[NETFILTER]: x_tables: simplify compat API

Split the xt_compat_match/xt_compat_target into smaller type-safe functions
performing just one operation. Handle all alignment and size-related
conversions centrally in these function instead of requiring each module to
implement a full-blown conversion function. Replace ->compat callback by
->compat_from_user and ->compat_to_user callbacks, responsible for
converting just a single private structure.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 151 insertions, 185 deletions

diff --git a/include/linux/netfilter/x_tables.h b/include/linux/netfilter/x_tables.h
index c832295dbf6..739a98eebe2 100644
--- a/include/linux/netfilter/x_tables.h
+++ b/include/linux/netfilter/x_tables.h
@@ -138,12 +138,6 @@ struct xt_counters_info
 
 #include <linux/netdevice.h>
 
-#ifdef CONFIG_COMPAT
-#define COMPAT_TO_USER		1
-#define COMPAT_FROM_USER	-1
-#define COMPAT_CALC_SIZE	0
-#endif
-
 struct xt_match
 {
 	struct list_head list;
@@ -176,7 +170,8 @@ struct xt_match
 	void (*destroy)(const struct xt_match *match, void *matchinfo);
 
 	/* Called when userspace align differs from kernel space one */
-	int (*compat)(void *match, void **dstptr, int *size, int convert);
+	void (*compat_from_user)(void *dst, void *src);
+	int (*compat_to_user)(void __user *dst, void *src);
 
 	/* Set this to THIS_MODULE if you are a module, otherwise NULL */
 	struct module *me;
@@ -186,6 +181,7 @@ struct xt_match
 
 	char *table;
 	unsigned int matchsize;
+	unsigned int compatsize;
 	unsigned int hooks;
 	unsigned short proto;
 
@@ -224,13 +220,15 @@ struct xt_target
 	void (*destroy)(const struct xt_target *target, void *targinfo);
 
 	/* Called when userspace align differs from kernel space one */
-	int (*compat)(void *target, void **dstptr, int *size, int convert);
+	void (*compat_from_user)(void *dst, void *src);
+	int (*compat_to_user)(void __user *dst, void *src);
 
 	/* Set this to THIS_MODULE if you are a module, otherwise NULL */
 	struct module *me;
 
 	char *table;
 	unsigned int targetsize;
+	unsigned int compatsize;
 	unsigned int hooks;
 	unsigned short proto;
 
@@ -387,9 +385,18 @@ struct compat_xt_counters_info
 
 extern void xt_compat_lock(int af);
 extern void xt_compat_unlock(int af);
-extern int xt_compat_match(void *match, void **dstptr, int *size, int convert);
-extern int xt_compat_target(void *target, void **dstptr, int *size,
-		int convert);
+
+extern int xt_compat_match_offset(struct xt_match *match);
+extern void xt_compat_match_from_user(struct xt_entry_match *m,
+				      void **dstptr, int *size);
+extern int xt_compat_match_to_user(struct xt_entry_match *m,
+				   void * __user *dstptr, int *size);
+
+extern int xt_compat_target_offset(struct xt_target *target);
+extern void xt_compat_target_from_user(struct xt_entry_target *t,
+				       void **dstptr, int *size);
+extern int xt_compat_target_to_user(struct xt_entry_target *t,
+				    void * __user *dstptr, int *size);
 
 #endif /* CONFIG_COMPAT */
 #endif /* __KERNEL__ */
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 673581db986..800067d69a9 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -942,73 +942,28 @@ static short compat_calc_jump(u_int16_t offset)
 	return delta;
 }
 
-struct compat_ipt_standard_target
+static void compat_standard_from_user(void *dst, void *src)
 {
-	struct compat_xt_entry_target target;
-	compat_int_t verdict;
-};
-
-struct compat_ipt_standard
-{
-	struct compat_ipt_entry entry;
-	struct compat_ipt_standard_target target;
-};
+	int v = *(compat_int_t *)src;
 
-#define IPT_ST_LEN		XT_ALIGN(sizeof(struct ipt_standard_target))
-#define IPT_ST_COMPAT_LEN	COMPAT_XT_ALIGN(sizeof(struct compat_ipt_standard_target))
-#define IPT_ST_OFFSET		(IPT_ST_LEN - IPT_ST_COMPAT_LEN)
+	if (v > 0)
+		v += compat_calc_jump(v);
+	memcpy(dst, &v, sizeof(v));
+}
 
-static int compat_ipt_standard_fn(void *target,
-		void **dstptr, int *size, int convert)
+static int compat_standard_to_user(void __user *dst, void *src)
 {
-	struct compat_ipt_standard_target compat_st, *pcompat_st;
-	struct ipt_standard_target st, *pst;
-	int ret;
+	compat_int_t cv = *(int *)src;
 
-	ret = 0;
-	switch (convert) {
-		case COMPAT_TO_USER:
-			pst = target;
-			memcpy(&compat_st.target, &pst->target,
-				sizeof(compat_st.target));
-			compat_st.verdict = pst->verdict;
-			if (compat_st.verdict > 0)
-				compat_st.verdict -=
-					compat_calc_jump(compat_st.verdict);
-			compat_st.target.u.user.target_size = IPT_ST_COMPAT_LEN;
-			if (copy_to_user(*dstptr, &compat_st, IPT_ST_COMPAT_LEN))
-				ret = -EFAULT;
-			*size -= IPT_ST_OFFSET;
-			*dstptr += IPT_ST_COMPAT_LEN;
-			break;
-		case COMPAT_FROM_USER:
-			pcompat_st = target;
-			memcpy(&st.target, &pcompat_st->target, IPT_ST_COMPAT_LEN);
-			st.verdict = pcompat_st->verdict;
-			if (st.verdict > 0)
-				st.verdict += compat_calc_jump(st.verdict);
-			st.target.u.user.target_size = IPT_ST_LEN;
-			memcpy(*dstptr, &st, IPT_ST_LEN);
-			*size += IPT_ST_OFFSET;
-			*dstptr += IPT_ST_LEN;
-			break;
-		case COMPAT_CALC_SIZE:
-			*size += IPT_ST_OFFSET;
-			break;
-		default:
-			ret = -ENOPROTOOPT;
-			break;
-	}
-	return ret;
+	if (cv > 0)
+		cv -= compat_calc_jump(cv);
+	return copy_to_user(dst, &cv, sizeof(cv)) ? -EFAULT : 0;
 }
 
 static inline int
 compat_calc_match(struct ipt_entry_match *m, int * size)
 {
-	if (m->u.kernel.match->compat)
-		m->u.kernel.match->compat(m, NULL, size, COMPAT_CALC_SIZE);
-	else
-		xt_compat_match(m, NULL, size, COMPAT_CALC_SIZE);
+	*size += xt_compat_match_offset(m->u.kernel.match);
 	return 0;
 }
 
@@ -1023,10 +978,7 @@ static int compat_calc_entry(struct ipt_entry *e, struct xt_table_info *info,
 	entry_offset = (void *)e - base;
 	IPT_MATCH_ITERATE(e, compat_calc_match, &off);
 	t = ipt_get_target(e);
-	if (t->u.kernel.target->compat)
-		t->u.kernel.target->compat(t, NULL, &off, COMPAT_CALC_SIZE);
-	else
-		xt_compat_target(t, NULL, &off, COMPAT_CALC_SIZE);
+	off += xt_compat_target_offset(t->u.kernel.target);
 	newinfo->size -= off;
 	ret = compat_add_offset(entry_offset, off);
 	if (ret)
@@ -1412,17 +1364,13 @@ struct compat_ipt_replace {
 };
 
 static inline int compat_copy_match_to_user(struct ipt_entry_match *m,
-		void __user **dstptr, compat_uint_t *size)
+		void * __user *dstptr, compat_uint_t *size)
 {
-	if (m->u.kernel.match->compat)
-		return m->u.kernel.match->compat(m, dstptr, size,
-				COMPAT_TO_USER);
-	else
-		return xt_compat_match(m, dstptr, size, COMPAT_TO_USER);
+	return xt_compat_match_to_user(m, dstptr, size);
 }
 
 static int compat_copy_entry_to_user(struct ipt_entry *e,
-		void __user **dstptr, compat_uint_t *size)
+		void * __user *dstptr, compat_uint_t *size)
 {
 	struct ipt_entry_target __user *t;
 	struct compat_ipt_entry __user *ce;
@@ -1442,11 +1390,7 @@ static int compat_copy_entry_to_user(struct ipt_entry *e,
 	if (ret)
 		goto out;
 	t = ipt_get_target(e);
-	if (t->u.kernel.target->compat)
-		ret = t->u.kernel.target->compat(t, dstptr, size,
-				COMPAT_TO_USER);
-	else
-		ret = xt_compat_target(t, dstptr, size, COMPAT_TO_USER);
+	ret = xt_compat_target_to_user(t, dstptr, size);
 	if (ret)
 		goto out;
 	ret = -EFAULT;
@@ -1478,11 +1422,7 @@ compat_check_calc_match(struct ipt_entry_match *m,
 		return match ? PTR_ERR(match) : -ENOENT;
 	}
 	m->u.kernel.match = match;
-
-	if (m->u.kernel.match->compat)
-		m->u.kernel.match->compat(m, NULL, size, COMPAT_CALC_SIZE);
-	else
-		xt_compat_match(m, NULL, size, COMPAT_CALC_SIZE);
+	*size += xt_compat_match_offset(match);
 
 	(*i)++;
 	return 0;
@@ -1543,10 +1483,7 @@ check_compat_entry_size_and_hooks(struct ipt_entry *e,
 	}
 	t->u.kernel.target = target;
 
-	if (t->u.kernel.target->compat)
-		t->u.kernel.target->compat(t, NULL, &off, COMPAT_CALC_SIZE);
-	else
-		xt_compat_target(t, NULL, &off, COMPAT_CALC_SIZE);
+	off += xt_compat_target_offset(target);
 	*size += off;
 	ret = compat_add_offset(entry_offset, off);
 	if (ret)
@@ -1584,10 +1521,7 @@ static inline int compat_copy_match_from_user(struct ipt_entry_match *m,
 
 	dm = (struct ipt_entry_match *)*dstptr;
 	match = m->u.kernel.match;
-	if (match->compat)
-		match->compat(m, dstptr, size, COMPAT_FROM_USER);
-	else
-		xt_compat_match(m, dstptr, size, COMPAT_FROM_USER);
+	xt_compat_match_from_user(m, dstptr, size);
 
 	ret = xt_check_match(match, AF_INET, dm->u.match_size - sizeof(*dm),
 			     name, hookmask, ip->proto,
@@ -1635,10 +1569,7 @@ static int compat_copy_entry_from_user(struct ipt_entry *e, void **dstptr,
 	de->target_offset = e->target_offset - (origsize - *size);
 	t = ipt_get_target(e);
 	target = t->u.kernel.target;
-	if (target->compat)
-		target->compat(t, dstptr, size, COMPAT_FROM_USER);
-	else
-		xt_compat_target(t, dstptr, size, COMPAT_FROM_USER);
+	xt_compat_target_from_user(t, dstptr, size);
 
 	de->next_offset = e->next_offset - (origsize - *size);
 	for (h = 0; h < NF_IP_NUMHOOKS; h++) {
@@ -2205,7 +2136,9 @@ static struct ipt_target ipt_standard_target = {
 	.targetsize	= sizeof(int),
 	.family		= AF_INET,
 #ifdef CONFIG_COMPAT
-	.compat		= &compat_ipt_standard_fn,
+	.compatsize	= sizeof(compat_int_t),
+	.compat_from_user = compat_standard_from_user,
+	.compat_to_user	= compat_standard_to_user,
 #endif
 };
 
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index be7baf4f684..58522fc65d3 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -333,52 +333,65 @@ int xt_check_match(const struct xt_match *match, unsigned short family,
 EXPORT_SYMBOL_GPL(xt_check_match);
 
 #ifdef CONFIG_COMPAT
-int xt_compat_match(void *match, void **dstptr, int *size, int convert)
+int xt_compat_match_offset(struct xt_match *match)
 {
-	struct xt_match *m;
-	struct compat_xt_entry_match *pcompat_m;
-	struct xt_entry_match *pm;
-	u_int16_t msize;
-	int off, ret;
+	u_int16_t csize = match->compatsize ? : match->matchsize;
+	return XT_ALIGN(match->matchsize) - COMPAT_XT_ALIGN(csize);
+}
+EXPORT_SYMBOL_GPL(xt_compat_match_offset);
 
-	ret = 0;
-	m = ((struct xt_entry_match *)match)->u.kernel.match;
-	off = XT_ALIGN(m->matchsize) - COMPAT_XT_ALIGN(m->matchsize);
-	switch (convert) {
-		case COMPAT_TO_USER:
-			pm = (struct xt_entry_match *)match;
-			msize = pm->u.user.match_size;
-			if (copy_to_user(*dstptr, pm, msize)) {
-				ret = -EFAULT;
-				break;
-			}
-			msize -= off;
-			if (put_user(msize, (u_int16_t *)*dstptr))
-				ret = -EFAULT;
-			*size -= off;
-			*dstptr += msize;
-			break;
-		case COMPAT_FROM_USER:
-			pcompat_m = (struct compat_xt_entry_match *)match;
-			pm = (struct xt_entry_match *)*dstptr;
-			msize = pcompat_m->u.user.match_size;
-			memcpy(pm, pcompat_m, msize);
-			msize += off;
-			pm->u.user.match_size = msize;
-			*size += off;
-			*dstptr += msize;
-			break;
-		case COMPAT_CALC_SIZE:
-			*size += off;
-			break;
-		default:
-			ret = -ENOPROTOOPT;
-			break;
+void xt_compat_match_from_user(struct xt_entry_match *m, void **dstptr,
+			       int *size)
+{
+	struct xt_match *match = m->u.kernel.match;
+	struct compat_xt_entry_match *cm = (struct compat_xt_entry_match *)m;
+	int pad, off = xt_compat_match_offset(match);
+	u_int16_t msize = cm->u.user.match_size;
+
+	m = *dstptr;
+	memcpy(m, cm, sizeof(*cm));
+	if (match->compat_from_user)
+		match->compat_from_user(m->data, cm->data);
+	else
+		memcpy(m->data, cm->data, msize - sizeof(*cm));
+	pad = XT_ALIGN(match->matchsize) - match->matchsize;
+	if (pad > 0)
+		memset(m->data + match->matchsize, 0, pad);
+
+	msize += off;
+	m->u.user.match_size = msize;
+
+	*size += off;
+	*dstptr += msize;
+}
+EXPORT_SYMBOL_GPL(xt_compat_match_from_user);
+
+int xt_compat_match_to_user(struct xt_entry_match *m, void __user **dstptr,
+			    int *size)
+{
+	struct xt_match *match = m->u.kernel.match;
+	struct compat_xt_entry_match __user *cm = *dstptr;
+	int off = xt_compat_match_offset(match);
+	u_int16_t msize = m->u.user.match_size - off;
+
+	if (copy_to_user(cm, m, sizeof(*cm)) ||
+	    put_user(msize, &cm->u.user.match_size))
+	    	return -EFAULT;
+
+	if (match->compat_to_user) {
+		if (match->compat_to_user((void __user *)cm->data, m->data))
+			return -EFAULT;
+	} else {
+		if (copy_to_user(cm->data, m->data, msize - sizeof(*cm)))
+			return -EFAULT;
 	}
-	return ret;
+
+	*size -= off;
+	*dstptr += msize;
+	return 0;
 }
-EXPORT_SYMBOL_GPL(xt_compat_match);
-#endif
+EXPORT_SYMBOL_GPL(xt_compat_match_to_user);
+#endif /* CONFIG_COMPAT */
 
 int xt_check_target(const struct xt_target *target, unsigned short family,
 		    unsigned int size, const char *table, unsigned int hook_mask,
@@ -410,51 +423,64 @@ int xt_check_target(const struct xt_target *target, unsigned short family,
 EXPORT_SYMBOL_GPL(xt_check_target);
 
 #ifdef CONFIG_COMPAT
-int xt_compat_target(void *target, void **dstptr, int *size, int convert)
+int xt_compat_target_offset(struct xt_target *target)
 {
-	struct xt_target *t;
-	struct compat_xt_entry_target *pcompat;
-	struct xt_entry_target *pt;
-	u_int16_t tsize;
-	int off, ret;
+	u_int16_t csize = target->compatsize ? : target->targetsize;
+	return XT_ALIGN(target->targetsize) - COMPAT_XT_ALIGN(csize);
+}
+EXPORT_SYMBOL_GPL(xt_compat_target_offset);
 
-	ret = 0;
-	t = ((struct xt_entry_target *)target)->u.kernel.target;
-	off = XT_ALIGN(t->targetsize) - COMPAT_XT_ALIGN(t->targetsize);
-	switch (convert) {
-		case COMPAT_TO_USER:
-			pt = (struct xt_entry_target *)target;
-			tsize = pt->u.user.target_size;
-			if (copy_to_user(*dstptr, pt, tsize)) {
-				ret = -EFAULT;
-				break;
-			}
-			tsize -= off;
-			if (put_user(tsize, (u_int16_t *)*dstptr))
-				ret = -EFAULT;
-			*size -= off;
-			*dstptr += tsize;
-			break;
-		case COMPAT_FROM_USER:
-			pcompat = (struct compat_xt_entry_target *)target;
-			pt = (struct xt_entry_target *)*dstptr;
-			tsize = pcompat->u.user.target_size;
-			memcpy(pt, pcompat, tsize);
-			tsize += off;
-			pt->u.user.target_size = tsize;
-			*size += off;
-			*dstptr += tsize;
-			break;
-		case COMPAT_CALC_SIZE:
-			*size += off;
-			break;
-		default:
-			ret = -ENOPROTOOPT;
-			break;
+void xt_compat_target_from_user(struct xt_entry_target *t, void **dstptr,
+			        int *size)
+{
+	struct xt_target *target = t->u.kernel.target;
+	struct compat_xt_entry_target *ct = (struct compat_xt_entry_target *)t;
+	int pad, off = xt_compat_target_offset(target);
+	u_int16_t tsize = ct->u.user.target_size;
+
+	t = *dstptr;
+	memcpy(t, ct, sizeof(*ct));
+	if (target->compat_from_user)
+		target->compat_from_user(t->data, ct->data);
+	else
+		memcpy(t->data, ct->data, tsize - sizeof(*ct));
+	pad = XT_ALIGN(target->targetsize) - target->targetsize;
+	if (pad > 0)
+		memset(t->data + target->targetsize, 0, pad);
+
+	tsize += off;
+	t->u.user.target_size = tsize;
+
+	*size += off;
+	*dstptr += tsize;
+}
+EXPORT_SYMBOL_GPL(xt_compat_target_from_user);
+
+int xt_compat_target_to_user(struct xt_entry_target *t, void __user **dstptr,
+			     int *size)
+{
+	struct xt_target *target = t->u.kernel.target;
+	struct compat_xt_entry_target __user *ct = *dstptr;
+	int off = xt_compat_target_offset(target);
+	u_int16_t tsize = t->u.user.target_size - off;
+
+	if (copy_to_user(ct, t, sizeof(*ct)) ||
+	    put_user(tsize, &ct->u.user.target_size))
+	    	return -EFAULT;
+
+	if (target->compat_to_user) {
+		if (target->compat_to_user((void __user *)ct->data, t->data))
+			return -EFAULT;
+	} else {
+		if (copy_to_user(ct->data, t->data, tsize - sizeof(*ct)))
+			return -EFAULT;
 	}
-	return ret;
+
+	*size -= off;
+	*dstptr += tsize;
+	return 0;
 }
-EXPORT_SYMBOL_GPL(xt_compat_target);
+EXPORT_SYMBOL_GPL(xt_compat_target_to_user);
 #endif
 
 struct xt_table_info *xt_alloc_table_info(unsigned int size)