linux-kernel - [PATCH v4 01/13] mm: fix type width of section to/from pfn conversion macros

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Date:   Wed, 15 Mar 2017 23:06:53 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     akpm@...ux-foundation.org
Cc:     Michal Hocko <mhocko@...e.com>, linux-nvdimm@...ts.01.org,
        Logan Gunthorpe <logang@...tatee.com>,
        linux-kernel@...r.kernel.org,
        Stephen Bates <stephen.bates@...rosemi.com>,
        linux-mm@...ck.org, Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH v4 01/13] mm: fix type width of section to/from pfn
 conversion macros

section_nr_to_pfn() will silently accept an argument that is too small
to contain a pfn. Cast the argument to an unsigned long, similar to
PFN_PHYS(). Fix up pfn_to_section_nr() in the same way.

This was discovered in __add_pages() when converting it to use an
signed integer for the loop variable.

Cc: Michal Hocko <mhocko@...e.com>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Logan Gunthorpe <logang@...tatee.com>
Cc: Mel Gorman <mgorman@...hsingularity.net>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Stephen Bates <stephen.bates@...rosemi.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 include/linux/mmzone.h |    4 ++--
 mm/memory_hotplug.c    |    4 +---
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 8e02b3750fe0..ffa9503d5be5 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1064,8 +1064,8 @@ static inline unsigned long early_pfn_to_nid(unsigned long pfn)
 #error Allocator MAX_ORDER exceeds SECTION_SIZE
 #endif
 
-#define pfn_to_section_nr(pfn) ((pfn) >> PFN_SECTION_SHIFT)
-#define section_nr_to_pfn(sec) ((sec) << PFN_SECTION_SHIFT)
+#define pfn_to_section_nr(pfn) ((unsigned long)(pfn) >> PFN_SECTION_SHIFT)
+#define section_nr_to_pfn(sec) ((unsigned long)(sec) << PFN_SECTION_SHIFT)
 
 #define SECTION_ALIGN_UP(pfn)	(((pfn) + PAGES_PER_SECTION - 1) & PAGE_SECTION_MASK)
 #define SECTION_ALIGN_DOWN(pfn)	((pfn) & PAGE_SECTION_MASK)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 6fa7208bcd56..e1751ca002fa 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -536,9 +536,7 @@ static int __meminit __add_section(int nid, struct zone *zone,
 int __ref __add_pages(int nid, struct zone *zone, unsigned long phys_start_pfn,
 			unsigned long nr_pages)
 {
-	unsigned long i;
-	int err = 0;
-	int start_sec, end_sec;
+	int err = 0, i, start_sec, end_sec;
 	struct vmem_altmap *altmap;
 
 	clear_zone_contiguous(zone);