> > > 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") > Yes, this is the original commit, but it's already fixed by commit 364745fbe981a (bpf: Do not change gso_size during bpf_skb_change_proto()) Another commit 2be7e212d5419 (bpf: add bpf_skb_adjust_room helper) introduced gso_size too. > 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. Thanks, i'will fix. > > > + 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 > >
