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Subject[PATCH] hugetlbfs: fix memory leak for resv_map
Date
When mknod is used to create a block special file in hugetlbfs, it will
allocate an inode and kmalloc a 'struct resv_map' via resv_map_alloc().
inode->i_mapping->private_data will point the newly allocated resv_map.
However, when the device special file is opened bd_acquire() will
set i_mapping as bd_inode->imapping. Thus the pointer to the allocated
resv_map is lost and the structure is leaked.

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

resv_map structures are only needed for inodes which can have associated
page allocations. To fix the leak, only allocate resv_map for those
inodes which could possibly be associated with page allocations.

Reported-by: Yufen Yu <yuyufen@huawei.com>
Suggested-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
fs/hugetlbfs/inode.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 6189ba80b57b..f76e44d1aa54 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -752,11 +752,17 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb,
umode_t mode, dev_t dev)
{
struct inode *inode;
- struct resv_map *resv_map;
+ struct resv_map *resv_map = NULL;

- resv_map = resv_map_alloc();
- if (!resv_map)
- return NULL;
+ /*
+ * Reserve maps are only needed for inodes that can have associated
+ * page allocations.
+ */
+ if (S_ISREG(mode) || S_ISLNK(mode)) {
+ resv_map = resv_map_alloc();
+ if (!resv_map)
+ return NULL;
+ }

inode = new_inode(sb);
if (inode) {
@@ -791,8 +797,10 @@ 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);
+ } else {
+ if (resv_map)
+ kref_put(&resv_map->refs, resv_map_release);
+ }

return inode;
}
--
2.20.1
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