[PATCH 4.19 13/74] fs/adfs: super: fix use-after-free bug

Greg Kroah-Hartman
2019-08-05T13:09:14Z

[ 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@armlinux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 7e099a7a4eb1e..4dc15b2634894 100644
--- a/fs/adfs/super.c
+++ b/fs/adfs/super.c
@@ -369,6 +369,7 @@ 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;
@@ -420,8 +421,10 @@ 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