netfilter: xtables: avoid pointer to self

Commit 784544739a25c30637397ace5489eeb6e15d7d49 (netfilter: iptables:
lock free counters) broke a number of modules whose rule data referenced
itself. A reallocation would not reestablish the correct references, so
it is best to use a separate struct that does not fall under RCU.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>

3 files changed, 76 insertions, 23 deletions

diff --git a/net/netfilter/xt_limit.c b/net/netfilter/xt_limit.c
index c908d69a5595..2e8089ecd0af 100644
--- a/net/netfilter/xt_limit.c
+++ b/net/netfilter/xt_limit.c
@@ -14,6 +14,11 @@
 #include <linux/netfilter/x_tables.h>
 #include <linux/netfilter/xt_limit.h>
 
+struct xt_limit_priv {
+        unsigned long prev;
+        uint32_t credit;
+};
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Herve Eychenne <rv@wallfire.org>");
 MODULE_DESCRIPTION("Xtables: rate-limit match");
@@ -60,18 +65,18 @@ static DEFINE_SPINLOCK(limit_lock);
 static bool
 limit_mt(const struct sk_buff *skb, const struct xt_match_param *par)
 {
-        struct xt_rateinfo *r =
-                ((const struct xt_rateinfo *)par->matchinfo)->master;
+        const struct xt_rateinfo *r = par->matchinfo;
+        struct xt_limit_priv *priv = r->master;
         unsigned long now = jiffies;
 
         spin_lock_bh(&limit_lock);
-        r->credit += (now - xchg(&r->prev, now)) * CREDITS_PER_JIFFY;
-        if (r->credit > r->credit_cap)
-                r->credit = r->credit_cap;
+        priv->credit += (now - xchg(&priv->prev, now)) * CREDITS_PER_JIFFY;
+        if (priv->credit > r->credit_cap)
+                priv->credit = r->credit_cap;
 
-        if (r->credit >= r->cost) {
+        if (priv->credit >= r->cost) {
                 /* We're not limited. */
-                r->credit -= r->cost;
+                priv->credit -= r->cost;
                 spin_unlock_bh(&limit_lock);
                 return true;
         }
@@ -95,6 +100,7 @@ user2credits(u_int32_t user)
 static bool limit_mt_check(const struct xt_mtchk_param *par)
 {
         struct xt_rateinfo *r = par->matchinfo;
+        struct xt_limit_priv *priv;
 
         /* Check for overflow. */
         if (r->burst == 0
@@ -104,19 +110,30 @@ static bool limit_mt_check(const struct xt_mtchk_param *par)
                 return false;
         }
 
-        /* For SMP, we only want to use one set of counters. */
-        r->master = r;
+        priv = kmalloc(sizeof(*priv), GFP_KERNEL);
+        if (priv == NULL)
+                return -ENOMEM;
+
+        /* For SMP, we only want to use one set of state. */
+        r->master = priv;
         if (r->cost == 0) {
                 /* User avg in seconds * XT_LIMIT_SCALE: convert to jiffies *
                    128. */
-                r->prev = jiffies;
-                r->credit = user2credits(r->avg * r->burst);     /* Credits full. */
+                priv->prev = jiffies;
+                priv->credit = user2credits(r->avg * r->burst); /* Credits full. */
                 r->credit_cap = user2credits(r->avg * r->burst); /* Credits full. */
                 r->cost = user2credits(r->avg);
         }
         return true;
 }
 
+static void limit_mt_destroy(const struct xt_mtdtor_param *par)
+{
+        const struct xt_rateinfo *info = par->matchinfo;
+
+        kfree(info->master);
+}
+
 #ifdef CONFIG_COMPAT
 struct compat_xt_rateinfo {
         u_int32_t avg;
@@ -167,6 +184,7 @@ static struct xt_match limit_mt_reg __read_mostly = {
         .family           = NFPROTO_UNSPEC,
         .match            = limit_mt,
         .checkentry       = limit_mt_check,
+        .destroy          = limit_mt_destroy,
         .matchsize        = sizeof(struct xt_rateinfo),
 #ifdef CONFIG_COMPAT
         .compatsize       = sizeof(struct compat_xt_rateinfo),
diff --git a/net/netfilter/xt_quota.c b/net/netfilter/xt_quota.c
index c84fce5e0f3e..01dd07b764ec 100644
--- a/net/netfilter/xt_quota.c
+++ b/net/netfilter/xt_quota.c
@@ -9,6 +9,10 @@
 #include <linux/netfilter/x_tables.h>
 #include <linux/netfilter/xt_quota.h>
 
+struct xt_quota_priv {
+        uint64_t quota;
+};
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
 MODULE_DESCRIPTION("Xtables: countdown quota match");
@@ -20,18 +24,20 @@ static DEFINE_SPINLOCK(quota_lock);
 static bool
 quota_mt(const struct sk_buff *skb, const struct xt_match_param *par)
 {
-        struct xt_quota_info *q =
-                ((const struct xt_quota_info *)par->matchinfo)->master;
+        struct xt_quota_info *q = (void *)par->matchinfo;
+        struct xt_quota_priv *priv = q->master;
         bool ret = q->flags & XT_QUOTA_INVERT;
 
         spin_lock_bh(&quota_lock);
-        if (q->quota >= skb->len) {
-                q->quota -= skb->len;
+        if (priv->quota >= skb->len) {
+                priv->quota -= skb->len;
                 ret = !ret;
         } else {
                 /* we do not allow even small packets from now on */
-                q->quota = 0;
+                priv->quota = 0;
         }
+        /* Copy quota back to matchinfo so that iptables can display it */
+        q->quota = priv->quota;
         spin_unlock_bh(&quota_lock);
 
         return ret;
@@ -43,17 +49,28 @@ static bool quota_mt_check(const struct xt_mtchk_param *par)
 
         if (q->flags & ~XT_QUOTA_MASK)
                 return false;
-        /* For SMP, we only want to use one set of counters. */
-        q->master = q;
+
+        q->master = kmalloc(sizeof(*q->master), GFP_KERNEL);
+        if (q->master == NULL)
+                return -ENOMEM;
+
         return true;
 }
 
+static void quota_mt_destroy(const struct xt_mtdtor_param *par)
+{
+        const struct xt_quota_info *q = par->matchinfo;
+
+        kfree(q->master);
+}
+
 static struct xt_match quota_mt_reg __read_mostly = {
         .name       = "quota",
         .revision   = 0,
         .family     = NFPROTO_UNSPEC,
         .match      = quota_mt,
         .checkentry = quota_mt_check,
+        .destroy    = quota_mt_destroy,
         .matchsize  = sizeof(struct xt_quota_info),
         .me         = THIS_MODULE,
 };
diff --git a/net/netfilter/xt_statistic.c b/net/netfilter/xt_statistic.c
index 0d75141139d5..d8c0f8f1a78e 100644
--- a/net/netfilter/xt_statistic.c
+++ b/net/netfilter/xt_statistic.c
@@ -16,6 +16,10 @@
 #include <linux/netfilter/xt_statistic.h>
 #include <linux/netfilter/x_tables.h>
 
+struct xt_statistic_priv {
+        uint32_t count;
+};
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
 MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)");
@@ -27,7 +31,7 @@ static DEFINE_SPINLOCK(nth_lock);
 static bool
 statistic_mt(const struct sk_buff *skb, const struct xt_match_param *par)
 {
-        struct xt_statistic_info *info = (void *)par->matchinfo;
+        const struct xt_statistic_info *info = par->matchinfo;
         bool ret = info->flags & XT_STATISTIC_INVERT;
 
         switch (info->mode) {
@@ -36,10 +40,9 @@ statistic_mt(const struct sk_buff *skb, const struct xt_match_param *par)
                         ret = !ret;
                 break;
         case XT_STATISTIC_MODE_NTH:
-                info = info->master;
                 spin_lock_bh(&nth_lock);
-                if (info->u.nth.count++ == info->u.nth.every) {
-                        info->u.nth.count = 0;
+                if (info->master->count++ == info->u.nth.every) {
+                        info->master->count = 0;
                         ret = !ret;
                 }
                 spin_unlock_bh(&nth_lock);
@@ -56,16 +59,31 @@ static bool statistic_mt_check(const struct xt_mtchk_param *par)
         if (info->mode > XT_STATISTIC_MODE_MAX ||
             info->flags & ~XT_STATISTIC_MASK)
                 return false;
-        info->master = info;
+
+        info->master = kzalloc(sizeof(*info->master), GFP_KERNEL);
+        if (info->master == NULL) {
+                printk(KERN_ERR KBUILD_MODNAME ": Out of memory\n");
+                return false;
+        }
+        info->master->count = info->u.nth.count;
+
         return true;
 }
 
+static void statistic_mt_destroy(const struct xt_mtdtor_param *par)
+{
+        const struct xt_statistic_info *info = par->matchinfo;
+
+        kfree(info->master);
+}
+
 static struct xt_match xt_statistic_mt_reg __read_mostly = {
         .name       = "statistic",
         .revision   = 0,
         .family     = NFPROTO_UNSPEC,
         .match      = statistic_mt,
         .checkentry = statistic_mt_check,
+        .destroy    = statistic_mt_destroy,
         .matchsize  = sizeof(struct xt_statistic_info),
         .me         = THIS_MODULE,
 };