[PATCH v3] net: cgroup: fix access the unallocated memory in netprio cgroup

Gao feng
2012-07-11T08:30:06Z

there are some out of bound accesses in netprio cgroup.

now before accessing the dev->priomap.priomap array,we only check
if the dev->priomap exist.and because we don't want to see
additional bound checkings in fast path, so we should make sure
that dev->priomap is null or array size of dev->priomap.priomap
is equal to max_prioidx + 1;

and it's not needed to call extend_netdev_tabel in write_priomap,
we can only allocate the net device's priomap which we change through
net_prio.ifpriomap.

this patch add a return value for update_netdev_tables & extend_netdev_table,
so when new_priomap is allocated failed,write_priomap will stop to access
the priomap,and return -ENOMEM back to the userspace to tell the user
what happend.

Change From v2:
1. protect extend_netdev_table by RTNL.
2. when extend_netdev_table failed,call dev_put to reduce device's refcount.

Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Eric Dumazet <edumazet@google.com>
---
net/core/netprio_cgroup.c | 54 ++++++++++++++++++++++++++++++++------------
1 files changed, 39 insertions(+), 15 deletions(-)

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index aa907ed..05b961d 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -65,7 +65,7 @@ static void put_prioidx(u32 idx)
spin_unlock_irqrestore(&prioidx_map_lock, flags);
}

-static void extend_netdev_table(struct net_device *dev, u32 new_len)
+static int extend_netdev_table(struct net_device *dev, u32 new_len)
{
size_t new_size = sizeof(struct netprio_map) +
((sizeof(u32) * new_len));
@@ -77,7 +77,7 @@ static void extend_netdev_table(struct net_device *dev, u32 new_len)

if (!new_priomap) {
pr_warn("Unable to alloc new priomap!\n");
- return;
+ return -ENOMEM;
}

for (i = 0;
@@ -90,10 +90,12 @@ static void extend_netdev_table(struct net_device *dev, u32 new_len)
rcu_assign_pointer(dev->priomap, new_priomap);
if (old_priomap)
kfree_rcu(old_priomap, rcu);
+ return 0;
}

-static void update_netdev_tables(void)
+static int update_netdev_tables(void)
{
+ int ret = 0;
struct net_device *dev;
u32 max_len = atomic_read(&max_prioidx) + 1;
struct netprio_map *map;
@@ -101,35 +103,49 @@ static void update_netdev_tables(void)
rtnl_lock();
for_each_netdev(&init_net, dev) {
map = rtnl_dereference(dev->priomap);
- if ((!map) ||
- (map->priomap_len < max_len))
- extend_netdev_table(dev, max_len);
+ /*
+ * don't allocate priomap if we didn't
+ * change net_prio.ifpriomap,this will
+ * speed up skb_update_prio.
+ */
+ if (map) {
+ ret = extend_netdev_table(dev, max_len);
+ if (ret < 0)
+ break;
+ }
}
rtnl_unlock();
+ return ret;
}

static struct cgroup_subsys_state *cgrp_create(struct cgroup *cgrp)
{
struct cgroup_netprio_state *cs;
- int ret;
+ int ret = -EINVAL;

cs = kzalloc(sizeof(*cs), GFP_KERNEL);
if (!cs)
return ERR_PTR(-ENOMEM);

- if (cgrp->parent && cgrp_netprio_state(cgrp->parent)->prioidx) {
- kfree(cs);
- return ERR_PTR(-EINVAL);
- }
+ if (cgrp->parent && cgrp_netprio_state(cgrp->parent)->prioidx)
+ goto out;

ret = get_prioidx(&cs->prioidx);
- if (ret != 0) {
+ if (ret < 0) {
pr_warn("No space in priority index array\n");
- kfree(cs);
- return ERR_PTR(ret);
+ goto out;
+ }
+
+ ret = update_netdev_tables();
+ if (ret < 0) {
+ put_prioidx(cs->prioidx);
+ goto out;
}

return &cs->css;
+out:
+ kfree(cs);
+ return ERR_PTR(ret);
}

static void cgrp_destroy(struct cgroup *cgrp)
@@ -179,6 +195,7 @@ static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
char *devname = kstrdup(buffer, GFP_KERNEL);
int ret = -EINVAL;
u32 prioidx = cgrp_netprio_state(cgrp)->prioidx;
+ u32 max_len = atomic_read(&max_prioidx) + 1;
unsigned long priority;
char *priostr;
struct net_device *dev;
@@ -221,13 +238,20 @@ static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
if (!dev)
goto out_free_devname;

- update_netdev_tables();
+ rtnl_lock();
+ ret = extend_netdev_table(dev, max_len);
+ rtnl_unlock();
+ if (ret < 0)
+ goto out_put_dev;
+
ret = 0;
rcu_read_lock();
map = rcu_dereference(dev->priomap);
if (map)
map->priomap[prioidx] = priority;
rcu_read_unlock();
+
+out_put_dev:
dev_put(dev);

out_free_devname:
--
1.7.7.6