Date: Thu, 1 Apr 2004 16:29:43 -0800
From: Andrew Morton <akpm@osdl.org>
To: Sridhar Samudrala <sri@us.ibm.com>
Cc: hch@infradead.org, linux-kernel@vger.kernel.org
Subject: Re: CONFIG_DEBUG_PAGEALLOC and virt_addr_valid()
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Sridhar Samudrala <sri@us.ibm.com> wrote:
>
> On Thu, 1 Apr 2004, Christoph Hellwig wrote:
> 
> > On Thu, Apr 01, 2004 at 11:11:39AM -0800, Sridhar Samudrala wrote:
> > > When CONFIG_DEBUG_PAGEALLOC is enabled, i am noticing that virt_addr_valid()
> > > (called from sctp_is_valid_kaddr()) is returning true even for freed objects.
> > > Is this a bug or expected behavior?
> >
> > Generally every use of virt_addr_valid() is a bug.  What are you trying to
> > do?
> 
> We are trying to validate a kernel address that is passed by the user. Is
> there a better way to do that?

yup.  Pass the user an integer.

> When an SCTP association is established, the pointer to the association
> structure is passed to the user as an identifier of the association. This
> identifier is used in the later calls by the user.

Please don't do that.  See lib/idr.c.  I expect it does exactly what you
want.
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