net: create skb_gso_validate_mac_len()
commit 2b16f048729bf35e6c28a40cbfad07239f9dcd90 upstream
If you take a GSO skb, and split it into packets, will the MAC
length (L2 + L3 + L4 headers + payload) of those packets be small
enough to fit within a given length?
Move skb_gso_mac_seglen() to skbuff.h with other related functions
like skb_gso_network_seglen() so we can use it, and then create
skb_gso_validate_mac_len to do the full calculation.
Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
[jwang: cherry pick for CVE-2018-1000026]
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index dca1fed..1150116 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4469,6 +4469,45 @@ unsigned int skb_gso_transport_seglen(const struct sk_buff *skb)
EXPORT_SYMBOL_GPL(skb_gso_transport_seglen);
/**
+ * skb_gso_size_check - check the skb size, considering GSO_BY_FRAGS
+ *
+ * There are a couple of instances where we have a GSO skb, and we
+ * want to determine what size it would be after it is segmented.
+ *
+ * We might want to check:
+ * - L3+L4+payload size (e.g. IP forwarding)
+ * - L2+L3+L4+payload size (e.g. sanity check before passing to driver)
+ *
+ * This is a helper to do that correctly considering GSO_BY_FRAGS.
+ *
+ * @seg_len: The segmented length (from skb_gso_*_seglen). In the
+ * GSO_BY_FRAGS case this will be [header sizes + GSO_BY_FRAGS].
+ *
+ * @max_len: The maximum permissible length.
+ *
+ * Returns true if the segmented length <= max length.
+ */
+static inline bool skb_gso_size_check(const struct sk_buff *skb,
+ unsigned int seg_len,
+ unsigned int max_len) {
+ const struct skb_shared_info *shinfo = skb_shinfo(skb);
+ const struct sk_buff *iter;
+
+ if (shinfo->gso_size != GSO_BY_FRAGS)
+ return seg_len <= max_len;
+
+ /* Undo this so we can re-use header sizes */
+ seg_len -= GSO_BY_FRAGS;
+
+ skb_walk_frags(skb, iter) {
+ if (seg_len + skb_headlen(iter) > max_len)
+ return false;
+ }
+
+ return true;
+}
+
+/**
* skb_gso_validate_mtu - Return in case such skb fits a given MTU
*
* @skb: GSO skb
@@ -4479,27 +4518,25 @@ EXPORT_SYMBOL_GPL(skb_gso_transport_seglen);
*/
bool skb_gso_validate_mtu(const struct sk_buff *skb, unsigned int mtu)
{
- const struct skb_shared_info *shinfo = skb_shinfo(skb);
- const struct sk_buff *iter;
- unsigned int hlen;
-
- hlen = skb_gso_network_seglen(skb);
-
- if (shinfo->gso_size != GSO_BY_FRAGS)
- return hlen <= mtu;
-
- /* Undo this so we can re-use header sizes */
- hlen -= GSO_BY_FRAGS;
-
- skb_walk_frags(skb, iter) {
- if (hlen + skb_headlen(iter) > mtu)
- return false;
- }
-
- return true;
+ return skb_gso_size_check(skb, skb_gso_network_seglen(skb), mtu);
}
EXPORT_SYMBOL_GPL(skb_gso_validate_mtu);
+/**
+ * skb_gso_validate_mac_len - Will a split GSO skb fit in a given length?
+ *
+ * @skb: GSO skb
+ * @len: length to validate against
+ *
+ * skb_gso_validate_mac_len validates if a given skb will fit a wanted
+ * length once split, including L2, L3 and L4 headers and the payload.
+ */
+bool skb_gso_validate_mac_len(const struct sk_buff *skb, unsigned int len)
+{
+ return skb_gso_size_check(skb, skb_gso_mac_seglen(skb), len);
+}
+EXPORT_SYMBOL_GPL(skb_gso_validate_mac_len);
+
static struct sk_buff *skb_reorder_vlan_header(struct sk_buff *skb)
{
int mac_len;