linux-kernel - [PATCH 4.9 07/14] mm/memory.c: fix mem_cgroup_oom

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Message-Id: <20170912165254.101785546@linuxfoundation.org>
Date:   Tue, 12 Sep 2017 09:58:21 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Laurent Dufour <ldufour@...ux.vnet.ibm.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.9 07/14] mm/memory.c: fix mem_cgroup_oom_disable() call missing

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Laurent Dufour <ldufour@...ux.vnet.ibm.com>

commit de0c799bba2610a8e1e9a50d76a28614520a4cd4 upstream.

Seen while reading the code, in handle_mm_fault(), in the case
arch_vma_access_permitted() is failing the call to
mem_cgroup_oom_disable() is not made.

To fix that, move the call to mem_cgroup_oom_enable() after calling
arch_vma_access_permitted() as it should not have entered the memcg OOM.

Link: http://lkml.kernel.org/r/1504625439-31313-1-git-send-email-ldufour@linux.vnet.ibm.com
Fixes: bae473a423f6 ("mm: introduce fault_env")
Signed-off-by: Laurent Dufour <ldufour@...ux.vnet.ibm.com>
Acked-by: Kirill A. Shutemov <kirill@...temov.name>
Acked-by: Michal Hocko <mhocko@...e.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 mm/memory.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3596,6 +3596,11 @@ int handle_mm_fault(struct vm_area_struc
 	/* do counter updates before entering really critical section. */
 	check_sync_rss_stat(current);

+	if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE,
+					    flags & FAULT_FLAG_INSTRUCTION,
+					    flags & FAULT_FLAG_REMOTE))
+		return VM_FAULT_SIGSEGV;
+
 	/*
 	 * Enable the memcg OOM handling for faults triggered in user
 	 * space.  Kernel faults are handled more gracefully.
@@ -3603,11 +3608,6 @@ int handle_mm_fault(struct vm_area_struc
 	if (flags & FAULT_FLAG_USER)
 		mem_cgroup_oom_enable();

-	if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE,
-					    flags & FAULT_FLAG_INSTRUCTION,
-					    flags & FAULT_FLAG_REMOTE))
-		return VM_FAULT_SIGSEGV;
-
 	if (unlikely(is_vm_hugetlb_page(vma)))
 		ret = hugetlb_fault(vma->vm_mm, vma, address, flags);
 	else