linux-kernel - [PATCH] mm: Fix mem_cgroup_oom

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Date:   Tue,  5 Sep 2017 17:30:39 +0200
From:   Laurent Dufour <ldufour@...ux.vnet.ibm.com>
To:     linux-mm@...ck.org, akpm@...ux-foundation.org,
        kirill@...temov.name, linux-kernel@...r.kernel.org
Subject: [PATCH] mm: Fix mem_cgroup_oom_disable() call missing

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.

Fixes: bae473a423f6 ("mm: introduce fault_env")
Signed-off-by: Laurent Dufour <ldufour@...ux.vnet.ibm.com>
---
 mm/memory.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 56e48e4593cb..274547075486 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3888,6 +3888,11 @@ int handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
 	/* 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.
@@ -3895,11 +3900,6 @@ int handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
 	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
-- 
2.7.4