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

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Date:	Thu, 08 Feb 2007 15:17:24 -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, James Morris <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:

> Possibly, during setup upon initial policy load (initiated by /sbin/init
> these days) from selinux_complete_init, as early userspace may have
> already been accessing them.

I believe if we chose we could walk the dentry tree under the root inode
and find all of these.

>>   If all of the accesses
>> that we care about go through inode_doinit_with_dentry we can just
>> walk the dcache to get the names, and that should work for the normal
>> proc case as well.
>
> Walking the proc_dir_entry tree (or the ctl_table tree) is preferable as
> it is a stable, user-immutable representation.  Also avoids taking the
> dcache lock.

The dcache lock is valid.  Since the per filesystem dentry tree is just
a mirror of the filesystem data there is no advantage over using
the proc_dir_entry or ctl_table tree.  (If you start messing with mounts
that is another matter.

>> If it doesn't look easy to solve this another way I will certainly
>> go with marking the inodes private.

I hereby conclude this doesn't look easy enough to solve another way,
to get it solved in a timely manner.  Since the cost is only 2 lines
of code to use private inodes if we want to fix this later it should
not be difficult.

Eric
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