[PATCH v3 2/3] mm/sparse: fix possible memory leak

[Gavin Shan <shangw@linux.vnet.ibm.com>]

sparse_index_init() is designed to be safe if two copies of it race.  It
uses "index_init_lock" to ensure that, even in the case of a race, only
one CPU will manage to do:

	mem_section[root] = section;

However, in the case where two copies of sparse_index_init() _do_ race,
the one that loses the race will leak the "section" that
sparse_index_alloc() allocated for it.  This patch fixes that leak.

Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
---
 mm/sparse.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/mm/sparse.c b/mm/sparse.c
index 781fa04..a6984d9 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -75,6 +75,20 @@ static struct mem_section noinline __init_refok *sparse_index_alloc(int nid)
 	return section;
 }
 
+static inline void __meminit sparse_index_free(struct mem_section *section)
+{
+	unsigned long size = SECTIONS_PER_ROOT *
+			     sizeof(struct mem_section);
+
+	if (!section)
+		return;
+
+	if (slab_is_available())
+		kfree(section);
+	else
+		free_bootmem(virt_to_phys(section), size);
+}
+
 static int __meminit sparse_index_init(unsigned long section_nr, int nid)
 {
 	static DEFINE_SPINLOCK(index_init_lock);
@@ -102,6 +116,9 @@ static int __meminit sparse_index_init(unsigned long section_nr, int nid)
 	mem_section[root] = section;
 out:
 	spin_unlock(&index_init_lock);
+	if (ret)
+		sparse_index_free(section);
+
 	return ret;
 }
 #else /* !SPARSEMEM_EXTREME */
-- 
1.7.9.5

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