linux-kernel - [PATCH 3.18 23/47] ext4: fix possible use after free in ext4_quota

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Date:   Fri, 11 Jan 2019 15:08:08 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jan Kara <jack@...e.cz>,
        Pan Bian <bianpan2016@....com>, Theodore Tso <tytso@....edu>,
        stable@...nel.org
Subject: [PATCH 3.18 23/47] ext4: fix possible use after free in ext4_quota_enable

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

------------------

From: Pan Bian <bianpan2016@....com>

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@...nel.org # 4.6
Reviewed-by: Jan Kara <jack@...e.cz>
Signed-off-by: Pan Bian <bianpan2016@....com>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5389,9 +5389,9 @@ 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;
 }