[PATCH AUTOSEL 4.14 04/32] batman-adv: Fix segfault when writing to sysfs elp_interval

Sasha Levin
2018-10-08T15:26:38Z

From: Sven Eckelmann <sven@narfation.org>

[ Upstream commit a25bab9d723a08bd0bdafb1529faf9094c690b70 ]

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
net/batman-adv/sysfs.c | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/net/batman-adv/sysfs.c b/net/batman-adv/sysfs.c
index ec412c5b8697..2ef9b136fc39 100644
--- a/net/batman-adv/sysfs.c
+++ b/net/batman-adv/sysfs.c
@@ -186,7 +186,8 @@ 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) \
@@ -260,7 +261,9 @@ 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; \
@@ -354,10 +357,12 @@ __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;

@@ -383,8 +388,11 @@ 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;
@@ -395,12 +403,13 @@ 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);

@@ -569,7 +578,7 @@ 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,
--
2.17.1