Commit b90efd22 authored by Willem de Bruijn's avatar Willem de Bruijn Committed by Alexei Starovoitov
Browse files

bpf: only adjust gso_size on bytestream protocols 



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 d02f51cb ("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: bec1f6f6 ("udp: generate gso with UDP_SEGMENT")
Signed-off-by: default avatarWillem de Bruijn <willemb@google.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent d6238766

include/linux/skbuff.h

+6 −0
Original line number Diff line number Diff line
@@ -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;

net/core/filter.c

+4 −8
Original line number Diff line number Diff line
@@ -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);

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