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Date:   Mon, 18 May 2020 10:20:52 +0900
From:   js1304@...il.com
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        kernel-team@....com, Vlastimil Babka <vbabka@...e.cz>,
        Christoph Hellwig <hch@...radead.org>,
        Roman Gushchin <guro@...com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Michal Hocko <mhocko@...e.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: [PATCH 06/11] mm/hugetlb: do not modify user provided gfp_mask

From: Joonsoo Kim <iamjoonsoo.kim@....com>

It's not good practice to modify user input. Instead of using it to
build correct gfp_mask for APIs, this patch introduces another gfp_mask
field, __gfp_mask, for internal usage.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
---
 mm/hugetlb.c  | 15 ++++++++-------
 mm/internal.h |  2 ++
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 53edd02..5f43b7e 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1069,15 +1069,15 @@ static struct page *dequeue_huge_page_nodemask(struct hstate *h,
 	struct zoneref *z;
 	int node = NUMA_NO_NODE;
 
-	zonelist = node_zonelist(ac->nid, ac->gfp_mask);
+	zonelist = node_zonelist(ac->nid, ac->__gfp_mask);
 
 retry_cpuset:
 	cpuset_mems_cookie = read_mems_allowed_begin();
 	for_each_zone_zonelist_nodemask(zone, z, zonelist,
-			gfp_zone(ac->gfp_mask), ac->nmask) {
+			gfp_zone(ac->__gfp_mask), ac->nmask) {
 		struct page *page;
 
-		if (!cpuset_zone_allowed(zone, ac->gfp_mask))
+		if (!cpuset_zone_allowed(zone, ac->__gfp_mask))
 			continue;
 		/*
 		 * no need to ask again on the same node. Pool is node rather than
@@ -1952,7 +1952,7 @@ static struct page *alloc_migrate_huge_page(struct hstate *h,
 	if (hstate_is_gigantic(h))
 		return NULL;
 
-	page = alloc_fresh_huge_page(h, ac->gfp_mask,
+	page = alloc_fresh_huge_page(h, ac->__gfp_mask,
 				ac->nid, ac->nmask, NULL);
 	if (!page)
 		return NULL;
@@ -1990,9 +1990,10 @@ struct page *alloc_buddy_huge_page_with_mpol(struct hstate *h,
 struct page *alloc_huge_page_nodemask(struct hstate *h,
 				struct alloc_control *ac)
 {
-	ac->gfp_mask |= htlb_alloc_mask(h);
+	ac->__gfp_mask = htlb_alloc_mask(h);
+	ac->__gfp_mask |= ac->gfp_mask;
 	if (ac->thisnode && ac->nid != NUMA_NO_NODE)
-		ac->gfp_mask |= __GFP_THISNODE;
+		ac->__gfp_mask |= __GFP_THISNODE;
 
 	spin_lock(&hugetlb_lock);
 	if (h->free_huge_pages - h->resv_huge_pages > 0) {
@@ -2011,7 +2012,7 @@ struct page *alloc_huge_page_nodemask(struct hstate *h,
 	 * will not come from CMA area
 	 */
 	if (ac->skip_cma)
-		ac->gfp_mask &= ~__GFP_MOVABLE;
+		ac->__gfp_mask &= ~__GFP_MOVABLE;
 
 	return alloc_migrate_huge_page(h, ac);
 }
diff --git a/mm/internal.h b/mm/internal.h
index 6b6507e..3239d71 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -620,6 +620,8 @@ struct alloc_control {
 	gfp_t gfp_mask;
 	bool thisnode;
 	bool skip_cma;
+
+	gfp_t __gfp_mask;	/* Used internally in API implementation */
 };
 
 #endif	/* __MM_INTERNAL_H */
-- 
2.7.4

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