This is a note to let you know that I've just added the patch titled udp: properly flush normal packet at GRO time to the 5.13-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: udp-properly-flush-normal-packet-at-gro-time.patch and it can be found in the queue-5.13 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From b43c8909be52f2baca8884f967b418a88424494a Mon Sep 17 00:00:00 2001 From: Paolo Abeni <pabeni@xxxxxxxxxx> Date: Sat, 3 Jul 2021 00:38:43 +0200 Subject: udp: properly flush normal packet at GRO time From: Paolo Abeni <pabeni@xxxxxxxxxx> commit b43c8909be52f2baca8884f967b418a88424494a upstream. If an UDP packet enters the GRO engine but is not eligible for aggregation and is not targeting an UDP tunnel, udp_gro_receive() will not set the flush bit, and packet could delayed till the next napi flush. Fix the issue ensuring non GROed packets traverse skb_gro_flush_final(). Reported-and-tested-by: Matthias Treydte <mt@xxxxxxxxxxxx> Fixes: 18f25dc39990 ("udp: skip L4 aggregation for UDP tunnel packets") Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/ipv4/udp_offload.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/net/ipv4/udp_offload.c +++ b/net/ipv4/udp_offload.c @@ -525,8 +525,10 @@ struct sk_buff *udp_gro_receive(struct l if ((!sk && (skb->dev->features & NETIF_F_GRO_UDP_FWD)) || (sk && udp_sk(sk)->gro_enabled) || NAPI_GRO_CB(skb)->is_flist) - pp = call_gro_receive(udp_gro_receive_segment, head, skb); - return pp; + return call_gro_receive(udp_gro_receive_segment, head, skb); + + /* no GRO, be sure flush the current packet */ + goto out; } if (NAPI_GRO_CB(skb)->encap_mark || Patches currently in stable-queue which might be from pabeni@xxxxxxxxxx are queue-5.13/tcp-consistently-disable-header-prediction-for-mptcp.patch queue-5.13/udp-properly-flush-normal-packet-at-gro-time.patch