From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:52104 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753768AbeDYKkV (ORCPT ); Wed, 25 Apr 2018 06:40:21 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ming Lei , Eryu Guan , Jens Axboe , Sasha Levin Subject: [PATCH 4.14 082/183] blk-mq-debugfs: dont allow write on attributes with seq_operations set Date: Wed, 25 Apr 2018 12:35:02 +0200 Message-Id: <20180425103245.800521498@linuxfoundation.org> In-Reply-To: <20180425103242.532713678@linuxfoundation.org> References: <20180425103242.532713678@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eryu Guan [ 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//requeue_list echo 0 > /sys/kernel/debug/block//requeue_list chmod -w /sys/kernel/debug/block//requeue_list Fix it by returning -EPERM in blk_mq_debugfs_write() when writing to such attributes. Cc: Ming Lei Signed-off-by: Eryu Guan Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- 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);