From: Mike Kravetz <mike.kravetz@oracle.com>
To: Rik van Riel <riel@redhat.com>, Michal Hocko <mhocko@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
fweimer@redhat.com, colm@allcosts.net, akpm@linux-foundation.org,
keescook@chromium.org, luto@amacapital.net, wad@chromium.org,
mingo@kernel.org, kirill@shutemov.name, dave.hansen@intel.com
Subject: Re: [PATCH 2/2] mm,fork: introduce MADV_WIPEONFORK
Date: Fri, 11 Aug 2017 10:07:04 -0700 [thread overview]
Message-ID: <a9d00a69-bc53-acab-6e63-f4b263f88cbb@oracle.com> (raw)
In-Reply-To: <1502470781.6577.49.camel@redhat.com>
On 08/11/2017 09:59 AM, Rik van Riel wrote:
> On Fri, 2017-08-11 at 09:36 -0700, Mike Kravetz wrote:
>> On 08/11/2017 08:23 AM, Rik van Riel wrote:
>>> On Thu, 2017-08-10 at 17:23 +0200, Michal Hocko wrote:
>>>> On Sun 06-08-17 10:04:25, Rik van Riel wrote:
>>>> [...]
>>>>> diff --git a/kernel/fork.c b/kernel/fork.c
>>>>> index 17921b0390b4..db1fb2802ecc 100644
>>>>> --- a/kernel/fork.c
>>>>> +++ b/kernel/fork.c
>>>>> @@ -659,6 +659,13 @@ static __latent_entropy int
>>>>> dup_mmap(struct
>>>>> mm_struct *mm,
>>>>> tmp->vm_flags &= ~(VM_LOCKED |
>>>>> VM_LOCKONFAULT);
>>>>> tmp->vm_next = tmp->vm_prev = NULL;
>>>>> file = tmp->vm_file;
>>>>> +
>>>>> + /* With VM_WIPEONFORK, the child gets an empty
>>>>> VMA. */
>>>>> + if (tmp->vm_flags & VM_WIPEONFORK) {
>>>>> + tmp->vm_file = file = NULL;
>>>>> + tmp->vm_ops = NULL;
>>>>> + }
>>>>
>>>> What about VM_SHARED/|VM)MAYSHARE flags. Is it OK to keep the
>>>> around?
>>>> At
>>>> least do_anonymous_page SIGBUS on !vm_ops && VM_SHARED. Or do I
>>>> miss
>>>> where those flags are cleared?
>>>
>>> Huh, good spotting. That makes me wonder why the test case that
>>> Mike and I ran worked just fine on a MAP_SHARED|MAP_ANONYMOUS VMA,
>>> and returned zero-filled memory when read by the child process.
>>
>> Well, I think I still got a BUG with a MAP_SHARED|MAP_ANONYMOUS vma
>> on
>> your v2 patch. Did not really want to start a discussion on the
>> implementation until the issue of exactly what VM_WIPEONFORK was
>> supposed
>> to do was settled.
>
> It worked here, but now I don't understand why :)
>
>>>
>>> OK, I'll do a minimal implementation for now, which will return
>>> -EINVAL if MADV_WIPEONFORK is called on a VMA with MAP_SHARED
>>> and/or an mmapped file.
>>>
>>> It will work the way it is supposed to with anonymous MAP_PRIVATE
>>> memory, which is likely the only memory it will be used on, anyway.
>>>
>>
>> Seems reasonable.
>>
>> You should also add VM_HUGETLB to those returning -EINVAL. IIRC, a
>> VM_HUGETLB vma even without VM_SHARED expects vm_file != NULL.
>
> In other words (flags & MAP_SHARED || vma->vm_file) would catch
> hugetlbfs, too?
Yes, that should catch hugetlbfs.
--
Mike Kravetz
next prev parent reply other threads:[~2017-08-11 17:07 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-06 14:04 [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK riel
2017-08-06 14:04 ` [PATCH 1/2] x86,mpx: make mpx depend on x86-64 to free up VMA flag riel
2017-08-06 14:04 ` [PATCH 2/2] mm,fork: introduce MADV_WIPEONFORK riel
2017-08-10 15:23 ` Michal Hocko
2017-08-11 15:23 ` Rik van Riel
2017-08-11 16:36 ` Mike Kravetz
2017-08-11 16:59 ` Rik van Riel
2017-08-11 17:07 ` Mike Kravetz [this message]
2017-08-07 13:22 ` [PATCH v2 0/2] mm,fork,security: " Michal Hocko
2017-08-07 13:46 ` Michal Hocko
2017-08-07 14:19 ` Florian Weimer
2017-08-10 13:06 ` Michal Hocko
2017-08-07 14:59 ` Rik van Riel
2017-08-09 9:59 ` Kirill A. Shutemov
2017-08-09 12:31 ` Rik van Riel
2017-08-09 12:42 ` Florian Weimer
2017-08-10 13:05 ` Michal Hocko
2017-08-10 13:23 ` Colm MacCárthaigh
2017-08-10 15:36 ` Michal Hocko
[not found] ` <CAAF6GDeno6RpHf1KORVSxUL7M-CQfbWFFdyKK8LAWd_6PcJ55Q@mail.gmail.com>
2017-08-10 17:01 ` Michal Hocko
2017-08-10 22:09 ` Colm MacCárthaigh
2017-08-11 14:06 ` Michal Hocko
2017-08-11 14:11 ` Florian Weimer
2017-08-11 14:24 ` Michal Hocko
2017-08-11 15:24 ` Florian Weimer
2017-08-11 15:31 ` Michal Hocko
[not found] ` <CAAF6GDcNoDUaDSxV6N12A_bOzo8phRUX5b8-OBteuN0AmeCv0g@mail.gmail.com>
2017-08-07 16:02 ` Colm MacCárthaigh
2017-08-10 13:21 ` Michal Hocko
2017-08-10 14:11 ` Michal Hocko
2017-08-07 18:23 ` Mike Kravetz
2017-08-08 9:58 ` Florian Weimer
2017-08-08 13:15 ` Rik van Riel
2017-08-08 15:19 ` Mike Kravetz
2017-08-08 15:22 ` Florian Weimer
2017-08-08 15:46 ` Rik van Riel
2017-08-08 16:48 ` Colm MacCárthaigh
2017-08-08 16:52 ` Matthew Wilcox
2017-08-08 18:45 ` Rik van Riel
2017-08-10 15:31 ` Michal Hocko
-- strict thread matches above, loose matches on Subject: below --
2017-08-11 21:28 [PATCH v4 " riel
2017-08-11 21:28 ` [PATCH 2/2] mm,fork: " riel
2017-08-15 22:51 ` Andrew Morton
2017-08-16 2:18 ` Rik van Riel
2017-08-17 22:50 ` Andrew Morton
2017-08-18 16:28 ` Rik van Riel
2017-08-18 18:15 ` Andrew Morton
2017-08-19 0:02 ` Rik van Riel
2017-08-18 17:25 ` Mike Kravetz
2017-08-11 19:19 [PATCH v3 0/2] mm,fork,security: " riel
2017-08-11 19:19 ` [PATCH 2/2] mm,fork: " riel
2017-08-11 19:42 ` Linus Torvalds
2017-08-11 20:27 ` Rik van Riel
2017-08-11 20:50 ` Linus Torvalds
2017-08-04 19:07 [PATCH 0/2] mm,fork,security: " riel
2017-08-04 19:07 ` [PATCH 2/2] mm,fork: " riel
2017-08-04 23:09 ` Mike Kravetz
2017-08-05 14:05 ` Rik van Riel
2017-08-14 15:45 ` kbuild test robot
2017-08-04 19:01 [PATCH 0/2] mm,fork: MADV_WIPEONFORK - an empty VMA in the child riel
2017-08-04 19:01 ` [PATCH 2/2] mm,fork: introduce MADV_WIPEONFORK riel
2017-08-05 18:46 ` kbuild test robot
2017-08-05 19:33 ` kbuild test robot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=a9d00a69-bc53-acab-6e63-f4b263f88cbb@oracle.com \
--to=mike.kravetz@oracle.com \
--cc=akpm@linux-foundation.org \
--cc=colm@allcosts.net \
--cc=dave.hansen@intel.com \
--cc=fweimer@redhat.com \
--cc=keescook@chromium.org \
--cc=kirill@shutemov.name \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@amacapital.net \
--cc=mhocko@kernel.org \
--cc=mingo@kernel.org \
--cc=riel@redhat.com \
--cc=wad@chromium.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).