[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>

1 files changed, 109 insertions, 83 deletions

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index be7baf4f6846..58522fc65d33 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)