linux-kernel - Re: [RFC] situation with fput() locking (was Re: [PULL REQUEST] : ima-appraisal patches)

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Message-ID: <CA+55aFzaC8YfN_q1TxPbNgpD7AnoAVac2Bqa+ysEji3u7ZQ18A@mail.gmail.com>
Date:	Fri, 20 Apr 2012 14:12:55 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Hugh Dickins <hughd@...gle.com>, linux-fsdevel@...r.kernel.org,
	James Morris <jmorris@...ei.org>,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	David Safford <safford@...ux.vnet.ibm.com>,
	Dmitry Kasatkin <dmitry.kasatkin@...el.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	David Miller <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC] situation with fput() locking (was Re: [PULL REQUEST] :
 ima-appraisal patches)

On Fri, Apr 20, 2012 at 12:58 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>
> So does a bunch of other places.  Let me dig out the call graph circa
> 3.3.0...  Here is the relevant part:

Yes, but a lot of those would actually be helped by a helper function
that does all of:
 - grab mmap_sem
 - call do_m[un]map()
 - release mmap_sem

and that would actually clean them up even in the current case.

And then we could do the cleanup in just the helper function.

Not all, no. But a preparatory patch that just creates the helper
functions for doing brk/mmap/munmap would get rid of a fairly big
chunk of them.

You can visualize how many of them do that by just doing

    git grep -5 do_m[un]*map

and then high-lghting '_write(' (to visually show the
down_write/up_write pairs that surround most of them) by searching for
it.

Are they all like that? No. But most of the ones outside of mm/ do fit
that simple pattern and should probably be fixed up just to have them
not contain VM locking details in them *anyway*.

                    Linus
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