linux-kernel - Re: [PATCH 2/3] flex_arrays: allow zero length flex arrays

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Date:	Tue, 26 Apr 2011 16:44:31 -0400
From:	Eric Paris <eparis@...hat.com>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
Cc:	steffen.klassert@...unet.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, selinux@...ho.nsa.gov,
	sds@...ho.nsa.gov
Subject: Re: [PATCH 2/3] flex_arrays: allow zero length flex arrays

On Tue, 2011-04-26 at 13:38 -0700, Dave Hansen wrote:
> On Mon, 2011-04-25 at 21:45 -0400, Eric Paris wrote:
> > Just like kmalloc will allow one to allocate a 0 length segment of memory
> > flex arrays should do the same thing.  It should bomb if you try to use
> > something, but it should at least allow the allocation.
> > 
> > Based-on-patch-by: Steffen Klassert <steffen.klassert@...unet.com>
> > Signed-off-by: Eric Paris <eparis@...hat.com>
> > ---
> > 
> >  lib/flex_array.c |   11 ++++++++++-
> >  1 files changed, 10 insertions(+), 1 deletions(-)
> > 
> > diff --git a/lib/flex_array.c b/lib/flex_array.c
> > index 0c33b24..2554a5f 100644
> > --- a/lib/flex_array.c
> > +++ b/lib/flex_array.c
> > @@ -253,9 +253,16 @@ int flex_array_prealloc(struct flex_array *fa, unsigned int start,
> >  	unsigned int end;
> >  	struct flex_array_part *part;
> > 
> > +	if (!fa->total_nr_elements && !start)
> > +		return 0;
> 
> I guess it works either way, but I'd say that checking for a zero 'len'
> prealloc would be more important (and meaningful) than checking a zero
> 'start'.
> 
> If someone passed start=0 and len=44 for a fa->total_nr_elements=0
> array, I'd expect -ENOSPC, but this would return 0.

will fix.

if (!nr_elements && !start)
	return 0;

-Eric

> 
> -- Dave
> 


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