From: Vlastimil Babka <vbabka@suse.cz>
To: Ajay Kaher <akaher@vmware.com>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
Cc: "torvalds@linux-foundation.org" <torvalds@linux-foundation.org>,
"punit.agrawal@arm.com" <punit.agrawal@arm.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"kirill.shutemov@linux.intel.com"
<kirill.shutemov@linux.intel.com>,
"willy@infradead.org" <willy@infradead.org>,
"will.deacon@arm.com" <will.deacon@arm.com>,
"mszeredi@redhat.com" <mszeredi@redhat.com>,
"stable@vger.kernel.org" <stable@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Srivatsa Bhat <srivatsab@vmware.com>,
"srivatsa@csail.mit.edu" <srivatsa@csail.mit.edu>,
Alexey Makhalov <amakhalov@vmware.com>,
Srinidhi Rao <srinidhir@vmware.com>,
Vikash Bansal <bvikas@vmware.com>,
Anish Swaminathan <anishs@vmware.com>,
Vasavi Sirnapalli <vsirnapalli@vmware.com>,
Steven Rostedt <srostedt@vmware.com>,
"stable@kernel.org" <stable@kernel.org>,
Ben Hutchings <ben@decadent.org.uk>
Subject: Re: [PATCH v2 6/8] mm: prevent get_user_pages() from overflowing page refcount
Date: Wed, 6 Nov 2019 09:55:30 +0100 [thread overview]
Message-ID: <35d74931-2c18-00ff-7622-522a79be9103@suse.cz> (raw)
In-Reply-To: <0E5175FB-7058-4211-9AA4-9D5E2F6A30B9@vmware.com>
On 10/25/19 8:18 AM, Ajay Kaher wrote:
> On 17/10/19, 9:58 PM, "Ajay Kaher" <akaher@vmware.com> wrote:
>
>> > This seems to have the same issue as the 4.9 stable version [1], in not
>> > touching the arch-specific gup.c variants.
>> >
>> > [1]
>> > https://lore.kernel.org/lkml/6650323f-dbc9-f069-000b-f6b0f941a065@suse.cz/
>>
>> Thanks Vlastimil for highlighting this here.
>>
>> Yes, arch-specific gup.c variants also need to handle not only for 4.4.y,
>> however it should be handled till 4.19.y. I believe it's better to start
>> from 4.19.y and then backport those changes till 4.4.y.
>>
>> Affected areas of gup.c (where page->count have been used) are:
>> #1: get_page() used in these files and this is safe as
>> it's defined in mm.h (here it's already taken care of)
>> #2: get_head_page_multiple() has following:
>> VM_BUG_ON_PAGE(page_count(page) == 0, page);
>> Need to change this to:
>> VM_BUG_ON_PAGE(page_ref_zero_or_close_to_overflow(page), page);
>> #3: Some of the files have used page_cache_get_speculative(),
>> page_cache_add_speculative() with combination of compound_head(),
>> this scenario needs to be handled as it was handled here:
>> https://lore.kernel.org/stable/1570581863-12090-7-git-send-email-akaher@vmware.com/
>>
>> Please share with me any suggestions or patches if you have already
>> worked on this.
>>
>> Could we handle arch-specific gup.c in different patch sets and
>> let these patches to merge to 4.4.y?
>
> Vlastimil, please suggest if it's fine to merge these patches to 4.4.y
I'm not sure if it makes much sense to merge them without the arch-specific gup
support, when we're aware that it's missing.
> and handle arch-specific gup.c in different patch sets starts from 4.19.y,
Actually arch-specific gup.c were removed in 4.13, so it's enough to start from
4.9.y, which I'm going to finally look into.
> then backport all the way to 4.4.y.
>
> Greg, any suggestion from your side.
>
>> - Ajay
>
>
>
>
next prev parent reply other threads:[~2019-11-06 8:55 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-09 0:44 [PATCH v2 0/8] Backported fixes for 4.4 stable tree Ajay Kaher
2019-10-09 0:44 ` [PATCH v2 1/8] mm: make page ref count overflow check tighter and more explicit Ajay Kaher
2019-10-09 0:44 ` [PATCH v2 2/8] mm: add 'try_get_page()' helper function Ajay Kaher
2019-10-09 0:44 ` [PATCH v2 3/8] mm: handle PTE-mapped tail pages in gerneric fast gup implementaiton Ajay Kaher
2019-10-09 0:44 ` [PATCH v2 4/8] mm, gup: remove broken VM_BUG_ON_PAGE compound check for hugepages Ajay Kaher
2019-10-09 0:44 ` [PATCH v2 5/8] mm, gup: ensure real head page is ref-counted when using hugepages Ajay Kaher
2019-10-09 0:44 ` [PATCH v2 6/8] mm: prevent get_user_pages() from overflowing page refcount Ajay Kaher
2019-10-09 13:13 ` Vlastimil Babka
2019-10-17 16:28 ` Ajay Kaher
2019-10-25 6:18 ` Ajay Kaher
2019-11-06 8:55 ` Vlastimil Babka [this message]
2019-11-11 5:00 ` Ajay Kaher
2019-11-21 20:38 ` gregkh
2019-11-29 9:08 ` Vlastimil Babka
2019-10-09 0:44 ` [PATCH v2 7/8] pipe: add pipe_buf_get() helper Ajay Kaher
2019-10-09 0:44 ` [PATCH v2 8/8] fs: prevent page refcount overflow in pipe_buf_get Ajay Kaher
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=35d74931-2c18-00ff-7622-522a79be9103@suse.cz \
--to=vbabka@suse.cz \
--cc=akaher@vmware.com \
--cc=akpm@linux-foundation.org \
--cc=amakhalov@vmware.com \
--cc=anishs@vmware.com \
--cc=ben@decadent.org.uk \
--cc=bvikas@vmware.com \
--cc=gregkh@linuxfoundation.org \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mszeredi@redhat.com \
--cc=punit.agrawal@arm.com \
--cc=srinidhir@vmware.com \
--cc=srivatsa@csail.mit.edu \
--cc=srivatsab@vmware.com \
--cc=srostedt@vmware.com \
--cc=stable@kernel.org \
--cc=stable@vger.kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=vsirnapalli@vmware.com \
--cc=will.deacon@arm.com \
--cc=willy@infradead.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).