Linearize skb when downgrad gso_size to prevent triggering the BUG_ON during segment skb as described in [1]. v5 changes: - add bpf subject prefix. - adjust message to imperative mood. 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@xxxxxxxxx/ [2] https://lore.kernel.org/all/668d5cf1ec330_1c18c32947@xxxxxxxxxxxxxxxxxxxxxx.notmuch/ Fixes: 2be7e212d541 ("bpf: add bpf_skb_adjust_room helper") Signed-off-by: Fred Li <dracodingfly@xxxxxxxxx> --- 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
