[PATCH 4.17 097/324] batman-adv: Fix debugfs path for renamed hardif

Greg Kroah-Hartman
2018-08-23T08:49:29Z

From: Sven Eckelmann <sven@narfation.org>

[ Upstream commit 36dc621ceca1be3ec885aeade5fdafbbcc452a6d ]

batman-adv is creating special debugfs directories in the init
net_namespace for each valid hard-interface (net_device). But it is
possible to rename a net_device to a completely different name then the
original one.

It can therefore happen that a user registers a new net_device which gets
the name "wlan0" assigned by default. batman-adv is also adding a new
directory under $debugfs/batman-adv/ with the name "wlan0".

The user then decides to rename this device to "wl_pri" and registers a
different device. The kernel may now decide to use the name "wlan0" again
for this new device. batman-adv will detect it as a valid net_device and
tries to create a directory with the name "wlan0" under
$debugfs/batman-adv/. But there already exists one with this name under
this path and thus this fails. batman-adv will detect a problem and
rollback the registering of this device.

batman-adv must therefore take care of renaming the debugfs directories
for hard-interfaces whenever it detects such a net_device rename.

Fixes: 5bc7c1eb44f2 ("batman-adv: add debugfs structure for information per interface")
Reported-by: John Soros <sorosj@gmail.com>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/batman-adv/debugfs.c | 20 ++++++++++++++++++++
net/batman-adv/debugfs.h | 6 ++++++
net/batman-adv/hard-interface.c | 3 +++
3 files changed, 29 insertions(+)

--- a/net/batman-adv/debugfs.c
+++ b/net/batman-adv/debugfs.c
@@ -19,6 +19,7 @@
#include "debugfs.h"
#include "main.h"

+#include <linux/dcache.h>
#include <linux/debugfs.h>
#include <linux/err.h>
#include <linux/errno.h>
@@ -344,6 +345,25 @@ out:
}

/**
+ * batadv_debugfs_rename_hardif() - Fix debugfs path for renamed hardif
+ * @hard_iface: hard interface which was renamed
+ */
+void batadv_debugfs_rename_hardif(struct batadv_hard_iface *hard_iface)
+{
+ const char *name = hard_iface->net_dev->name;
+ struct dentry *dir;
+ struct dentry *d;
+
+ dir = hard_iface->debug_dir;
+ if (!dir)
+ return;
+
+ d = debugfs_rename(dir->d_parent, dir, dir->d_parent, name);
+ if (!d)
+ pr_err("Can't rename debugfs dir to %s\n", name);
+}
+
+/**
* batadv_debugfs_del_hardif() - delete the base directory for a hard interface
* in debugfs.
* @hard_iface: hard interface which is deleted.
--- a/net/batman-adv/debugfs.h
+++ b/net/batman-adv/debugfs.h
@@ -32,6 +32,7 @@ void batadv_debugfs_destroy(void);
int batadv_debugfs_add_meshif(struct net_device *dev);
void batadv_debugfs_del_meshif(struct net_device *dev);
int batadv_debugfs_add_hardif(struct batadv_hard_iface *hard_iface);
+void batadv_debugfs_rename_hardif(struct batadv_hard_iface *hard_iface);
void batadv_debugfs_del_hardif(struct batadv_hard_iface *hard_iface);

#else
@@ -60,6 +61,11 @@ int batadv_debugfs_add_hardif(struct bat
}

static inline
+void batadv_debugfs_rename_hardif(struct batadv_hard_iface *hard_iface)
+{
+}
+
+static inline
void batadv_debugfs_del_hardif(struct batadv_hard_iface *hard_iface)
{
}
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -1051,6 +1051,9 @@ static int batadv_hard_if_event(struct n
if (batadv_is_wifi_hardif(hard_iface))
hard_iface->num_bcasts = BATADV_NUM_BCASTS_WIRELESS;
break;
+ case NETDEV_CHANGENAME:
+ batadv_debugfs_rename_hardif(hard_iface);
+ break;
default:
break;
}