fs: dlm: add debugfs rawmsg send functionality

This patch adds a dlm functionality to send a raw dlm message to a
specific cluster node. This raw message can be build by user space and
send out by writing the message to "rawmsg" dlm debugfs file.

There is a in progress scapy dlm module which provides a easy build of
DLM messages in user space. For example:

DLM(h_cmd=3, o_nextcmd=1, h_nodeid=1, h_lockspace=0xe4f48a18, ...)

The goal is to provide an easy reproducable state to crash DLM or to
fuzz the DLM kernel stack if there are possible ways to crash it.

Note: that if the sequence number is zero and dlm version is not set to
3.1 the kernel will automatic will set a right sequence number, otherwise
DLM stack testing is not possible.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/fs/dlm/debug_fs.c b/fs/dlm/debug_fs.c
index 47e9d57e4cae..555904eeea8e 100644
--- a/fs/dlm/debug_fs.c
+++ b/fs/dlm/debug_fs.c
@@ -768,6 +768,42 @@ static int dlm_version_show(struct seq_file *file, void *offset)
 }
 DEFINE_SHOW_ATTRIBUTE(dlm_version);
 
+static ssize_t dlm_rawmsg_write(struct file *fp, const char __user *user_buf,
+				size_t count, loff_t *ppos)
+{
+	void *buf;
+	int ret;
+
+	if (count > PAGE_SIZE || count < sizeof(struct dlm_header))
+		return -EINVAL;
+
+	buf = kmalloc(PAGE_SIZE, GFP_NOFS);
+	if (!buf)
+		return -ENOMEM;
+
+	if (copy_from_user(buf, user_buf, count)) {
+		ret = -EFAULT;
+		goto out;
+	}
+
+	ret = dlm_midcomms_rawmsg_send(fp->private_data, buf, count);
+	if (ret)
+		goto out;
+
+	kfree(buf);
+	return count;
+
+out:
+	kfree(buf);
+	return ret;
+}
+
+static const struct file_operations dlm_rawmsg_fops = {
+	.open	= simple_open,
+	.write	= dlm_rawmsg_write,
+	.llseek	= no_llseek,
+};
+
 void *dlm_create_debug_comms_file(int nodeid, void *data)
 {
 	struct dentry *d_node;
@@ -782,6 +818,7 @@ void *dlm_create_debug_comms_file(int nodeid, void *data)
 	debugfs_create_file("send_queue_count", 0444, d_node, data,
 			    &dlm_send_queue_cnt_fops);
 	debugfs_create_file("version", 0444, d_node, data, &dlm_version_fops);
+	debugfs_create_file("rawmsg", 0200, d_node, data, &dlm_rawmsg_fops);
 
 	return d_node;
 }