net_sched: gact: Fix potential panic in tcf_gact().

gact_rand array is accessed by gact->tcfg_ptype whose value
is assumed to less than MAX_RAND, but any range checks are
not performed.

So add a check in tcf_gact_init(). And in tcf_gact(), we can
reduce a branch.

Signed-off-by: Hiroaki SHIMODA <shimoda.hiroaki@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 3 deletions

diff --git a/net/sched/act_gact.c b/net/sched/act_gact.c
index f10fb8256442..05d60859d8e3 100644
--- a/net/sched/act_gact.c
+++ b/net/sched/act_gact.c
@@ -67,6 +67,9 @@ static int tcf_gact_init(struct nlattr *nla, struct nlattr *est,
         struct tcf_common *pc;
         int ret = 0;
         int err;
+#ifdef CONFIG_GACT_PROB
+        struct tc_gact_p *p_parm = NULL;
+#endif
 
         if (nla == NULL)
                 return -EINVAL;
@@ -82,6 +85,12 @@ static int tcf_gact_init(struct nlattr *nla, struct nlattr *est,
 #ifndef CONFIG_GACT_PROB
         if (tb[TCA_GACT_PROB] != NULL)
                 return -EOPNOTSUPP;
+#else
+        if (tb[TCA_GACT_PROB]) {
+                p_parm = nla_data(tb[TCA_GACT_PROB]);
+                if (p_parm->ptype >= MAX_RAND)
+                        return -EINVAL;
+        }
 #endif
 
         pc = tcf_hash_check(parm->index, a, bind, &gact_hash_info);
@@ -103,8 +112,7 @@ static int tcf_gact_init(struct nlattr *nla, struct nlattr *est,
         spin_lock_bh(&gact->tcf_lock);
         gact->tcf_action = parm->action;
 #ifdef CONFIG_GACT_PROB
-        if (tb[TCA_GACT_PROB] != NULL) {
-                struct tc_gact_p *p_parm = nla_data(tb[TCA_GACT_PROB]);
+        if (p_parm) {
                 gact->tcfg_paction = p_parm->paction;
                 gact->tcfg_pval    = p_parm->pval;
                 gact->tcfg_ptype   = p_parm->ptype;
@@ -133,7 +141,7 @@ static int tcf_gact(struct sk_buff *skb, const struct tc_action *a,
 
         spin_lock(&gact->tcf_lock);
 #ifdef CONFIG_GACT_PROB
-        if (gact->tcfg_ptype && gact_rand[gact->tcfg_ptype] != NULL)
+        if (gact->tcfg_ptype)
                 action = gact_rand[gact->tcfg_ptype](gact);
         else
                 action = gact->tcf_action;