tcp_gso_segment check for the size of GROed payload if it is bigger than the mss. bpf_skb_proto_6_to_4 increases mss, but the mss can be bigger than the size of GROed payload unexpectedly if data_len is not big enough. Assume that skb gso_size = 1372 and data_len = 8. bpf_skb_proto_6_to_4 would increse the gso_size to 1392. tcp_gso_segment will get an error with 1380 <= 1392. Check for the size of GROed payload if it is really bigger than target mss when increase mss. Fixes: 6578171a7ff0 (bpf: add bpf_skb_change_proto helper) Signed-off-by: Dongseok Yi <dseok.yi@xxxxxxxxxxx> --- net/core/filter.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/core/filter.c b/net/core/filter.c index 9323d34..3f79e3c 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -3308,7 +3308,9 @@ 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 (skb->data_len > len_diff) + 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; -- 2.7.4
