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From: Stephen Smalley <sds@tycho.nsa.gov>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andrew Morton <akpm@osdl.org>, Ingo Molnar <mingo@elte.hu>,
	tglx@linutronix.de, linux-kernel@vger.kernel.org,
	selinux@tycho.nsa.gov, James Morris <jmorris@namei.org>
Subject: Re: [PATCH 2/2] sysctl: Restore the selinux path based label lookup for sysctls.
Date: Thu, 08 Feb 2007 10:01:11 -0500	[thread overview]
Message-ID: <1170946871.11912.250.camel@moss-spartans.epoch.ncsc.mil> (raw)
In-Reply-To: <m17iutmmwh.fsf@ebiederm.dsl.xmission.com>

On Wed, 2007-02-07 at 18:57 -0700, Eric W. Biederman wrote:
> Stephen Smalley <sds@tycho.nsa.gov> writes:
> 
> >
> > One related but separate issue is that the /proc/sys inode labeling is
> > also affected by the sysctl patch series.  Those inodes used to be
> > labeled by selinux_proc_get_sid (from selinux_d_instantiate), but that
> > no longer works, so they now fall back to the superblock SID (generic
> > proc label).  That changes the inode permission checks on an attempt to
> > access a /proc/sys node and will likely cause denials under current
> > policy for confined domains since one wouldn't generally be writing to
> > the generic proc label. If you always called sysctl_perm from the proc
> > sysctl code, we could possibly dispense with inode permission checking
> > on those inodes, e.g. marking them private.
> 
> Like this?
> 
> It seems a little weird but I'm happy with it if you are.
> 
> Eric
> 
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index b9d59c0..7d6f7c7 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -47,6 +47,7 @@ static struct inode *proc_sys_make_inode(struct inode *dir, struct ctl_table *ta
>  	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
>  	inode->i_op = &proc_sys_inode_operations;
>  	inode->i_fop = &proc_sys_file_operations;
> +	inode->i_flags |= S_PRIVATE; /* tell selinux to ignore this inode */
>  	proc_sys_refresh_inode(inode, table);
>  out:
>  	return inode;

Hmmm...turns out to not be quite enough, as the /proc/sys inodes aren't
truly private to the fs, so we can run into them in a variety of
security hooks beyond just the inode hooks, such as
security_file_permission (when reading and writing them via the vfs
helpers), security_sb_mount (when mounting other filesystems on
directories in proc like binfmt_misc), and deeper within the security
module itself (as in flush_unauthorized_files upon inheritance across
execve).  So I think we have to add an IS_PRIVATE() guard within
SELinux, as below.  Note however that the use of the private flag here
could be confusing, as these inodes are _not_ private to the fs, are
exposed to userspace, and security modules must implement the sysctl
hook to get any access control over them.

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 65fb5e8..21bf2f0 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1078,6 +1077,9 @@ static int inode_has_perm(struct task_st
 	struct inode_security_struct *isec;
 	struct avc_audit_data ad;
 
+	if (unlikely (IS_PRIVATE (inode)))
+		return 0;
+
 	tsec = tsk->security;
 	isec = inode->i_security;
 


-- 
Stephen Smalley
National Security Agency


  reply	other threads:[~2007-02-08 15:06 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <200701280106.l0S16CG3019873@shell0.pdx.osdl.net>
     [not found] ` <20070127172410.2b041952.akpm@osdl.org>
     [not found]   ` <1169972718.17469.164.camel@localhost.localdomain>
     [not found]     ` <20070128003549.2ca38dc8.akpm@osdl.org>
     [not found]       ` <20070128093358.GA2071@elte.hu>
     [not found]         ` <20070128095712.GA6485@elte.hu>
     [not found]           ` <20070128100627.GA8416@elte.hu>
     [not found]             ` <20070128104548.a835d859.akpm@osdl.org>
2007-01-28 19:21               ` [PATCH] sysctl selinux: Don't look at table->de Eric W. Biederman
2007-01-29 13:04                 ` Stephen Smalley
2007-01-29 15:23                   ` James Morris
2007-01-29 17:55                     ` Eric W. Biederman
2007-01-29 19:26                       ` Stephen Smalley
2007-01-29 17:43                   ` Eric W. Biederman
2007-01-29 18:43                     ` Stephen Smalley
2007-01-29 19:08                       ` Casey Schaufler
2007-01-29 20:07                         ` Stephen Smalley
2007-01-30 10:25                         ` Christoph Hellwig
2007-01-30 17:19                           ` Casey Schaufler
2007-01-29 19:16                       ` Eric W. Biederman
2007-01-29 23:28                       ` Russell Coker
2007-02-06 21:16                   ` [PATCH 1/2] sysctl: Add a parent entry to ctl_table and set the parent entry Eric W. Biederman
2007-02-06 21:21                     ` [PATCH 2/2] sysctl: Restore the selinux path based label lookup for sysctls Eric W. Biederman
2007-02-07 18:24                       ` Stephen Smalley
2007-02-07 21:12                         ` Stephen Smalley
2007-02-07 21:54                           ` Stephen Smalley
2007-02-07 22:21                             ` Eric W. Biederman
2007-02-08 15:07                               ` Stephen Smalley
2007-02-08  1:57                           ` Eric W. Biederman
2007-02-08 15:01                             ` Stephen Smalley [this message]
2007-02-08 17:53                               ` Eric W. Biederman
2007-02-08 18:13                                 ` Stephen Smalley
2007-02-08 22:17                                   ` Eric W. Biederman
2007-02-08 22:51                                     ` [PATCH 0/5] sysctl cleanup selinux fixes Eric W. Biederman
2007-02-08 22:53                                       ` [PATCH 1/5] sysctl: Remove declaration of nonexistent sysctl_init() Eric W. Biederman
2007-02-08 22:54                                         ` [PATCH 2/5] sysctl: Set the parent field in the root sysctl table Eric W. Biederman
2007-02-08 22:55                                           ` [PATCH 3/5] sysctl: Fix the selinux_sysctl_get_sid Eric W. Biederman
2007-02-08 23:02                                             ` [PATCH 4/5] selinux: Enhance selinux to always ignore private inodes Eric W. Biederman
2007-02-08 23:04                                               ` [PATCH 5/5] sysctl: Hide the sysctl proc inodes from selinux Eric W. Biederman
2007-02-09 12:26                                               ` [PATCH 4/5] selinux: Enhance selinux to always ignore private inodes Stephen Smalley
2007-02-09 12:24                                             ` [PATCH 3/5] sysctl: Fix the selinux_sysctl_get_sid Stephen Smalley
2007-02-09 11:05                                       ` [PATCH 0/5] sysctl cleanup selinux fixes Andrew Morton
2007-02-09 18:09                                         ` Eric W. Biederman

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