This is a note to let you know that I've just added the patch titled net: udp: fix UDP header access on Fast/frag0 UDP GRO to the 5.9-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: net-udp-fix-udp-header-access-on-fast-frag0-udp-gro.patch and it can be found in the queue-5.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Mon Nov 16 07:48:29 PM CET 2020 From: Alexander Lobakin <alobakin@xxxxx> Date: Wed, 11 Nov 2020 20:45:25 +0000 Subject: net: udp: fix UDP header access on Fast/frag0 UDP GRO From: Alexander Lobakin <alobakin@xxxxx> [ Upstream commit 4b1a86281cc1d0de46df3ad2cb8c1f86ac07681c ] UDP GRO uses udp_hdr(skb) in its .gro_receive() callback. While it's probably OK for non-frag0 paths (when all headers or even the entire frame are already in skb head), this inline points to junk when using Fast GRO (napi_gro_frags() or napi_gro_receive() with only Ethernet header in skb head and all the rest in the frags) and breaks GRO packet compilation and the packet flow itself. To support both modes, skb_gro_header_fast() + skb_gro_header_slow() are typically used. UDP even has an inline helper that makes use of them, udp_gro_udphdr(). Use that instead of troublemaking udp_hdr() to get rid of the out-of-order delivers. Present since the introduction of plain UDP GRO in 5.0-rc1. Fixes: e20cf8d3f1f7 ("udp: implement GRO for plain UDP sockets.") Cc: Eric Dumazet <edumazet@xxxxxxxxxx> Signed-off-by: Alexander Lobakin <alobakin@xxxxx> Acked-by: Willem de Bruijn <willemb@xxxxxxxxxx> Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/ipv4/udp_offload.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/ipv4/udp_offload.c +++ b/net/ipv4/udp_offload.c @@ -366,7 +366,7 @@ out: static struct sk_buff *udp_gro_receive_segment(struct list_head *head, struct sk_buff *skb) { - struct udphdr *uh = udp_hdr(skb); + struct udphdr *uh = udp_gro_udphdr(skb); struct sk_buff *pp = NULL; struct udphdr *uh2; struct sk_buff *p; Patches currently in stable-queue which might be from alobakin@xxxxx are queue-5.9/net-udp-fix-udp-header-access-on-fast-frag0-udp-gro.patch queue-5.9/virtio-virtio_console-fix-dma-memory-allocation-for-rproc-serial.patch queue-5.9/ethtool-netlink-add-missing-netdev_features_change-call.patch queue-5.9/net-udp-fix-ip-header-access-and-skb-lookup-on-fast-frag0-udp-gro.patch