linux-kernel - Re: [PATCH 1/3] uprobes: fix the usage of install_special

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Message-ID: <20150709220225.GB15485@redhat.com>
Date:	Fri, 10 Jul 2015 00:02:25 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] uprobes: fix the usage of install_special_mapping()

On 07/09, Andy Lutomirski wrote:
>
> On Thu, Jul 9, 2015 at 2:44 PM, Oleg Nesterov <oleg@...hat.com> wrote:
> > install_special_mapping(pages) expects that "pages" is the zero-
> > terminated array while xol_add_vma() passes &area->page, this means
> > that special_mapping_fault() can wrongly use the next member in
> > xol_area (vaddr) as "struct page *".
> >
> > Fortunately, this area is not expandable so pgoff != 0 isn't possible
> > (modulo bugs in special_mapping_vmops), but still this does not look
> > good.
> >
>
> I fell for that awhile back, too, causing a bizarre HPET bug.

I guess you mean no_pages[] = {NULL} in map_vdso() ?

uprobes differs, I think pgoff != 0 is not actually possible (assuming
we fix special_mapping_fault). But this doesn't matter, this is wrong
anyway.

> What zeroes pages[1]?

Heh ;) Thanks. I'll send v2.

Oleg.

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