linux-kernel - Re: [v3][PATCH 5/5] Merge code for single andmultiple-instancemounts

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Date:	Mon, 11 May 2009 19:09:01 -0400
From:	Eric Paris <eparis@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	marc.c.dionne@...il.com, eparis@...isplace.org, hch@....de,
	alan@...rguk.ukuu.org.uk, serue@...ibm.com, hpa@...or.com,
	sukadev@...ibm.com, linux-kernel@...r.kernel.org, jbacik@...hat.com
Subject: Re: [v3][PATCH 5/5] Merge code for single
 andmultiple-instancemounts

On Mon, 2009-05-11 at 15:40 -0700, Andrew Morton wrote:
> On Mon, 11 May 2009 15:15:02 -0700
> Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com> wrote:
> 
> > Marc Dionne [marc.c.dionne@...il.com] wrote:
> > > On 05/07/2009 07:21 PM, Sukadev Bhattiprolu wrote:
> > >> Er. I meant add following lines after the memset().
> > >>
> > >> |         opts->mode    = DEVPTS_DEFAULT_MODE;
> > >> |         opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
> > >
> > > Adding those two lines (with . instead of ->) does fix the issue for me, 
> > > thanks.
> > >
> > > | > Of course we would still need to understand if/
> > > | > why this patch changes the settings.
> > >
> > > That particular patch changed things because the original memcpy in 
> > > new_pts_mount() did this:
> > >
> > > memcpy(&fsi->mount_opts, opts, sizeof(opts));
> > >
> > > where opts was a pointer, not a structure.  So only the first few bytes of 
> > > the blank opts actually got copied over.  The patch moved this memcpy to 
> > > devpts_get_sb() and in the process fixed the sizeof error.
> > 
> > Here is a cleaner fix - When user space (/etc/rc.sysinit on RHEL5) mounts
> > devpts, this problem might be masked since the mount system call could pass
> > a non-NULL 'data' parmeter to devpts_get_sb().
> > 
> > I tested this patch by directly calling the system call mount() with a NULL
> > data parameter. If you/Eric/Peter can confirm that this works for you, I will
> > send this patch to Andrew.
> 
> You already sent it ;)
> 
> > >From 2f7746f4df78ff57125c4714f0cd64e739ccf804 Mon Sep 17 00:00:00 2001
> > From: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
> > Date: Mon, 11 May 2009 13:11:11 -0700
> > Subject: [PATCH] devpts: Correctly set default options
> > 
> > devpts_get_sb() calls memset(0) to clear mount options and calls
> > parse_mount_options() if user specified any mount options. The memset(0) is
> > bogus since the 'mode' and 'ptmxmode' options are non-zero by default.
> > parse_mount_options() restores options to default anyway and can properly deal
> > with NULL mount options.
> > 
> > So in devpts_get_sb() remove memset(0) and call parse_mount_options() even for
> > NULL mount options.
> > 
> > Bug reported by Eric Paris: http://lkml.org/lkml/2009/5/7/448.
> 
> This patch fixes a post-2.6.29 regression, yes?

I believe so, yes.

> > Signed-off-by: Sukadev Bhattiprolu (sukadev@...ibm.com)
> 
> Please use angled brackets around the email address.  Some lame
> person's scripts probably require it.  <whistles innocently>
> 
> Under the he-merged-it-last rule, this patch should formally go via
> Al's VFS tree.  But I would happily accept a stfu-and-merge it?

You have another tested, reviewed, and ack'd on this patch from me.  I
personally would say send it away!

-Eric

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