[Patch net-next] net_sched: fix a potential out-of-bound access

[Cong Wang]

In tca_action_gd(), when tcf_action_get_1() fails in the middle
of the loop, tcf_action_put_many(&actions[acts_deleted]) is
called to cleanup.

But inside tcf_action_put_many() it still iterates from
0 to TCA_ACT_MAX_PRIO, so inside it would be:

&actions[acts_deleted][0]...&actions[acts_deleted][MAX_PRIO]

Then the overall of the result is:

actions[acts_deleted]...actions[acts_deleted + MAX_PRIO]

We have a potential out-of-bound access when acts_deleted > 1.

acts_deleted is completely unnecessary since tcf_action_put_many()
checks against NULL pointer.

Fixes: 90b73b77d08e ("net: sched: change action API to use array of pointers to 
actions")
Cc: Jiri Pirko <j...@mellanox.com>
Cc: Vlad Buslov <vla...@mellanox.com>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
---
 net/sched/act_api.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 229d63c99be2..36549bc7ce78 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -1176,7 +1176,7 @@ static int tca_action_flush(struct net *net, struct 
nlattr *nla,
 }
 
 static int tcf_action_delete(struct net *net, struct tc_action *actions[],
-                            int *acts_deleted, struct netlink_ext_ack *extack)
+                            struct netlink_ext_ack *extack)
 {
        u32 act_index;
        int ret, i;
@@ -1196,20 +1196,16 @@ static int tcf_action_delete(struct net *net, struct 
tc_action *actions[],
                } else  {
                        /* now do the delete */
                        ret = ops->delete(net, act_index);
-                       if (ret < 0) {
-                               *acts_deleted = i + 1;
+                       if (ret < 0)
                                return ret;
-                       }
                }
        }
-       *acts_deleted = i;
        return 0;
 }
 
 static int
 tcf_del_notify(struct net *net, struct nlmsghdr *n, struct tc_action 
*actions[],
-              int *acts_deleted, u32 portid, size_t attr_size,
-              struct netlink_ext_ack *extack)
+              u32 portid, size_t attr_size, struct netlink_ext_ack *extack)
 {
        int ret;
        struct sk_buff *skb;
@@ -1227,7 +1223,7 @@ tcf_del_notify(struct net *net, struct nlmsghdr *n, 
struct tc_action *actions[],
        }
 
        /* now do the delete */
-       ret = tcf_action_delete(net, actions, acts_deleted, extack);
+       ret = tcf_action_delete(net, actions, extack);
        if (ret < 0) {
                NL_SET_ERR_MSG(extack, "Failed to delete TC action");
                kfree_skb(skb);
@@ -1250,7 +1246,6 @@ tca_action_gd(struct net *net, struct nlattr *nla, struct 
nlmsghdr *n,
        struct tc_action *act;
        size_t attr_size = 0;
        struct tc_action *actions[TCA_ACT_MAX_PRIO + 1] = {};
-       int acts_deleted = 0;
 
        ret = nla_parse_nested(tb, TCA_ACT_MAX_PRIO, nla, NULL, extack);
        if (ret < 0)
@@ -1280,14 +1275,14 @@ tca_action_gd(struct net *net, struct nlattr *nla, 
struct nlmsghdr *n,
        if (event == RTM_GETACTION)
                ret = tcf_get_notify(net, portid, n, actions, event, extack);
        else { /* delete */
-               ret = tcf_del_notify(net, n, actions, &acts_deleted, portid,
+               ret = tcf_del_notify(net, n, actions, portid,
                                     attr_size, extack);
                if (ret)
                        goto err;
                return ret;
        }
 err:
-       tcf_action_put_many(&actions[acts_deleted]);
+       tcf_action_put_many(actions);
        return ret;
 }
 
-- 
2.14.4