Merge branch 'bnx2x-disable-GSO-on-too-large-packets'

Daniel Axtens says:

====================
bnx2x: disable GSO on too-large packets

We observed a case where a packet received on an ibmveth device had a
GSO size of around 10kB. This was forwarded by Open vSwitch to a bnx2x
device, where it caused a firmware assert. This is described in detail
at [0].

Ultimately we want a fix in the core, but that is very tricky to
backport. So for now, just stop the bnx2x driver from crashing.

When net-next re-opens I will send the fix to the core and a revert
for this.

v4 changes:
  - fix compilation error with EXPORTs (patch 1)
  - only do slow test if gso_size is greater than 9000 bytes (patch 2)

Thanks,
Daniel

[0]: https://patchwork.ozlabs.org/patch/859410/
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c

@@ -12934,6 +12934,24 @@ static netdev_features_t bnx2x_features_check(struct sk_buff *skb,
 					      struct net_device *dev,
 					      netdev_features_t features)
 {
+	/*
+	 * A skb with gso_size + header length > 9700 will cause a
+	 * firmware panic. Drop GSO support.
+	 *
+	 * Eventually the upper layer should not pass these packets down.
+	 *
+	 * For speed, if the gso_size is <= 9000, assume there will
+	 * not be 700 bytes of headers and pass it through. Only do a
+	 * full (slow) validation if the gso_size is > 9000.
+	 *
+	 * (Due to the way SKB_BY_FRAGS works this will also do a full
+	 * validation in that case.)
+	 */
+	if (unlikely(skb_is_gso(skb) &&
+		     (skb_shinfo(skb)->gso_size > 9000) &&
+		     !skb_gso_validate_mac_len(skb, 9700)))
+		features &= ~NETIF_F_GSO_MASK;
+
 	features = vlan_features_check(skb, features);
 	return vxlan_features_check(skb, features);
 }

include/linux/skbuff.h

@@ -3287,6 +3287,7 @@ int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen);
 void skb_scrub_packet(struct sk_buff *skb, bool xnet);
 unsigned int skb_gso_transport_seglen(const struct sk_buff *skb);
 bool skb_gso_validate_mtu(const struct sk_buff *skb, unsigned int mtu);
+bool skb_gso_validate_mac_len(const struct sk_buff *skb, unsigned int len);
 struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features);
 struct sk_buff *skb_vlan_untag(struct sk_buff *skb);
 int skb_ensure_writable(struct sk_buff *skb, int write_len);
@@ -4120,6 +4121,21 @@ static inline unsigned int skb_gso_network_seglen(const struct sk_buff *skb)
 	return hdr_len + skb_gso_transport_seglen(skb);
 }
 
+/**
+ * skb_gso_mac_seglen - Return length of individual segments of a gso packet
+ *
+ * @skb: GSO skb
+ *
+ * skb_gso_mac_seglen is used to determine the real size of the
+ * individual segments, including MAC/L2, Layer3 (IP, IPv6) and L4
+ * headers (TCP/UDP).
+ */
+static inline unsigned int skb_gso_mac_seglen(const struct sk_buff *skb)
+{
+	unsigned int hdr_len = skb_transport_header(skb) - skb_mac_header(skb);
+	return hdr_len + skb_gso_transport_seglen(skb);
+}
+
 /* Local Checksum Offload.
  * Compute outer checksum based on the assumption that the
  * inner checksum will be offloaded later.

net/core/skbuff.c

@@ -4913,6 +4913,45 @@ 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
  *
@@ -4924,27 +4963,25 @@ 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)
 {
 	if (skb_cow(skb, skb_headroom(skb)) < 0) {

net/sched/sch_tbf.c

@@ -142,16 +142,6 @@ static u64 psched_ns_t2l(const struct psched_ratecfg *r,
 	return len;
 }
 
-/*
- * Return length of individual segments of a gso packet,
- * including all headers (MAC, IP, TCP/UDP)
- */
-static unsigned int skb_gso_mac_seglen(const struct sk_buff *skb)
-{
-	unsigned int hdr_len = skb_transport_header(skb) - skb_mac_header(skb);
-	return hdr_len + skb_gso_transport_seglen(skb);
-}
-
 /* GSO packet is too big, segment it so that tbf can transmit
  * each segment in time
  */