kernel-hardening - Re: [PATCH] slab: Redefine ZERO_SIZE_PTR to include ERR

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Message-ID: <CAOfkYf765S3sef+gdN7h34iSCzxXxU6ifTb9572WksCqNXo0WA@mail.gmail.com>
Date: Sun, 20 Oct 2019 11:36:42 +0530
From: Shyam Saini <mayhs11saini@...il.com>
To: Matthew Wilcox <willy@...radead.org>, Christopher Lameter <cl@...ux.com>
Cc: linux-mm <linux-mm@...ck.org>, 
	Kernel Hardening <kernel-hardening@...ts.openwall.com>, Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] slab: Redefine ZERO_SIZE_PTR to include ERR_PTR range

Hi Matthew, Christopher,

> > > This will help error related to ERR_PTR stand out better.
> >
> > Maybe make ZERO_SIZE_PTR an ERRNO value instead? Then allow ERR_PTRs to be
> > used instead of ZERO_SIZE_PTRs
> >
> > ERRNO_ZERO_OBJECT
> >
> > or something like that?
>
> I was wondering about something like that too, but allocating zero bytes
> isn't actually an error, and if we have code that does something like:
>
>         void *p = my_funky_alloc(size, ...);
>
>         if (IS_ERR(p))
>                 return PTR_ERR(p);
>
> then we might get this errno returned to userspace.
>
> The change is definitely worth thinking about.

Any further comments on this ?

Please let me know.

Thanks!!

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