linux-kernel - Re: [PATCH 2/2] sysctl: Restore the selinux path based label lookup for sysctls.

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Date:	Wed, 07 Feb 2007 18:57:34 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Stephen Smalley <sds@...ho.nsa.gov>
Cc:	Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...e.hu>,
	tglx@...utronix.de, linux-kernel@...r.kernel.org,
	selinux@...ho.nsa.gov, jmorris@...ei.org
Subject: Re: [PATCH 2/2] sysctl: Restore the selinux path based label lookup for sysctls.

Stephen Smalley <sds@...ho.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;
-
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