linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 5/7] SELinux: Handle opening of a unioned file
Date: Tue, 16 Jun 2015 17:49:48 +0100 [thread overview]
Message-ID: <7332.1434473388@warthog.procyon.org.uk> (raw)
In-Reply-To: <557ECBC5.7000705@tycho.nsa.gov>
Stephen Smalley <sds@tycho.nsa.gov> wrote:
> It looks like commit 415103f9932d45f7927f4b17e3a9a13834cdb9a1 changed
> selinux_inode_init_security()'s handling of SECURITY_FS_USE_MNTPOINT,
> and this change was never propagated to selinux_dentry_init_security().
> However, that commit also did not update
> security/selinux/hooks.c:may_create()'s logic for computing the new file
> label when checking CREATE permission, and therefore introduced a
> potential inconsistency between the label used for the permission check
> and the label assigned to the inode.
>
> That's why I suggested that we need a common helper for all three to
> ensure consistency there.
I think a common helper is harder than it seems. We need the parent dir in
one of the cases the helper has to consider, but finding it is done in three
different ways, depending on the caller:
(1) dentry_init can just use ->d_parent as there's a lock held that prevents
it changing (I think). This could use (2) instead, however.
(2) file_open has to use dget_parent().
(3) inode_init doesn't have any dentries, but rather has the object and
parent inodes.
If we don't mind file_open() always calling dget_parent(), then the common
helper can take the dir inode.
Also, thinking ahead to the possibility of bringing unionmount into the kernel
at some point: union non-dir dentries that are not yet copied up have no inode
attached, but rather fall through to the underlying lower inode in the VFS.
This, however, gives us nowhere to hang the inode label. How expensive is the
security_transition_sid() call?
David
next prev parent reply other threads:[~2015-06-16 16:50 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-05 15:42 [PATCH 0/7] Security: Provide unioned file support David Howells
2014-11-05 15:42 ` [PATCH 1/7] Security: Provide copy-up security hooks for unioned files David Howells
2014-11-06 17:46 ` Casey Schaufler
2014-11-07 14:49 ` David Howells
2014-11-07 14:49 ` David Howells
2014-11-07 21:22 ` Paul Moore
2014-11-07 21:22 ` Paul Moore
2014-11-07 22:10 ` David Howells
2014-11-07 22:10 ` David Howells
2014-11-10 15:28 ` Paul Moore
2014-11-10 15:28 ` Paul Moore
2014-11-05 15:42 ` [PATCH 2/7] Overlayfs: Use copy-up security hooks David Howells
2014-11-07 21:39 ` Paul Moore
2014-11-07 21:39 ` Paul Moore
2014-11-07 22:05 ` David Howells
2014-11-07 22:05 ` David Howells
2014-11-10 15:45 ` Paul Moore
2014-11-10 15:45 ` Paul Moore
2014-11-05 15:42 ` [PATCH 3/7] SELinux: Stub in copy-up handling David Howells
2014-11-07 21:44 ` Paul Moore
2014-11-07 21:44 ` Paul Moore
2014-11-07 22:08 ` David Howells
2014-11-07 22:08 ` David Howells
2014-11-10 15:47 ` Paul Moore
2014-11-10 15:47 ` Paul Moore
2014-11-05 15:42 ` [PATCH 4/7] Security: Pass the union-layer file path into security_file_open() David Howells
2014-11-05 15:43 ` [PATCH 5/7] SELinux: Handle opening of a unioned file David Howells
2014-11-05 16:35 ` Stephen Smalley
2014-11-06 12:03 ` David Howells
2014-11-06 12:03 ` David Howells
2014-11-06 13:13 ` Stephen Smalley
2014-11-06 13:13 ` Stephen Smalley
2014-11-06 13:34 ` David Howells
2014-11-06 13:34 ` David Howells
2014-11-27 14:15 ` David Howells
2014-11-27 14:15 ` David Howells
2014-11-06 12:27 ` David Howells
2014-11-06 12:27 ` David Howells
2014-11-06 12:27 ` David Howells
2014-11-27 17:25 ` David Howells
2014-11-27 17:25 ` David Howells
2015-06-12 15:30 ` David Howells
2015-06-12 15:30 ` David Howells
2015-06-15 12:57 ` Stephen Smalley
2015-06-15 12:57 ` Stephen Smalley
2015-06-16 9:41 ` David Howells
2015-06-16 9:41 ` David Howells
2015-06-16 16:49 ` David Howells [this message]
2015-06-16 16:49 ` David Howells
2015-06-16 17:20 ` Stephen Smalley
2015-06-16 17:20 ` Stephen Smalley
2015-06-16 21:34 ` David Howells
2015-06-16 21:34 ` David Howells
2015-06-17 14:44 ` Stephen Smalley
2015-06-17 14:44 ` Stephen Smalley
2015-06-18 10:15 ` David Howells
2015-06-18 10:15 ` David Howells
2015-06-18 12:48 ` Stephen Smalley
2015-06-18 12:48 ` Stephen Smalley
2015-06-18 15:26 ` David Howells
2015-06-18 15:26 ` David Howells
2015-06-18 10:32 ` David Howells
2015-06-18 10:32 ` David Howells
2015-06-18 12:16 ` Stephen Smalley
2015-06-18 12:16 ` Stephen Smalley
2014-11-05 15:43 ` [PATCH 6/7] SELinux: The copy-up operation must have read permission on the lower file David Howells
2014-11-05 16:43 ` Stephen Smalley
2014-11-05 17:54 ` Stephen Smalley
2014-11-06 13:39 ` Stephen Smalley
2014-11-27 14:17 ` David Howells
2014-11-27 14:17 ` David Howells
2014-11-27 14:21 ` David Howells
2014-11-27 14:21 ` David Howells
2014-11-27 14:21 ` David Howells
2014-11-05 15:43 ` [PATCH 7/7] SELinux: Check against union and lower labels for file ops on lower files David Howells
2014-11-06 17:35 ` [PATCH 0/7] Security: Provide unioned file support Casey Schaufler
2014-11-06 17:35 ` Casey Schaufler
2014-11-06 17:58 ` David Howells
2014-11-06 17:58 ` David Howells
2014-11-06 18:40 ` Casey Schaufler
2014-11-06 18:40 ` Casey Schaufler
2014-11-07 15:21 ` David Howells
2014-11-07 15:21 ` David Howells
2014-11-07 18:54 ` Daniel J Walsh
2014-11-07 18:54 ` Daniel J Walsh
2014-11-09 1:31 ` Casey Schaufler
2014-11-09 1:31 ` Casey Schaufler
2014-11-10 13:59 ` Daniel J Walsh
2014-11-10 13:59 ` Daniel J Walsh
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=7332.1434473388@warthog.procyon.org.uk \
--to=dhowells@redhat.com \
--cc=drquigl@tycho.nsa.gov \
--cc=eparis@parisplace.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=linux-unionfs@vger.kernel.org \
--cc=sds@tycho.nsa.gov \
--cc=selinux@tycho.nsa.gov \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.