From: Igor Stoppa <igor.stoppa@huawei.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Jerome Glisse <jglisse@redhat.com>, Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
<linux-security-module@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Kees Cook <keescook@google.com>
Subject: Re: [RFC] Tagging of vmalloc pages for supporting the pmalloc allocator
Date: Thu, 3 Aug 2017 17:41:24 +0300 [thread overview]
Message-ID: <836b82ae-0d01-af73-d6fd-00343bb2a5b7@huawei.com> (raw)
In-Reply-To: <20170803135549.GW12521@dhcp22.suse.cz>
On 03/08/17 16:55, Michal Hocko wrote:
> On Thu 03-08-17 15:20:31, Igor Stoppa wrote:
>> On 03/08/17 14:48, Michal Hocko wrote:
>>> On Thu 03-08-17 13:11:45, Igor Stoppa wrote:
[...]
>>>> But, to reply more specifically to your advice, yes, I think I could add
>>>> a flag to vm_struct and then retrieve its value, for the address being
>>>> processed, by passing through find_vm_area().
>>>
>>> ... and you can store vm_struct pointer to the struct page there
>>
>> "there" as in the new field of the union?
>> btw, what would be a meaningful name, since "private" is already taken?
>>
>> For simplicity, I'll use, for now, "private2"
>
> why not explicit vm_area?
ok :-)
>>> and you won't need to do the slow find_vm_area. I haven't checked
>> very closely
>>> but this should be possible in principle. I guess other callers might
>>> benefit from this as well.
>>
>> I am confused about this: if "private2" is a pointer, but when I get an
>> address, I do not even know if the address represents a valid pmalloc
>> page, how can i know when it's ok to dereference "private2"?
>
> because you can make all pages which back vmalloc mappings have vm_area
> pointer set.
Ah, now I see, I had missed that the field would be set for *all* pages
backed by vmalloc.
So, given a pointer, I still have to figure out if it refers to a
vmalloc area or not.
However, that is something I need to do anyway, to get the reference to
the corresponding page struct, in case it is indeed a vmalloc address.
--
thanks, igor
next prev parent reply other threads:[~2017-08-03 14:42 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-02 15:14 [RFC] Tagging of vmalloc pages for supporting the pmalloc allocator Igor Stoppa
2017-08-02 17:08 ` Jerome Glisse
2017-08-03 10:11 ` Igor Stoppa
2017-08-03 11:48 ` Michal Hocko
2017-08-03 12:20 ` Igor Stoppa
2017-08-03 13:55 ` Michal Hocko
2017-08-03 14:41 ` Igor Stoppa [this message]
2017-08-03 14:47 ` Jerome Glisse
2017-08-03 15:06 ` Igor Stoppa
2017-08-03 15:15 ` Michal Hocko
2017-08-04 8:02 ` Igor Stoppa
2017-08-04 8:12 ` Michal Hocko
2017-08-07 11:26 ` Igor Stoppa
2017-08-07 11:34 ` Michal Hocko
2017-08-07 13:31 ` Jerome Glisse
2017-08-07 14:13 ` Igor Stoppa
2017-08-07 19:12 ` Jerome Glisse
2017-08-08 12:59 ` Igor Stoppa
2017-08-08 23:15 ` Jerome Glisse
2017-08-09 7:27 ` Igor Stoppa
2017-08-10 7:14 ` Michal Hocko
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