[PATCH 4.9 09/42] fs/adfs: super: fix use-after-free bug

[Greg Kroah-Hartman]

[ Upstream commit 5808b14a1f52554de612fee85ef517199855e310 ]

Fix a use-after-free bug during filesystem initialisation, where we
access the disc record (which is stored in a buffer) after we have
released the buffer.

Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/adfs/super.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/adfs/super.c b/fs/adfs/super.c
index c9fdfb1129335..e42c300015090 100644
--- a/fs/adfs/super.c
+++ b/fs/adfs/super.c
@@ -368,6 +368,7 @@ static int adfs_fill_super(struct super_block *sb, void *data, int silent)
 	struct buffer_head *bh;
 	struct object_info root_obj;
 	unsigned char *b_data;
+	unsigned int blocksize;
 	struct adfs_sb_info *asb;
 	struct inode *root;
 	int ret = -EINVAL;
@@ -419,8 +420,10 @@ static int adfs_fill_super(struct super_block *sb, void *data, int silent)
 		goto error_free_bh;
 	}
 
+	blocksize = 1 << dr->log2secsize;
 	brelse(bh);
-	if (sb_set_blocksize(sb, 1 << dr->log2secsize)) {
+
+	if (sb_set_blocksize(sb, blocksize)) {
 		bh = sb_bread(sb, ADFS_DISCRECORD / sb->s_blocksize);
 		if (!bh) {
 			adfs_error(sb, "couldn't read superblock on "
-- 
2.20.1