5.4-stable review patch. If anyone has any objections, please let me know.
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From: Fred Li dracodingfly@gmail.com
[ Upstream commit fa5ef655615a01533035c6139248c5b33aa27028 ]
Linearize the skb when downgrading gso_size because it may trigger a BUG_ON() later when the skb is segmented as described in [1,2].
Fixes: 2be7e212d5419 ("bpf: add bpf_skb_adjust_room helper") Signed-off-by: Fred Li dracodingfly@gmail.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: Willem de Bruijn willemb@google.com Acked-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/all/20240626065555.35460-2-dracodingfly@gmail.com [1] Link: https://lore.kernel.org/all/668d5cf1ec330_1c18c32947@willemb.c.googlers.com.... [2] Link: https://lore.kernel.org/bpf/20240719024653.77006-1-dracodingfly@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/filter.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c index 3c4dcdc7217e0..f82c27668623c 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -3126,13 +3126,20 @@ 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 growth, MSS needs to be downgraded. + * There is a BUG_ON() when segmenting the frag_list with + * head_frag true, so linearize the skb after downgrading + * 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;