linux-kernel - Re: [PATCH] x86: Fix memory leak of init_vdso

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Message-ID: <20110721194329.GA29460@elte.hu>
Date:	Thu, 21 Jul 2011 21:43:30 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Lutomirski <luto@....edu>
Cc:	Andi Kleen <ak@...ux.intel.com>, mingo@...hat.com,
	wzt <wzt.wzt@...il.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, tglx@...utronix.de, hpa@...or.com,
	Michal Hocko <mhocko@...e.cz>,
	Zhitong Wang <zhitong.wangzt@...baba-inc.com>
Subject: Re: [PATCH] x86: Fix memory leak of init_vdso_vars()


* Andrew Lutomirski <luto@....edu> wrote:

> On Thu, Jul 21, 2011 at 2:38 PM, Ingo Molnar <mingo@...e.hu> wrote:
> >
> > * Andrew Lutomirski <luto@....edu> wrote:
> >
> >> On Thu, Jul 21, 2011 at 1:08 PM, Andi Kleen <ak@...ux.intel.com> wrote:
> >> > On Thu, Jul 21, 2011 at 10:33:14AM -0400, Andy Lutomirski wrote:
> >> >> From: Zhitong Wang <wzt.wzt@...il.com>
> >> >>
> >> >> If init_vdso_vars ran out of memory (not very likely), then it would
> >> >> leak a few pages as well.
> >> >>
> >> >> Also rename init_vdso_vars to just init_vdso, since initializing
> >> >> vvars is just about the only thing this function doesn't do.
> >> >
> >> > Just add a GFP_PANIC, there's no way to recover from this.
> >> > Your system will not work without a vdso.
> >>
> >> Ingo objected to this before, although I'm not convinved.  Calling
> >> init_vdso_vars more than once will cause major problems (like
> >> double-patching of alternatives).  If there's too little memory for
> >> it to work, then presumably there's also too little memory to start
> >> init.
> >>
> >>  (Also, I bet that no one ever audited whether the ELF loader works
> >> right if the vDSO failed to load.)
> >>
> >> Ingo?
> >
> > This assumes that the system actually needs an ELF loader - if a
> > static binary is booted via a init= boot parameter it might not be
> > needed.
> 
> I actually meant the kernel's loaded.  But I just looked and it appears correct.
> 
> But I think this whole thing is silly, because I can't see any good
> reason that the vdso needs to allocate memory in the first place.
> I'll send a patch.

that's the perfect solution indeed :)

Thanks,

	Ingo
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