bpf: only adjust gso_size on bytestream protocols

wdebruij · Alexei Starovoitov · commit b90efd225874 · 2019-02-10T19:57:34.000-08:00
bpf_skb_change_proto and bpf_skb_adjust_room change skb header length. For GSO packets they adjust gso_size to maintain the same MTU. The gso size can only be safely adjusted on bytestream protocols. Commit d02f51c ("bpf: fix bpf_skb_adjust_net/bpf_skb_proto_xlat to deal with gso sctp skbs") excluded SKB_GSO_SCTP. Since then type SKB_GSO_UDP_L4 has been added, whose contents are one gso_size unit per datagram. Also exclude these. Move from a blacklist to a whitelist check to future proof against additional such new GSO types, e.g., for fraglist based GRO. Fixes: bec1f6f ("udp: generate gso with UDP_SEGMENT") Signed-off-by: Willem de Bruijn <willemb@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
@@ -4212,6 +4212,12 @@ static inline bool skb_is_gso_sctp(const struct sk_buff *skb)
 	return skb_shinfo(skb)->gso_type & SKB_GSO_SCTP;
 }
 
+static inline bool skb_is_gso_tcp(const struct sk_buff *skb)
+{
+	return skb_is_gso(skb) &&
+	       skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6);
+}
+
 static inline void skb_gso_reset(struct sk_buff *skb)
 {
 	skb_shinfo(skb)->gso_size = 0;
diff --git a/net/core/filter.c b/net/core/filter.c
@@ -2789,8 +2789,7 @@ static int bpf_skb_proto_4_to_6(struct sk_buff *skb)
 	u32 off = skb_mac_header_len(skb);
 	int ret;
 
-	/* SCTP uses GSO_BY_FRAGS, thus cannot adjust it. */
-	if (skb_is_gso(skb) && unlikely(skb_is_gso_sctp(skb)))
+	if (!skb_is_gso_tcp(skb))
 		return -ENOTSUPP;
 
 	ret = skb_cow(skb, len_diff);
@@ -2831,8 +2830,7 @@ static int bpf_skb_proto_6_to_4(struct sk_buff *skb)
 	u32 off = skb_mac_header_len(skb);
 	int ret;
 
-	/* SCTP uses GSO_BY_FRAGS, thus cannot adjust it. */
-	if (skb_is_gso(skb) && unlikely(skb_is_gso_sctp(skb)))
+	if (!skb_is_gso_tcp(skb))
 		return -ENOTSUPP;
 
 	ret = skb_unclone(skb, GFP_ATOMIC);
@@ -2957,8 +2955,7 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 len_diff)
 	u32 off = skb_mac_header_len(skb) + bpf_skb_net_base_len(skb);
 	int ret;
 
-	/* SCTP uses GSO_BY_FRAGS, thus cannot adjust it. */
-	if (skb_is_gso(skb) && unlikely(skb_is_gso_sctp(skb)))
+	if (!skb_is_gso_tcp(skb))
 		return -ENOTSUPP;
 
 	ret = skb_cow(skb, len_diff);
@@ -2987,8 +2984,7 @@ static int bpf_skb_net_shrink(struct sk_buff *skb, u32 len_diff)
 	u32 off = skb_mac_header_len(skb) + bpf_skb_net_base_len(skb);
 	int ret;
 
-	/* SCTP uses GSO_BY_FRAGS, thus cannot adjust it. */
-	if (skb_is_gso(skb) && unlikely(skb_is_gso_sctp(skb)))
+	if (!skb_is_gso_tcp(skb))
 		return -ENOTSUPP;
 
 	ret = skb_unclone(skb, GFP_ATOMIC);

Original file line number	Diff line number	Diff line change
`@@ -4212,6 +4212,12 @@ static inline bool skb_is_gso_sctp(const struct sk_buff *skb)`
`4212`	`4212`	`return skb_shinfo(skb)->gso_type & SKB_GSO_SCTP;`
`4213`	`4213`	`}`
`4214`	`4214`
	`4215`	`+static inline bool skb_is_gso_tcp(const struct sk_buff *skb)`
	`4216`	`+{`
	`4217`	`+ return skb_is_gso(skb) &&`
	`4218`	`+ skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 \| SKB_GSO_TCPV6);`
	`4219`	`+}`
	`4220`	`+`
`4215`	`4221`	`static inline void skb_gso_reset(struct sk_buff *skb)`
`4216`	`4222`	`{`
`4217`	`4223`	`skb_shinfo(skb)->gso_size = 0;`