Commit ba47396e authored by Maciej Żenczykowski's avatar Maciej Żenczykowski Committed by Daniel Borkmann
Browse files

Revert "bpf: Check for BPF_F_ADJ_ROOM_FIXED_GSO when bpf_skb_change_proto" 



This reverts commit fa7b83bf.

See the followup commit for the reasoning why I believe the appropriate
approach is to simply make this change without a flag, but it can basically
be summarized as using this helper without the flag is bug-prone or outright
buggy, and thus the default should be this new behaviour.

As this commit has only made it into net-next/master, but not into
any real release, such a backwards incompatible change is still ok.

Signed-off-by: default avatarMaciej Żenczykowski <maze@google.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Cc: Dongseok Yi <dseok.yi@samsung.com>
Cc: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/bpf/20210617000953.2787453-1-zenczykowski@gmail.com
parent 647d446d

net/core/filter.c

+9 −13
Original line number Diff line number Diff line
@@ -3235,7 +3235,7 @@ static int bpf_skb_net_hdr_pop(struct sk_buff *skb, u32 off, u32 len) 
	return ret;

}



static int bpf_skb_proto_4_to_6(struct sk_buff *skb, u64 flags)

static int bpf_skb_proto_4_to_6(struct sk_buff *skb)

{

	const u32 len_diff = sizeof(struct ipv6hdr) - sizeof(struct iphdr);

	u32 off = skb_mac_header_len(skb);
@@ -3264,9 +3264,7 @@ static int bpf_skb_proto_4_to_6(struct sk_buff *skb, u64 flags) 
		}



		/* Due to IPv6 header, MSS needs to be downgraded. */

		if (!(flags & BPF_F_ADJ_ROOM_FIXED_GSO))

		skb_decrease_gso_size(shinfo, len_diff);



		/* Header must be checked, and gso_segs recomputed. */

		shinfo->gso_type |= SKB_GSO_DODGY;

		shinfo->gso_segs = 0;
@@ -3278,7 +3276,7 @@ static int bpf_skb_proto_4_to_6(struct sk_buff *skb, u64 flags) 
	return 0;

}



static int bpf_skb_proto_6_to_4(struct sk_buff *skb, u64 flags)

static int bpf_skb_proto_6_to_4(struct sk_buff *skb)

{

	const u32 len_diff = sizeof(struct ipv6hdr) - sizeof(struct iphdr);

	u32 off = skb_mac_header_len(skb);
@@ -3307,9 +3305,7 @@ static int bpf_skb_proto_6_to_4(struct sk_buff *skb, u64 flags) 
		}



		/* Due to IPv4 header, MSS can be upgraded. */

		if (!(flags & BPF_F_ADJ_ROOM_FIXED_GSO))

		skb_increase_gso_size(shinfo, len_diff);



		/* Header must be checked, and gso_segs recomputed. */

		shinfo->gso_type |= SKB_GSO_DODGY;

		shinfo->gso_segs = 0;
@@ -3321,17 +3317,17 @@ static int bpf_skb_proto_6_to_4(struct sk_buff *skb, u64 flags) 
	return 0;

}



static int bpf_skb_proto_xlat(struct sk_buff *skb, __be16 to_proto, u64 flags)

static int bpf_skb_proto_xlat(struct sk_buff *skb, __be16 to_proto)

{

	__be16 from_proto = skb->protocol;



	if (from_proto == htons(ETH_P_IP) &&

	      to_proto == htons(ETH_P_IPV6))

		return bpf_skb_proto_4_to_6(skb, flags);

		return bpf_skb_proto_4_to_6(skb);



	if (from_proto == htons(ETH_P_IPV6) &&

	      to_proto == htons(ETH_P_IP))

		return bpf_skb_proto_6_to_4(skb, flags);

		return bpf_skb_proto_6_to_4(skb);



	return -ENOTSUPP;

}
@@ -3341,7 +3337,7 @@ BPF_CALL_3(bpf_skb_change_proto, struct sk_buff *, skb, __be16, proto, 
{

	int ret;



	if (unlikely(flags & ~(BPF_F_ADJ_ROOM_FIXED_GSO)))

	if (unlikely(flags))

		return -EINVAL;



	/* General idea is that this helper does the basic groundwork
@@ -3361,7 +3357,7 @@ BPF_CALL_3(bpf_skb_change_proto, struct sk_buff *, skb, __be16, proto, 
	 * that. For offloads, we mark packet as dodgy, so that headers

	 * need to be verified first.

	 */

	ret = bpf_skb_proto_xlat(skb, proto, flags);

	ret = bpf_skb_proto_xlat(skb, proto);

	bpf_compute_data_pointers(skb);

	return ret;

}