[PATCH] net: cgroup: fix out of bounds accesses

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

dev->priomap is allocated by extend_netdev_table() called from
update_netdev_tables().
And this is only called if write_priomap() is called.

But if write_priomap() is not called, it seems we can have out of bounds
accesses in cgrp_destroy(), read_priomap() & skb_update_prio()

With help from Gao Feng

Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: Neil Horman <nhor...@tuxdriver.com>
Cc: Gao feng <gaof...@cn.fujitsu.com>
---
net/core/dev.c            |    8 ++++++--
net/core/netprio_cgroup.c |    4 ++--
2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 84f01ba..0f28a9e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2444,8 +2444,12 @@ static void skb_update_prio(struct sk_buff *skb)
 {
        struct netprio_map *map = rcu_dereference_bh(skb->dev->priomap);
 
-       if ((!skb->priority) && (skb->sk) && map)
-               skb->priority = map->priomap[skb->sk->sk_cgrp_prioidx];
+       if (!skb->priority && skb->sk && map) {
+               unsigned int prioidx = skb->sk->sk_cgrp_prioidx;
+
+               if (prioidx < map->priomap_len)
+                       skb->priority = map->priomap[prioidx];
+       }
 }
 #else
 #define skb_update_prio(skb)
diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index aa907ed..3e953ea 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -142,7 +142,7 @@ static void cgrp_destroy(struct cgroup *cgrp)
        rtnl_lock();
        for_each_netdev(&init_net, dev) {
                map = rtnl_dereference(dev->priomap);
-               if (map)
+               if (map && cs->prioidx < map->priomap_len)
                        map->priomap[cs->prioidx] = 0;
        }
        rtnl_unlock();
@@ -166,7 +166,7 @@ static int read_priomap(struct cgroup *cont, struct cftype 
*cft,
        rcu_read_lock();
        for_each_netdev_rcu(&init_net, dev) {
                map = rcu_dereference(dev->priomap);
-               priority = map ? map->priomap[prioidx] : 0;
+               priority = (map && prioidx < map->priomap_len) ? 
map->priomap[prioidx] : 0;
                cb->fill(cb, dev->name, priority);
        }
        rcu_read_unlock();


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