linux-kernel - [PATCH 4.14 082/183] blk-mq-debugfs: dont allow write on attributes with seq

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 25 Apr 2018 12:35:02 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ming Lei <ming.lei@...hat.com>,
        Eryu Guan <eguan@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.14 082/183] blk-mq-debugfs: dont allow write on attributes with seq_operations set

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

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

From: Eryu Guan <eguan@...hat.com>


[ Upstream commit 6b136a24b05c81a24e0b648a4bd938bcd0c4f69e ]

Attributes that only implement .seq_ops are read-only, any write to
them should be rejected. But currently kernel would crash when
writing to such debugfs entries, e.g.

chmod +w /sys/kernel/debug/block/<dev>/requeue_list
echo 0 > /sys/kernel/debug/block/<dev>/requeue_list
chmod -w /sys/kernel/debug/block/<dev>/requeue_list

Fix it by returning -EPERM in blk_mq_debugfs_write() when writing to
such attributes.

Cc: Ming Lei <ming.lei@...hat.com>
Signed-off-by: Eryu Guan <eguan@...hat.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 block/blk-mq-debugfs.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -704,7 +704,11 @@ static ssize_t blk_mq_debugfs_write(stru
 	const struct blk_mq_debugfs_attr *attr = m->private;
 	void *data = d_inode(file->f_path.dentry->d_parent)->i_private;
 
-	if (!attr->write)
+	/*
+	 * Attributes that only implement .seq_ops are read-only and 'attr' is
+	 * the same with 'data' in this case.
+	 */
+	if (attr == data || !attr->write)
 		return -EPERM;
 
 	return attr->write(data, buf, count, ppos);