Fred Li wrote: > Linearizing skb when downgrade gso_size because it may > trigger the BUG_ON when segment skb as described in [1]. > > v3 changes: > linearize skb if having frag_list as Willem de Bruijn suggested[2]. > > [1] https://lore.kernel.org/all/20240626065555.35460-2-dracodingfly@xxxxxxxxx/ > [2] https://lore.kernel.org/all/668d5cf1ec330_1c18c32947@xxxxxxxxxxxxxxxxxxxxxx.notmuch/ > > Signed-off-by: Fred Li <dracodingfly@xxxxxxxxx> A fix needs a Fixed tag. This might be the original commit that introduced gso_size adjustment, commit 6578171a7ff0c ("bpf: add bpf_skb_change_proto helper") Unless support for frag_list came later. > --- > 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..70919b532d68 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. > + */ Super tiny nit: no capitalization of When in the middle of a sentence. > + if (!(flags & BPF_F_ADJ_ROOM_FIXED_GSO)) { > + skb_decrease_gso_size(shinfo, len_diff); > + if (shinfo->frag_list) > + return skb_linearize(skb); I previously asked whether it was safe to call pskb_expand_head from within a BPF external function. There are actually plenty of existing examples of this, so this is fine. > + } > + > } > > return 0; > -- > 2.33.0 >
