ext4: fix possible use after free in ext4_quota_enable

The function frees qf_inode via iput but then pass qf_inode to
lockdep_set_quota_inode on the failure path. This may result in a
use-after-free bug. The patch frees df_inode only when it is never used.

Fixes: daf647d2dd5 ("ext4: add lockdep annotations for i_data_sem")
Cc: stable@kernel.org # 4.6
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 3616244604317ffdb5c4801d4ec42a24499a9da7..d22e761aaa1853767376bd1b86cd4c32ca3d00b5 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5713,9 +5713,9 @@ static int ext4_quota_enable(struct super_block *sb, int type, int format_id,
        qf_inode->i_flags |= S_NOQUOTA;
        lockdep_set_quota_inode(qf_inode, I_DATA_SEM_QUOTA);
        err = dquot_enable(qf_inode, type, format_id, flags);
-       iput(qf_inode);
        if (err)
                lockdep_set_quota_inode(qf_inode, I_DATA_SEM_NORMAL);
+       iput(qf_inode);
 
        return err;
 }