linux-kernel - Re: [Patch BUGFIX] kcore: fix its wrong size on x86

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <2375c9f90906160829g3d605836yb4c5b9beeac50c5f@mail.gmail.com>
Date:	Tue, 16 Jun 2009 23:29:18 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Tao Ma <tao.ma@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Alexey Dobriyan <adobriyan@...il.com>
Subject: Re: [Patch BUGFIX] kcore: fix its wrong size on x86_64

On Mon, Jun 15, 2009 at 6:08 PM, Eric W. Biederman<ebiederm@...ssion.com> wrote:
> Amerigo Wang <xiyou.wangcong@...il.com> writes:
>
>> Fix wrong /proc/kcore size on x86_64.
>>
>> x86_64 uses __va() macro to caculate the virtual address passed to kclist_add()
>> but decodes it with its own macro kc_vadd_to_offset(). This is wrong.
>
> Ok.  I finally understand what is going on here, and no kc_vaddr_to_offset
> is not wrong when applied to a virtual address.  In fact I expect the current
> definition makes things a bit more predictable.
>
> And yes kclist_add is must be given a virtual address
>
>> Also, according to Documentation/x86/x86_64/mm.txt, kc_vaddr_to_offset()
>> is wrong too.
>
> How so?  The file offset is a number space that is different from both
> physical and virtual addresses.

Why? They _do_ have some calculated relations.

>
>> So just remove them, use the generic macro.
>
> I think a case can be made either way.  In practice neither answer
> gives us a dense offset space on x86_64 so I think I prefer the
> current definition which sets or clears the high bits as opposed
> to something that mangles the address more.
>

I am trying to dig more... There must be something wrong there.

>
> It uses get_kcore_size and (size_t)high_memory - PAGE_OFFSET + PAGE_SIZE;
> The second definition being bogus as it has nothing to do with which
> offsets are accepted.

Agreed. Maybe we can just remove the second one and update the doc?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/