[PATCH v4] bpf: Fixed a segment issue when downgrade gso_size
From: Fred Li <hidden>
Date: 2024-07-19 02:47:03
Also in:
bpf, lkml
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [networking] (tcx & tc bpf, sock_addr), networking [general], the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Linearizing skb when downgrade gso_size because it may trigger the BUG_ON when segment skb as described in [1]. v4 changes: add fixed tag. v3 changes: linearize skb if having frag_list as Willem de Bruijn suggested[2]. [1] https://lore.kernel.org/all/20240626065555.35460-2-dracodingfly@gmail.com/ (local) [2] https://lore.kernel.org/all/668d5cf1ec330_1c18c32947@willemb.c.googlers.com.notmuch/ (local) Fixes: 2be7e212d5419 ("bpf: add bpf_skb_adjust_room helper") Signed-off-by: Fred Li <redacted> --- net/core/filter.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index df4578219e82..71396ecfc574 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c@@ -3525,13 +3525,21 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff, if (skb_is_gso(skb)) { struct skb_shared_info *shinfo = skb_shinfo(skb); - /* Due to header grow, 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 |= gso_type; shinfo->gso_segs = 0; + + /* Due to header grow, MSS needs to be downgraded. + * There is BUG_ON when segment the frag_list with + * head_frag true so linearize skb after downgrade + * the MSS. + */ + if (!(flags & BPF_F_ADJ_ROOM_FIXED_GSO)) { + skb_decrease_gso_size(shinfo, len_diff); + if (shinfo->frag_list) + return skb_linearize(skb); + } + } return 0;
--
2.33.0