[RFC 0/3] Slight improvements for OOM/Futex

From: Nico Pache <npache@redhat.com>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: "Michael Ellerman" <mpe@ellerman.id.au>,
	"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
	"Paul Mackerras" <paulus@samba.org>,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Nicholas Piggin" <npiggin@gmail.com>,
	"Logan Gunthorpe" <logang@deltatee.com>,
	"Hari Bathini" <hbathini@linux.ibm.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	"Yang Shi" <shy828301@gmail.com>,
	"Miaohe Lin" <linmiaohe@huawei.com>,
	"William Kucharski" <william.kucharski@oracle.com>,
	"Hugh Dickins" <hughd@google.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Darren Hart" <dvhart@infradead.org>,
	"Davidlohr Bueso" <dave@stgolabs.net>,
	"André Almeida" <andrealmeid@collabora.com>,
	"Arjan van de Ven" <arjan@infradead.org>,
	"Ulrich Drepper" <drepper@redhat.com>,
	"Michal Hocko" <mhocko@suse.com>
Subject: [RFC 0/3] Slight improvements for OOM/Futex
Date: Thu, 21 Apr 2022 15:05:30 -0400	[thread overview]
Message-ID: <20220421190533.1601879-1-npache@redhat.com> (raw)

The following 3 patches were developed while working on the OOM/Futex
fix. 

Patch 1: This is a nonfunctional change. The vma_is_anonymous function
originally led to some confusion about what the oom reaper is checking
for in __oom_reap_task_mm. This patch makes that function name more 
verbose.

Patch 2: Futex cleanup was designed with silent failures. Printing this
failure would have led to more quickly finding the issue. This
introduces a pr_info if the exit path has any issues walking the
userspace list.

Patch 3: During the debug process I noticed that the oom_reap_task_mm
function was always running twice for the same mm_struct; Once in the
exit path and once in the oom_reaper. By checking the MMF_OOM_SKIP we
can prevent these unnecissary double calls. I'd like some input from
David Rientjes here with regards to CVE-2018-1000200, I want to make
sure we are not reintroducing that CVE.

Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "André Almeida" <andrealmeid@collabora.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Ulrich Drepper <drepper@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Nico Pache <npache@redhat.com>

Nico Pache (3):
  mm: change vma_is_anonymous to vma_is_private_anon
  futex: exit: Print a warning when futex_cleanup fails
  exit: Check for MMF_OOM_SKIP in exit_mmap

 arch/powerpc/mm/book3s64/pgtable.c |  2 +-
 fs/userfaultfd.c                   |  2 +-
 include/linux/huge_mm.h            |  2 +-
 include/linux/mm.h                 |  2 +-
 kernel/futex/core.c                | 44 ++++++++++++++++++------------
 mm/gup.c                           |  4 +--
 mm/huge_memory.c                   | 10 +++----
 mm/madvise.c                       |  4 +--
 mm/memory.c                        | 10 +++----
 mm/migrate_device.c                |  6 ++--
 mm/mincore.c                       |  2 +-
 mm/mmap.c                          |  7 +++--
 mm/oom_kill.c                      |  2 +-
 mm/userfaultfd.c                   |  8 +++---
 14 files changed, 57 insertions(+), 48 deletions(-)

-- 
2.35.1