netfilter: x_tables: introduce and use xt_copy_counters_from_user

The three variants use same copy&pasted code, condense this into a
helper and use that.

Make sure info.name is 0-terminated.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

5 files changed, 92 insertions, 130 deletions

diff --git a/include/linux/netfilter/x_tables.h b/include/linux/netfilter/x_tables.h
index e2da9b90f1b8..4dd9306c9d56 100644
--- a/include/linux/netfilter/x_tables.h
+++ b/include/linux/netfilter/x_tables.h
@@ -251,6 +251,9 @@ int xt_check_match(struct xt_mtchk_param *, unsigned int size, u_int8_t proto,
 int xt_check_target(struct xt_tgchk_param *, unsigned int size, u_int8_t proto,
                     bool inv_proto);
 
+void *xt_copy_counters_from_user(const void __user *user, unsigned int len,
+                                 struct xt_counters_info *info, bool compat);
+
 struct xt_table *xt_register_table(struct net *net,
                                    const struct xt_table *table,
                                    struct xt_table_info *bootstrap,
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 8cefb7a2606b..60f5161abcb4 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -1123,55 +1123,17 @@ static int do_add_counters(struct net *net, const void __user *user,
         unsigned int i;
         struct xt_counters_info tmp;
         struct xt_counters *paddc;
-        unsigned int num_counters;
-        const char *name;
-        int size;
-        void *ptmp;
         struct xt_table *t;
         const struct xt_table_info *private;
         int ret = 0;
         struct arpt_entry *iter;
         unsigned int addend;
-#ifdef CONFIG_COMPAT
-        struct compat_xt_counters_info compat_tmp;
-
-        if (compat) {
-                ptmp = &compat_tmp;
-                size = sizeof(struct compat_xt_counters_info);
-        } else
-#endif
-        {
-                ptmp = &tmp;
-                size = sizeof(struct xt_counters_info);
-        }
 
-        if (copy_from_user(ptmp, user, size) != 0)
-                return -EFAULT;
-
-#ifdef CONFIG_COMPAT
-        if (compat) {
-                num_counters = compat_tmp.num_counters;
-                name = compat_tmp.name;
-        } else
-#endif
-        {
-                num_counters = tmp.num_counters;
-                name = tmp.name;
-        }
-
-        if (len != size + num_counters * sizeof(struct xt_counters))
-                return -EINVAL;
-
-        paddc = vmalloc(len - size);
-        if (!paddc)
-                return -ENOMEM;
-
-        if (copy_from_user(paddc, user + size, len - size) != 0) {
-                ret = -EFAULT;
-                goto free;
-        }
+        paddc = xt_copy_counters_from_user(user, len, &tmp, compat);
+        if (IS_ERR(paddc))
+                return PTR_ERR(paddc);
 
-        t = xt_find_table_lock(net, NFPROTO_ARP, name);
+        t = xt_find_table_lock(net, NFPROTO_ARP, tmp.name);
         if (IS_ERR_OR_NULL(t)) {
                 ret = t ? PTR_ERR(t) : -ENOENT;
                 goto free;
@@ -1179,7 +1141,7 @@ static int do_add_counters(struct net *net, const void __user *user,
 
         local_bh_disable();
         private = t->private;
-        if (private->number != num_counters) {
+        if (private->number != tmp.num_counters) {
                 ret = -EINVAL;
                 goto unlock_up_free;
         }
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 9340ce0a7549..735d1ee8c1ab 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -1307,55 +1307,17 @@ do_add_counters(struct net *net, const void __user *user,
         unsigned int i;
         struct xt_counters_info tmp;
         struct xt_counters *paddc;
-        unsigned int num_counters;
-        const char *name;
-        int size;
-        void *ptmp;
         struct xt_table *t;
         const struct xt_table_info *private;
         int ret = 0;
         struct ipt_entry *iter;
         unsigned int addend;
-#ifdef CONFIG_COMPAT
-        struct compat_xt_counters_info compat_tmp;
-
-        if (compat) {
-                ptmp = &compat_tmp;
-                size = sizeof(struct compat_xt_counters_info);
-        } else
-#endif
-        {
-                ptmp = &tmp;
-                size = sizeof(struct xt_counters_info);
-        }
 
-        if (copy_from_user(ptmp, user, size) != 0)
-                return -EFAULT;
-
-#ifdef CONFIG_COMPAT
-        if (compat) {
-                num_counters = compat_tmp.num_counters;
-                name = compat_tmp.name;
-        } else
-#endif
-        {
-                num_counters = tmp.num_counters;
-                name = tmp.name;
-        }
-
-        if (len != size + num_counters * sizeof(struct xt_counters))
-                return -EINVAL;
-
-        paddc = vmalloc(len - size);
-        if (!paddc)
-                return -ENOMEM;
-
-        if (copy_from_user(paddc, user + size, len - size) != 0) {
-                ret = -EFAULT;
-                goto free;
-        }
+        paddc = xt_copy_counters_from_user(user, len, &tmp, compat);
+        if (IS_ERR(paddc))
+                return PTR_ERR(paddc);
 
-        t = xt_find_table_lock(net, AF_INET, name);
+        t = xt_find_table_lock(net, AF_INET, tmp.name);
         if (IS_ERR_OR_NULL(t)) {
                 ret = t ? PTR_ERR(t) : -ENOENT;
                 goto free;
@@ -1363,7 +1325,7 @@ do_add_counters(struct net *net, const void __user *user,
 
         local_bh_disable();
         private = t->private;
-        if (private->number != num_counters) {
+        if (private->number != tmp.num_counters) {
                 ret = -EINVAL;
                 goto unlock_up_free;
         }
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index aa010856a255..73e606c719ef 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -1319,55 +1319,16 @@ do_add_counters(struct net *net, const void __user *user, unsigned int len,
         unsigned int i;
         struct xt_counters_info tmp;
         struct xt_counters *paddc;
-        unsigned int num_counters;
-        char *name;
-        int size;
-        void *ptmp;
         struct xt_table *t;
         const struct xt_table_info *private;
         int ret = 0;
         struct ip6t_entry *iter;
         unsigned int addend;
-#ifdef CONFIG_COMPAT
-        struct compat_xt_counters_info compat_tmp;
-
-        if (compat) {
-                ptmp = &compat_tmp;
-                size = sizeof(struct compat_xt_counters_info);
-        } else
-#endif
-        {
-                ptmp = &tmp;
-                size = sizeof(struct xt_counters_info);
-        }
-
-        if (copy_from_user(ptmp, user, size) != 0)
-                return -EFAULT;
-
-#ifdef CONFIG_COMPAT
-        if (compat) {
-                num_counters = compat_tmp.num_counters;
-                name = compat_tmp.name;
-        } else
-#endif
-        {
-                num_counters = tmp.num_counters;
-                name = tmp.name;
-        }
-
-        if (len != size + num_counters * sizeof(struct xt_counters))
-                return -EINVAL;
-
-        paddc = vmalloc(len - size);
-        if (!paddc)
-                return -ENOMEM;
-
-        if (copy_from_user(paddc, user + size, len - size) != 0) {
-                ret = -EFAULT;
-                goto free;
-        }
 
-        t = xt_find_table_lock(net, AF_INET6, name);
+        paddc = xt_copy_counters_from_user(user, len, &tmp, compat);
+        if (IS_ERR(paddc))
+                return PTR_ERR(paddc);
+        t = xt_find_table_lock(net, AF_INET6, tmp.name);
         if (IS_ERR_OR_NULL(t)) {
                 ret = t ? PTR_ERR(t) : -ENOENT;
                 goto free;
@@ -1375,7 +1336,7 @@ do_add_counters(struct net *net, const void __user *user, unsigned int len,
 
         local_bh_disable();
         private = t->private;
-        if (private->number != num_counters) {
+        if (private->number != tmp.num_counters) {
                 ret = -EINVAL;
                 goto unlock_up_free;
         }
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 9ec23ffa43b4..c69c892231d7 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -752,6 +752,80 @@ int xt_check_target(struct xt_tgchk_param *par,
 }
 EXPORT_SYMBOL_GPL(xt_check_target);
 
+/**
+ * xt_copy_counters_from_user - copy counters and metadata from userspace
+ *
+ * @user: src pointer to userspace memory
+ * @len: alleged size of userspace memory
+ * @info: where to store the xt_counters_info metadata
+ * @compat: true if we setsockopt call is done by 32bit task on 64bit kernel
+ *
+ * Copies counter meta data from @user and stores it in @info.
+ *
+ * vmallocs memory to hold the counters, then copies the counter data
+ * from @user to the new memory and returns a pointer to it.
+ *
+ * If @compat is true, @info gets converted automatically to the 64bit
+ * representation.
+ *
+ * The metadata associated with the counters is stored in @info.
+ *
+ * Return: returns pointer that caller has to test via IS_ERR().
+ * If IS_ERR is false, caller has to vfree the pointer.
+ */
+void *xt_copy_counters_from_user(const void __user *user, unsigned int len,
+                                 struct xt_counters_info *info, bool compat)
+{
+        void *mem;
+        u64 size;
+
+#ifdef CONFIG_COMPAT
+        if (compat) {
+                /* structures only differ in size due to alignment */
+                struct compat_xt_counters_info compat_tmp;
+
+                if (len <= sizeof(compat_tmp))
+                        return ERR_PTR(-EINVAL);
+
+                len -= sizeof(compat_tmp);
+                if (copy_from_user(&compat_tmp, user, sizeof(compat_tmp)) != 0)
+                        return ERR_PTR(-EFAULT);
+
+                strlcpy(info->name, compat_tmp.name, sizeof(info->name));
+                info->num_counters = compat_tmp.num_counters;
+                user += sizeof(compat_tmp);
+        } else
+#endif
+        {
+                if (len <= sizeof(*info))
+                        return ERR_PTR(-EINVAL);
+
+                len -= sizeof(*info);
+                if (copy_from_user(info, user, sizeof(*info)) != 0)
+                        return ERR_PTR(-EFAULT);
+
+                info->name[sizeof(info->name) - 1] = '\0';
+                user += sizeof(*info);
+        }
+
+        size = sizeof(struct xt_counters);
+        size *= info->num_counters;
+
+        if (size != (u64)len)
+                return ERR_PTR(-EINVAL);
+
+        mem = vmalloc(len);
+        if (!mem)
+                return ERR_PTR(-ENOMEM);
+
+        if (copy_from_user(mem, user, len) == 0)
+                return mem;
+
+        vfree(mem);
+        return ERR_PTR(-EFAULT);
+}
+EXPORT_SYMBOL_GPL(xt_copy_counters_from_user);
+
 #ifdef CONFIG_COMPAT
 int xt_compat_target_offset(const struct xt_target *target)
 {