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

[ Upstream commit 696ecdc10622d86541f2e35cc16e15b6b3b1b67e ]

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/sched/act_gact.c b/net/sched/act_gact.c
index b77f5a0..bdacd8d 100644 (file)
--- 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;