[PATCH v2 2/3] mm/sparse: fix possible memory leak

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

With CONFIG_SPARSEMEM_EXTREME, the root memory section descriptors
are allocated by slab or bootmem allocator. Also, the descriptors
might have been allocated and initialized during the hotplug path.
However, the memory chunk allocated in current implementation wouldn't
be put into the available pool if that has been allocated. The situation
will lead to memory leak.

Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
---
 mm/sparse.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/mm/sparse.c b/mm/sparse.c
index 781fa04..a803599 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -75,6 +75,22 @@ static struct mem_section noinline __init_refok *sparse_index_alloc(int nid)
 	return section;
 }
 
+static void noinline __init_refok sparse_index_free(struct mem_section *section,
+						    int nid)
+{
+	unsigned long size = SECTIONS_PER_ROOT *
+			     sizeof(struct mem_section);
+
+	if (!section)
+		return;
+
+	if (slab_is_available())
+		kfree(section);
+	else
+		free_bootmem_node(NODE_DATA(nid),
+			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 +118,9 @@ 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, nid);
+
 	return ret;
 }
 #else /* !SPARSEMEM_EXTREME */
-- 
1.7.9.5

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