[PATCH v2] hugetlbfs: fix memory leak for resv_map

[Yufen Yu <yuyufen@huawei.com>]

When .mknod create a block device file in hugetlbfs, it will
allocate an inode, and kmalloc a 'struct resv_map' in resv_map_alloc().
For now, inode->i_mapping->private_data is used to point the resv_map.
However, when open the device, bd_acquire() will set i_mapping as
bd_inode->imapping, result in resv_map memory leak.

We fix it by waiting until a call to hugetlb_reserve_pages() to allocate
the inode specific resv_map. We could then remove the resv_map allocation
at inode creation time.

Programs to reproduce:
	mount -t hugetlbfs nodev hugetlbfs
	mknod hugetlbfs/dev b 0 0
	exec 30<> hugetlbfs/dev
	umount hugetlbfs/

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
 fs/hugetlbfs/inode.c | 10 ++--------
 mm/hugetlb.c         |  6 ++++++
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index a7fa037b876b..eb87cfb80eb9 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -741,11 +741,6 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb,
 					umode_t mode, dev_t dev)
 {
 	struct inode *inode;
-	struct resv_map *resv_map;
-
-	resv_map = resv_map_alloc();
-	if (!resv_map)
-		return NULL;
 
 	inode = new_inode(sb);
 	if (inode) {
@@ -757,7 +752,7 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb,
 				&hugetlbfs_i_mmap_rwsem_key);
 		inode->i_mapping->a_ops = &hugetlbfs_aops;
 		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
-		inode->i_mapping->private_data = resv_map;
+		inode->i_mapping->private_data = NULL;
 		info->seals = F_SEAL_SEAL;
 		switch (mode & S_IFMT) {
 		default:
@@ -780,8 +775,7 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb,
 			break;
 		}
 		lockdep_annotate_inode_mutex_key(inode);
-	} else
-		kref_put(&resv_map->refs, resv_map_release);
+	}
 
 	return inode;
 }
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 8dfdffc34a99..088fd1239d49 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4462,6 +4462,12 @@ int hugetlb_reserve_pages(struct inode *inode,
 	 */
 	if (!vma || vma->vm_flags & VM_MAYSHARE) {
 		resv_map = inode_resv_map(inode);
+		if (!resv_map) {
+			resv_map = resv_map_alloc();
+			if (!resv_map)
+				return -ENOMEM;
+			inode->i_mapping->private_data = resv_map;
+		}
 
 		chg = region_chg(resv_map, from, to);
 
-- 
2.16.2.dirty