linux-kernel - Re: [PATCH] exec: Make do_coredump more robust and safer when using pipes in core

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Date:	Sun, 28 Jun 2009 23:00:54 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Neil Horman <nhorman@...driver.com>,
	linux-kernel@...r.kernel.org, earl_chew@...lent.com,
	Oleg Nesterov <oleg@...hat.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH] exec: Make do_coredump more robust and safer when using pipes in core_pattern

On Sun, Jun 28, 2009 at 01:52:35PM -0700, Andrew Morton wrote:
> On Sun, 28 Jun 2009 21:31:12 +0200 Andi Kleen <andi@...stfloor.org> wrote:
> 
> > > One way would be to add a new sysctl-externs.h and then put all the
> > > declarations in there.  That file gets included by sysctl.c and by each
> > > file which shares a global with sysctl.c
> > 
> > Long ago I had a experimental patch to put sysctls into a new ELF section. The 
> > you could simply put a DEFINE_SYSCTL(....) into the appropiate source file
> > which defined the variable and most of the tables went.
> > 
> > No externs, no mess, no patch collisions, everything much nicer.
> > 
> > The only problem was that it didn't support the numerical sysctl
> > space, so that would need to be removed first.
> > 
> > It's deprecated for quite some time now:
> > 
> >   if (msg_count < 5) {
> >                 msg_count++;
> >                 printk(KERN_INFO
> >                         "warning: process `%s' used the deprecated sysctl "
> >                         "system call with ", current->comm);
> > 
> > Should it finally go now? If yes I could polish up the old patch again.
> > 
> 
> I suspect that it will be a long time before we can actually remove the
> numerical sysctl support, if ever.  In _theory_ we should support it

To my knowledge the only one that is really commonly used is the one
used by glibc, but that can be kept of course.

> for ever.  But in practice, we could probably remove it with a minimum
> of disruption a few years hence, but it's hard to work this out.

One alternative would be to just keep a translation table
numerical -> symbolic for now and remove that later. That would
still not need any externs at least.

Or perhaps make a explicit CONFIG_SYSCTL_NUMERICAL and ask
users to report in.

> 
> When was the last time we saw a "warning: process `%s' used the
> obsolete bdflush system call" warning?  A quick google here says 2004. 
> Is that data?  A bit, I guess.

bdflush? 

> Maybe Eric has thought about this issue?

feature-removal says Sep 2010 (which seems a bit long in the future)

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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