netfilter: xtables: avoid pointer to self

Commit 7845447 (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 <[email protected]>
Signed-off-by: Patrick McHardy <[email protected]>

Author: Jan Engelhardt

include/linux/netfilter/xt_limit.h

@@ -4,18 +4,19 @@
 /* timings are in milliseconds. */
 #define XT_LIMIT_SCALE 10000
 
+struct xt_limit_priv;
+
 /* 1/10,000 sec period => max of 10,000/sec.  Min rate is then 429490
    seconds, or one every 59 hours. */
 struct xt_rateinfo {
 	u_int32_t avg;    /* Average secs between packets * scale */
 	u_int32_t burst;  /* Period multiplier for upper limit. */
 
 	/* Used internally by the kernel */
-	unsigned long prev;
-	u_int32_t credit;
+	unsigned long prev; /* moved to xt_limit_priv */
+	u_int32_t credit; /* moved to xt_limit_priv */
 	u_int32_t credit_cap, cost;
 
-	/* Ugly, ugly fucker. */
-	struct xt_rateinfo *master;
+	struct xt_limit_priv *master;
 };
 #endif /*_XT_RATE_H*/

include/linux/netfilter/xt_quota.h

@@ -6,13 +6,15 @@ enum xt_quota_flags {
 };
 #define XT_QUOTA_MASK		0x1
 
+struct xt_quota_priv;
+
 struct xt_quota_info {
 	u_int32_t		flags;
 	u_int32_t		pad;
 
 	/* Used internally by the kernel */
 	aligned_u64		quota;
-	struct xt_quota_info	*master;
+	struct xt_quota_priv	*master;
 };
 
 #endif /* _XT_QUOTA_H */

include/linux/netfilter/xt_statistic.h

@@ -13,6 +13,8 @@ enum xt_statistic_flags {
 };
 #define XT_STATISTIC_MASK		0x1
 
+struct xt_statistic_priv;
+
 struct xt_statistic_info {
 	u_int16_t			mode;
 	u_int16_t			flags;
@@ -23,11 +25,10 @@ struct xt_statistic_info {
 		struct {
 			u_int32_t	every;
 			u_int32_t	packet;
-			/* Used internally by the kernel */
-			u_int32_t	count;
+			u_int32_t	count; /* unused */
 		} nth;
 	} u;
-	struct xt_statistic_info	*master __attribute__((aligned(8)));
+	struct xt_statistic_priv *master __attribute__((aligned(8)));
 };
 
 #endif /* _XT_STATISTIC_H */

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 <[email protected]>");
 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),

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 <[email protected]>");
 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,
 };

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 <[email protected]>");
 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,
 };