From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Hugh Dickins <hughd@google.com>,
David Rientjes <rientjes@google.com>,
Vlastimil Babka <vbabka@suse.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Dave Hansen <dave.hansen@intel.com>, Mel Gorman <mgorman@suse.de>,
Rik van Riel <riel@redhat.com>, Christoph Lameter <cl@gentwo.org>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Steve Capper <steve.capper@linaro.org>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.cz>,
Jerome Marchand <jmarchan@redhat.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: page-flags behavior on compound pages: a worry
Date: Wed, 12 Aug 2015 17:35:09 +0300 [thread overview]
Message-ID: <20150812143509.GA12320@node.dhcp.inet.fi> (raw)
In-Reply-To: <alpine.LSU.2.11.1508061121120.7500@eggly.anvils>
On Thu, Aug 06, 2015 at 12:24:22PM -0700, Hugh Dickins wrote:
> > IIUC, the only potentially problematic callsites left are physical memory
> > scanners. This code requires audit. I'll do that.
>
> Please.
I haven't finished the exercise yet. But here's an issue I believe present
in current *Linus* tree:
WARNING: multiple messages have this Message-ID (diff)
From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Hugh Dickins <hughd@google.com>,
David Rientjes <rientjes@google.com>,
Vlastimil Babka <vbabka@suse.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Dave Hansen <dave.hansen@intel.com>, Mel Gorman <mgorman@suse.de>,
Rik van Riel <riel@redhat.com>, Christoph Lameter <cl@gentwo.org>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Steve Capper <steve.capper@linaro.org>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.cz>,
Jerome Marchand <jmarchan@redhat.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: page-flags behavior on compound pages: a worry
Date: Wed, 12 Aug 2015 17:35:09 +0300 [thread overview]
Message-ID: <20150812143509.GA12320@node.dhcp.inet.fi> (raw)
In-Reply-To: <alpine.LSU.2.11.1508061121120.7500@eggly.anvils>
On Thu, Aug 06, 2015 at 12:24:22PM -0700, Hugh Dickins wrote:
> > IIUC, the only potentially problematic callsites left are physical memory
> > scanners. This code requires audit. I'll do that.
>
> Please.
I haven't finished the exercise yet. But here's an issue I believe present
in current *Linus* tree:
>From e78eec7d7a8c4cba8b5952a997973f7741e704f4 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Date: Wed, 12 Aug 2015 17:09:16 +0300
Subject: [PATCH] mm: fix potential race in isolate_migratepages_block()
Hugh has pointed that compound_head() call can be unsafe in some context.
There's one example:
CPU0 CPU1
isolate_migratepages_block()
page_count()
compound_head()
!!PageTail() == true
put_page()
tail->first_page = NULL
head = tail->first_page
alloc_pages(__GFP_COMP)
prep_compound_page()
tail->first_page = head
__SetPageTail(p);
!!PageTail() == true
<head == NULL dereferencing>
The race is pure theoretical. I don't it's possible to trigger it in
practice. But who knows.
This can be fixed by avoiding compound_head() in unsafe context.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
---
mm/compaction.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 86f04e556f96..bec727b700d3 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -787,7 +787,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
* admittedly racy check.
*/
if (!page_mapping(page) &&
- page_count(page) > page_mapcount(page))
+ atomic_read(&page->_count) > page_mapcount(page))
continue;
/* If we already hold the lock, we can skip some rechecking */
--
Kirill A. Shutemov
next prev parent reply other threads:[~2015-08-12 14:35 UTC|newest]
Thread overview: 117+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-19 17:08 [PATCH 00/16] Sanitize usage of ->flags and ->mapping for tail pages Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-19 17:08 ` [PATCH 01/16] mm: consolidate all page-flags helpers in <linux/page-flags.h> Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-23 0:10 ` Hugh Dickins
2015-03-23 0:10 ` Hugh Dickins
2015-03-19 17:08 ` [PATCH 02/16] page-flags: trivial cleanup for PageTrans* helpers Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-23 0:12 ` Hugh Dickins
2015-03-23 0:12 ` Hugh Dickins
2015-03-19 17:08 ` [PATCH 03/16] page-flags: introduce page flags policies wrt compound pages Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-20 20:35 ` Andrew Morton
2015-03-20 20:35 ` Andrew Morton
2015-03-20 21:34 ` Kirill A. Shutemov
2015-03-20 21:34 ` Kirill A. Shutemov
2015-03-19 17:08 ` [PATCH 04/16] page-flags: define PG_locked behavior on " Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-27 15:11 ` Mateusz Krawczuk
2015-03-27 15:11 ` Mateusz Krawczuk
2015-03-27 15:13 ` Mateusz Krawczuk
2015-03-27 15:13 ` Mateusz Krawczuk
2015-03-27 15:13 ` Mateusz Krawczuk
2015-03-27 16:37 ` Kirill A. Shutemov
2015-03-27 16:37 ` Kirill A. Shutemov
2015-03-27 16:37 ` Kirill A. Shutemov
2015-07-15 20:20 ` Christoph Lameter
2015-07-15 20:20 ` Christoph Lameter
2015-08-06 4:15 ` page-flags behavior on compound pages: a worry Hugh Dickins
2015-08-06 4:15 ` Hugh Dickins
2015-08-06 15:33 ` Kirill A. Shutemov
2015-08-06 15:33 ` Kirill A. Shutemov
2015-08-06 19:24 ` Hugh Dickins
2015-08-06 19:24 ` Hugh Dickins
2015-08-06 20:45 ` Christoph Lameter
2015-08-06 20:45 ` Christoph Lameter
2015-08-07 14:50 ` Kirill A. Shutemov
2015-08-07 14:50 ` Kirill A. Shutemov
2015-08-07 15:28 ` Christoph Lameter
2015-08-07 15:28 ` Christoph Lameter
2015-08-10 11:09 ` Kirill A. Shutemov
2015-08-10 11:09 ` Kirill A. Shutemov
2015-08-10 13:50 ` Christoph Lameter
2015-08-10 13:50 ` Christoph Lameter
2015-08-07 14:49 ` Kirill A. Shutemov
2015-08-07 14:49 ` Kirill A. Shutemov
2015-08-13 5:10 ` Hugh Dickins
2015-08-13 5:10 ` Hugh Dickins
2015-08-12 14:35 ` Kirill A. Shutemov [this message]
2015-08-12 14:35 ` Kirill A. Shutemov
2015-08-12 14:47 ` Vlastimil Babka
2015-08-12 14:47 ` Vlastimil Babka
2015-08-12 21:16 ` Andrew Morton
2015-08-12 21:16 ` Andrew Morton
2015-08-12 22:21 ` Kirill A. Shutemov
2015-08-12 22:21 ` Kirill A. Shutemov
2015-08-13 4:12 ` Hugh Dickins
2015-08-13 4:12 ` Hugh Dickins
2015-03-19 17:08 ` [PATCH 05/16] page-flags: define behavior of FS/IO-related flags on compound pages Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-19 18:29 ` Dave Hansen
2015-03-19 18:29 ` Dave Hansen
2015-03-19 20:02 ` Kirill A. Shutemov
2015-03-19 20:02 ` Kirill A. Shutemov
2015-03-23 0:02 ` Hugh Dickins
2015-03-23 0:02 ` Hugh Dickins
2015-03-23 12:17 ` Kirill A. Shutemov
2015-03-23 12:17 ` Kirill A. Shutemov
2015-03-24 22:54 ` Hugh Dickins
2015-03-24 22:54 ` Hugh Dickins
2015-03-25 10:23 ` Kirill A. Shutemov
2015-03-25 10:23 ` Kirill A. Shutemov
2015-03-25 18:56 ` Hugh Dickins
2015-03-25 18:56 ` Hugh Dickins
2015-03-19 17:08 ` [PATCH 06/16] page-flags: define behavior of LRU-related " Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-19 17:08 ` [PATCH 07/16] page-flags: define behavior SL*B-related " Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-19 17:08 ` [PATCH 08/16] page-flags: define behavior of Xen-related " Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-19 17:08 ` [PATCH 09/16] page-flags: define PG_reserved behavior " Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2020-01-31 15:24 ` Chris Wilson
2020-02-03 15:18 ` Kirill A. Shutemov
2020-02-03 15:24 ` Chris Wilson
2020-02-03 17:10 ` David Hildenbrand
2020-02-03 17:29 ` Christoph Hellwig
2015-03-19 17:08 ` [PATCH 10/16] page-flags: define PG_swapbacked " Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-19 17:08 ` [PATCH 11/16] page-flags: define PG_swapcache " Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-19 17:08 ` [PATCH 12/16] page-flags: define PG_mlocked " Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-19 17:08 ` [PATCH 13/16] page-flags: define PG_uncached " Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-19 17:08 ` [PATCH 14/16] page-flags: define PG_uptodate " Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-19 17:08 ` [PATCH 15/16] page-flags: look on head page if the flag is encoded in page->mapping Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-19 17:08 ` [PATCH 16/16] mm: sanitize page->mapping for tail pages Kirill A. Shutemov
2015-03-19 17:08 ` Kirill A. Shutemov
2015-03-23 0:28 ` [PATCH 00/16] Sanitize usage of ->flags and ->mapping " Hugh Dickins
2015-03-23 0:28 ` Hugh Dickins
2015-03-23 10:04 ` Kirill A. Shutemov
2015-03-23 10:04 ` Kirill A. Shutemov
2015-03-24 23:42 ` Hugh Dickins
2015-03-24 23:42 ` Hugh Dickins
2015-03-25 10:55 ` Kirill A. Shutemov
2015-03-25 10:55 ` Kirill A. Shutemov
2015-03-24 17:39 ` Konstantin Khlebnikov
2015-03-24 17:39 ` Konstantin Khlebnikov
2015-03-24 20:04 ` Kirill A. Shutemov
2015-03-24 20:04 ` Kirill A. Shutemov
2015-07-15 20:20 ` Christoph Lameter
2015-07-15 20:20 ` Christoph Lameter
2015-07-15 21:18 ` Kirill A. Shutemov
2015-07-15 21:18 ` Kirill A. Shutemov
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