[PATCH 4.20 073/145] ext4: fix possible use after free in ext4_quota_enable

From: Greg Kroah-Hartman
Date: Mon Jan 07 2019 - 07:38:45 EST

4.20-stable review patch. If anyone has any objections, please let me know.


From: Pan Bian <bianpan2016@xxxxxxx>

commit 61157b24e60fb3cd1f85f2c76a7b1d628f970144 upstream.

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@xxxxxxxxxx # 4.6
Reviewed-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Pan Bian <bianpan2016@xxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

fs/ext4/super.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5713,9 +5713,9 @@ static int ext4_quota_enable(struct supe
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;