From mboxrd@z Thu Jan  1 00:00:00 1970
From: ebiederm@xmission.com (Eric W. Biederman)
Subject: Re: [PATCH, RESEND] procfs: silence lockdep warning about read vs. exec seq_file
Date: Mon, 04 Aug 2014 20:42:11 -0700
Message-ID: <87d2cfzjos.fsf@x220.int.ebiederm.org>
References: <1407010227-2269-1-git-send-email-kirill@shutemov.name>
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Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	David Howells <dhowells@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Sasha Levin <levinsasha928@gmail.com>,
	Cyrill Gorcunov <gorcunov@openvz.org>,
	Oleg Nesterov <oleg@redhat.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <1407010227-2269-1-git-send-email-kirill@shutemov.name> (Kirill
	A. Shutemov's message of "Sat, 2 Aug 2014 23:10:27 +0300")
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org

"Kirill A. Shutemov" <kirill@shutemov.name> writes:

> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
>
> Testcase:
>
>   cat /proc/self/maps >/dev/null
>   chmod +x /proc/self/net/packet
>   exec /proc/self/net/packet
>
> It triggers lockdep warning:

> I don't know why we allow "chmod +x" on some proc files, notably net-related.
> Is it a bug?

It looks like we simply did not remove the ability to make those files
executable when we realized executable proc files could be a problem.

I expect that part of proc could use an audit where someone figures out
what makes sense.  It does appear that chmod XXX /proc/generic_file
is explicitly supported.  So we would have to be delicate with any
changes in that area to avoid creating userspace regressions.

Eric