linux-kernel - Re: [PATCH] scatterlist: Validate page before calling PageSlab()

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Message-ID: <20191007061324.GB17978@infradead.org>
Date:   Sun, 6 Oct 2019 23:13:24 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Alan Mikhak <alan.mikhak@...ive.com>
Cc:     linux-kernel@...r.kernel.org, martin.petersen@...cle.com,
        alexios.zavras@...el.com, ming.lei@...hat.com,
        gregkh@...uxfoundation.org, tglx@...utronix.de, jgg@...pe.ca,
        christophe.leroy@....fr, palmer@...ive.com,
        paul.walmsley@...ive.com
Subject: Re: [PATCH] scatterlist: Validate page before calling PageSlab()

On Mon, Sep 30, 2019 at 04:22:35PM -0700, Alan Mikhak wrote:
> From: Alan Mikhak <alan.mikhak@...ive.com>
> 
> Modify sg_miter_stop() to validate the page pointer
> before calling PageSlab(). This check prevents a crash
> that will occur if PageSlab() gets called with a page
> pointer that is not backed by page struct.
> 
> A virtual address obtained from ioremap() for a physical
> address in PCI address space can be assigned to a
> scatterlist segment using the public scatterlist API
> as in the following example:

As Jason pointed out that is not a valid use of scatterlist.  What
are you trying to do here at a higher level?