linux-kernel - Re: [PATCH] mm/sl[aou]b: make kfree() aware of error pointers

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Date:	Wed, 10 Sep 2014 16:42:06 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Andrey Ryabinin <ryabinin.a.a@...il.com>
cc:	Theodore Ts'o <tytso@....edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH] mm/sl[aou]b: make kfree() aware of error pointers

On Wed, 10 Sep 2014, Andrey Ryabinin wrote:

> > I of course have no objections to this check being added to whatever
> > static checker, that would be very welcome improvement.
> >
> > Still, I believe that kernel shouldn't be just ignoring kfree(ERR_PTR)
> > happening. Would something like the below be more acceptable?
> >
> >
> >
> > From: Jiri Kosina <jkosina@...e.cz>
> > Subject: [PATCH] mm/sl[aou]b: make kfree() aware of error pointers
> >
> > Freeing if ERR_PTR is not covered by ZERO_OR_NULL_PTR() check already
> > present in kfree(), but it happens in the wild and has disastrous effects.
> >
> > Issue a warning and don't proceed trying to free the memory if
> > CONFIG_DEBUG_SLAB is set.
> >
> 
> This won't work cause CONFIG_DEBUG_SLAB  is only for CONFIG_SLAB=y
> 
> How about just VM_BUG_ON(IS_ERR(ptr)); ?

VM_BUG_ON() makes very little sense to me, as we are going to oops anyway 
later, so it's a lose-lose situation.

VM_WARN_ON() + return seems like much more reasonable choice.

-- 
Jiri Kosina
SUSE Labs
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