linux-kernel - [PATCH AUTOSEL 4.14 30/35] hugetlbfs: fix memory leak for resv

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Message-Id: <20190424144709.30215-30-sashal@kernel.org>
Date:   Wed, 24 Apr 2019 10:47:04 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>, linux-mm@...ck.org
Subject: [PATCH AUTOSEL 4.14 30/35] hugetlbfs: fix memory leak for resv_map

From: Mike Kravetz <mike.kravetz@...cle.com>

[ Upstream commit 58b6e5e8f1addd44583d61b0a03c0f5519527e35 ]

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
inode->i_mapping to bd_inode->i_mapping.  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.

Link: http://lkml.kernel.org/r/20190401213101.16476-1-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>
Reported-by: Yufen Yu <yuyufen@...wei.com>
Suggested-by: Yufen Yu <yuyufen@...wei.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 eb6f3de29f69..dd28a9b287da 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -730,11 +730,17 @@ 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) {
@@ -766,8 +772,10 @@ 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;
 }
-- 
2.19.1