[PKT_SCHED]: GRED: Use a central table definition change procedure

Introduces a function gred_change_table_def() acting as a central
point to change the table definition.

Adds missing validations for table definition: MAX_DPs > DPs > 0
and def_DP < DPs thus fixing possible invalid memory reference
oopses. Only root could do it but having a typo crashing the
machine is a bit hard.

Adds missing locking while changing the table definition, the
operation of changing the number of DPs and removing shadowed VQs
may not be interrupted by a dequeue.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>

1 files changed, 61 insertions, 52 deletions

diff --git a/net/sched/sch_gred.c b/net/sched/sch_gred.c
index a1369550ce78..fdc20ced52ef 100644
--- a/net/sched/sch_gred.c
+++ b/net/sched/sch_gred.c
@@ -378,43 +378,72 @@ static void gred_reset(struct Qdisc* sch)
         }
 }
 
-static int gred_change(struct Qdisc *sch, struct rtattr *opt)
+static inline void gred_destroy_vq(struct gred_sched_data *q)
+{
+        kfree(q);
+}
+
+static inline int gred_change_table_def(struct Qdisc *sch, struct rtattr *dps)
 {
         struct gred_sched *table = qdisc_priv(sch);
-        struct gred_sched_data *q;
-        struct tc_gred_qopt *ctl;
         struct tc_gred_sopt *sopt;
-        struct rtattr *tb[TCA_GRED_STAB];
-        struct rtattr *tb2[TCA_GRED_DPS];
+        int i;
 
-        if (opt == NULL || rtattr_parse_nested(tb, TCA_GRED_STAB, opt))
+        if (dps == NULL || RTA_PAYLOAD(dps) < sizeof(*sopt))
                 return -EINVAL;
 
-        if (tb[TCA_GRED_PARMS-1] == 0 && tb[TCA_GRED_STAB-1] == 0) {
-                rtattr_parse_nested(tb2, TCA_GRED_DPS, opt);
+        sopt = RTA_DATA(dps);
 
-            if (tb2[TCA_GRED_DPS-1] == 0) 
-                        return -EINVAL;
+        if (sopt->DPs > MAX_DPs || sopt->DPs == 0 || sopt->def_DP >= sopt->DPs)
+                return -EINVAL;
 
-                sopt = RTA_DATA(tb2[TCA_GRED_DPS-1]);
-                table->DPs=sopt->DPs;   
-                table->def=sopt->def_DP; 
+        sch_tree_lock(sch);
+        table->DPs = sopt->DPs;
+        table->def = sopt->def_DP;
 
-                if (sopt->grio) {
-                        gred_enable_rio_mode(table);
-                        gred_disable_wred_mode(table);
-                        if (gred_wred_mode_check(sch))
-                                gred_enable_wred_mode(table);
-                } else {
-                        gred_disable_rio_mode(table);
-                        gred_disable_wred_mode(table);
-                }
+        /*
+         * Every entry point to GRED is synchronized with the above code
+         * and the DP is checked against DPs, i.e. shadowed VQs can no
+         * longer be found so we can unlock right here.
+         */
+        sch_tree_unlock(sch);
 
-                table->initd=0;
-                /* probably need to clear all the table DP entries as well */
-                return 0;
-            }
+        if (sopt->grio) {
+                gred_enable_rio_mode(table);
+                gred_disable_wred_mode(table);
+                if (gred_wred_mode_check(sch))
+                        gred_enable_wred_mode(table);
+        } else {
+                gred_disable_rio_mode(table);
+                gred_disable_wred_mode(table);
+        }
+
+        for (i = table->DPs; i < MAX_DPs; i++) {
+                if (table->tab[i]) {
+                        printk(KERN_WARNING "GRED: Warning: Destroying "
+                               "shadowed VQ 0x%x\n", i);
+                        gred_destroy_vq(table->tab[i]);
+                        table->tab[i] = NULL;
+                }
+        }
 
+        table->initd = 0;
+
+        return 0;
+}
+
+static int gred_change(struct Qdisc *sch, struct rtattr *opt)
+{
+        struct gred_sched *table = qdisc_priv(sch);
+        struct gred_sched_data *q;
+        struct tc_gred_qopt *ctl;
+        struct rtattr *tb[TCA_GRED_STAB];
+
+        if (opt == NULL || rtattr_parse_nested(tb, TCA_GRED_STAB, opt))
+                return -EINVAL;
+
+        if (tb[TCA_GRED_PARMS-1] == NULL && tb[TCA_GRED_STAB-1] == NULL)
+                return gred_change_table_def(sch, tb[TCA_GRED_DPS-1]);
 
         if (!table->DPs || tb[TCA_GRED_PARMS-1] == 0 || tb[TCA_GRED_STAB-1] == 0 ||
                 RTA_PAYLOAD(tb[TCA_GRED_PARMS-1]) < sizeof(*ctl) ||
@@ -526,35 +555,15 @@ static int gred_change(struct Qdisc *sch, struct rtattr *opt)
 
 static int gred_init(struct Qdisc *sch, struct rtattr *opt)
 {
-        struct gred_sched *table = qdisc_priv(sch);
-        struct tc_gred_sopt *sopt;
-        struct rtattr *tb[TCA_GRED_STAB];
-        struct rtattr *tb2[TCA_GRED_DPS];
+        struct rtattr *tb[TCA_GRED_MAX];
 
-        if (opt == NULL || rtattr_parse_nested(tb, TCA_GRED_STAB, opt))
+        if (opt == NULL || rtattr_parse_nested(tb, TCA_GRED_MAX, opt))
                 return -EINVAL;
 
-        if (tb[TCA_GRED_PARMS-1] == 0 && tb[TCA_GRED_STAB-1] == 0) {
-                rtattr_parse_nested(tb2, TCA_GRED_DPS, opt);
-
-            if (tb2[TCA_GRED_DPS-1] == 0) 
-                        return -EINVAL;
-
-                sopt = RTA_DATA(tb2[TCA_GRED_DPS-1]);
-                table->DPs=sopt->DPs;   
-                table->def=sopt->def_DP; 
-
-                if (sopt->grio)
-                        gred_enable_rio_mode(table);
-                else
-                        gred_disable_rio_mode(table);
-
-                table->initd=0;
-                return 0;
-        }
+        if (tb[TCA_GRED_PARMS-1] || tb[TCA_GRED_STAB-1])
+                return -EINVAL;
 
-        DPRINTK("\n GRED_INIT error!\n");
-        return -EINVAL;
+        return gred_change_table_def(sch, tb[TCA_GRED_DPS-1]);
 }
 
 static int gred_dump(struct Qdisc *sch, struct sk_buff *skb)
@@ -641,7 +650,7 @@ static void gred_destroy(struct Qdisc *sch)
 
         for (i = 0;i < table->DPs; i++) {
                 if (table->tab[i])
-                        kfree(table->tab[i]);
+                        gred_destroy_vq(table->tab[i]);
         }
 }