diff options
author | Dongseok Yi <dseok.yi@samsung.com> | 2021-05-12 16:27:33 +0900 |
---|---|---|
committer | Daniel Borkmann <daniel@iogearbox.net> | 2021-05-18 22:05:36 +0200 |
commit | fa7b83bf3b156c767f3e4a25bbf3817b08f3ff8e (patch) | |
tree | 7519c58ba4dbaf42da1cc19e069d405011bb72e7 | |
parent | c49661aa6f7097047b7e86ad37b1cf308a7a8d4f (diff) |
bpf: Check for BPF_F_ADJ_ROOM_FIXED_GSO when bpf_skb_change_proto
In the forwarding path GRO -> BPF 6 to 4 -> GSO for TCP traffic, the
coalesced packet payload can be > MSS, but < MSS + 20.
bpf_skb_proto_6_to_4() will upgrade the MSS and it can be > the payload
length. After then tcp_gso_segment checks for the payload length if it
is <= MSS. The condition is causing the packet to be dropped.
tcp_gso_segment():
[...]
mss = skb_shinfo(skb)->gso_size;
if (unlikely(skb->len <= mss))
goto out;
[...]
Allow to upgrade/downgrade MSS only when BPF_F_ADJ_ROOM_FIXED_GSO is
not set.
Signed-off-by: Dongseok Yi <dseok.yi@samsung.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/bpf/1620804453-57566-1-git-send-email-dseok.yi@samsung.com
-rw-r--r-- | net/core/filter.c | 22 |
1 files changed, 13 insertions, 9 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index cae56d08a670..582ac196fd94 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -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) +static int bpf_skb_proto_4_to_6(struct sk_buff *skb, u64 flags) { const u32 len_diff = sizeof(struct ipv6hdr) - sizeof(struct iphdr); u32 off = skb_mac_header_len(skb); @@ -3264,7 +3264,9 @@ static int bpf_skb_proto_4_to_6(struct sk_buff *skb) } /* Due to IPv6 header, MSS needs to be downgraded. */ - skb_decrease_gso_size(shinfo, len_diff); + 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; @@ -3276,7 +3278,7 @@ static int bpf_skb_proto_4_to_6(struct sk_buff *skb) return 0; } -static int bpf_skb_proto_6_to_4(struct sk_buff *skb) +static int bpf_skb_proto_6_to_4(struct sk_buff *skb, u64 flags) { const u32 len_diff = sizeof(struct ipv6hdr) - sizeof(struct iphdr); u32 off = skb_mac_header_len(skb); @@ -3305,7 +3307,9 @@ static int bpf_skb_proto_6_to_4(struct sk_buff *skb) } /* Due to IPv4 header, MSS can be upgraded. */ - skb_increase_gso_size(shinfo, len_diff); + 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; @@ -3317,17 +3321,17 @@ static int bpf_skb_proto_6_to_4(struct sk_buff *skb) return 0; } -static int bpf_skb_proto_xlat(struct sk_buff *skb, __be16 to_proto) +static int bpf_skb_proto_xlat(struct sk_buff *skb, __be16 to_proto, u64 flags) { __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); + return bpf_skb_proto_4_to_6(skb, flags); if (from_proto == htons(ETH_P_IPV6) && to_proto == htons(ETH_P_IP)) - return bpf_skb_proto_6_to_4(skb); + return bpf_skb_proto_6_to_4(skb, flags); return -ENOTSUPP; } @@ -3337,7 +3341,7 @@ BPF_CALL_3(bpf_skb_change_proto, struct sk_buff *, skb, __be16, proto, { int ret; - if (unlikely(flags)) + if (unlikely(flags & ~(BPF_F_ADJ_ROOM_FIXED_GSO))) return -EINVAL; /* General idea is that this helper does the basic groundwork @@ -3357,7 +3361,7 @@ 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); + ret = bpf_skb_proto_xlat(skb, proto, flags); bpf_compute_data_pointers(skb); return ret; } |