batman-adv: Fix segfault when writing to sysfs elp_interval

The per hardif sysfs file "batman_adv/elp_interval" is using the generic
functions to store/show uint values. The helper __batadv_store_uint_attr
requires the softif net_device as parameter to print the resulting change
as info text when the users writes to this file. It uses the helper
function batadv_info to add it at the same time to the kernel ring buffer
and to the batman-adv debug log (when CONFIG_BATMAN_ADV_DEBUG is enabled).

The function batadv_info requires as first parameter the batman-adv softif
net_device. This parameter is then used to find the private buffer which
contains the debug log for this batman-adv interface. But
batadv_store_throughput_override used as first argument the slave
net_device. This slave device doesn't have the batadv_priv private data
which is access by batadv_info.

Writing to this file with CONFIG_BATMAN_ADV_DEBUG enabled can either lead
to a segfault or to memory corruption.

Fixes: 0744ff8fa8fa ("batman-adv: Add hard_iface specific sysfs wrapper macros for UINT")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Acked-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

1 files changed, 17 insertions, 8 deletions

diff --git a/net/batman-adv/sysfs.c b/net/batman-adv/sysfs.c
index 3a76e8970c02..09427fc6494a 100644
--- a/net/batman-adv/sysfs.c
+++ b/net/batman-adv/sysfs.c
@@ -188,7 +188,8 @@ ssize_t batadv_store_##_name(struct kobject *kobj,			\
                                                                         \
         return __batadv_store_uint_attr(buff, count, _min, _max,        \
                                         _post_func, attr,               \
-                                        &bat_priv->_var, net_dev);      \
+                                        &bat_priv->_var, net_dev,       \
+                                        NULL);  \
 }
 
 #define BATADV_ATTR_SIF_SHOW_UINT(_name, _var)                          \
@@ -262,7 +263,9 @@ ssize_t batadv_store_##_name(struct kobject *kobj,			\
                                                                         \
         length = __batadv_store_uint_attr(buff, count, _min, _max,      \
                                           _post_func, attr,             \
-                                          &hard_iface->_var, net_dev);  \
+                                          &hard_iface->_var,            \
+                                          hard_iface->soft_iface,       \
+                                          net_dev);                     \
                                                                         \
         batadv_hardif_put(hard_iface);                          \
         return length;                                                  \
@@ -356,10 +359,12 @@ __batadv_store_bool_attr(char *buff, size_t count,
 
 static int batadv_store_uint_attr(const char *buff, size_t count,
                                   struct net_device *net_dev,
+                                  struct net_device *slave_dev,
                                   const char *attr_name,
                                   unsigned int min, unsigned int max,
                                   atomic_t *attr)
 {
+        char ifname[IFNAMSIZ + 3] = "";
         unsigned long uint_val;
         int ret;
 
@@ -385,8 +390,11 @@ static int batadv_store_uint_attr(const char *buff, size_t count,
         if (atomic_read(attr) == uint_val)
                 return count;
 
-        batadv_info(net_dev, "%s: Changing from: %i to: %lu\n",
-                    attr_name, atomic_read(attr), uint_val);
+        if (slave_dev)
+                snprintf(ifname, sizeof(ifname), "%s: ", slave_dev->name);
+
+        batadv_info(net_dev, "%s: %sChanging from: %i to: %lu\n",
+                    attr_name, ifname, atomic_read(attr), uint_val);
 
         atomic_set(attr, uint_val);
         return count;
@@ -397,12 +405,13 @@ static ssize_t __batadv_store_uint_attr(const char *buff, size_t count,
                                         void (*post_func)(struct net_device *),
                                         const struct attribute *attr,
                                         atomic_t *attr_store,
-                                        struct net_device *net_dev)
+                                        struct net_device *net_dev,
+                                        struct net_device *slave_dev)
 {
         int ret;
 
-        ret = batadv_store_uint_attr(buff, count, net_dev, attr->name, min, max,
-                                     attr_store);
+        ret = batadv_store_uint_attr(buff, count, net_dev, slave_dev,
+                                     attr->name, min, max, attr_store);
         if (post_func && ret)
                 post_func(net_dev);
 
@@ -571,7 +580,7 @@ static ssize_t batadv_store_gw_sel_class(struct kobject *kobj,
         return __batadv_store_uint_attr(buff, count, 1, BATADV_TQ_MAX_VALUE,
                                         batadv_post_gw_reselect, attr,
                                         &bat_priv->gw.sel_class,
-                                        bat_priv->soft_iface);
+                                        bat_priv->soft_iface, NULL);
 }
 
 static ssize_t batadv_show_gw_bwidth(struct kobject *kobj,