Hi, Thanks Salvatore for the quick follow up on IRC and for pointing me at the following doc in order to quickly rebuild the kernel with the proposed patches.
https://kernel-team.pages.debian.net/kernel-handbook/ch-common-tasks.html#id-1.6.6.4 Le Mon, Aug 26, 2024 at 10:54:41AM +0200, David Prévot a écrit : […] > Forwarded: https://bugzilla.kernel.org/show_bug.cgi?id=219129 […] > It seems real network issues have been noticed in some VMs we rebooted > on friday (they are now running the previous kernel). There are indeed severe consequences in network performances: e.g., it took me two minutes instead of a fraction of second to upload the patched kernel to the server (~500kB/s instead of 62MB/s). > The forwarded upstream issue seems to match. I just rebuilt the kernel with the three following patches and can’t reproduce the issue once booted on the patched version. > 89add40066f9 ("net: drop bad gso csum_start and offset in virtio_net_hdr") > fc8b2a619469 ("net: more strict VIRTIO_NET_HDR_GSO_UDP_L4 validation") > 9840036786d9 ("gso: fix dodgy bit handling for GSO_UDP_L4") The first patch (in reverse order) didn’t apply cleanly, so I only used the first diff (out of three): Index: linux-6.1.106/net/ipv4/udp_offload.c =================================================================== --- linux-6.1.106.orig/net/ipv4/udp_offload.c 2024-08-26 14:01:13.869618434 +0200 +++ linux-6.1.106/net/ipv4/udp_offload.c 2024-08-26 14:01:13.869618434 +0200 @@ -273,13 +273,20 @@ __sum16 check; __be16 newlen; - if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST) - return __udp_gso_segment_list(gso_skb, features, is_ipv6); - mss = skb_shinfo(gso_skb)->gso_size; if (gso_skb->len <= sizeof(*uh) + mss) return ERR_PTR(-EINVAL); + if (skb_gso_ok(gso_skb, features | NETIF_F_GSO_ROBUST)) { + /* Packet is from an untrusted source, reset gso_segs. */ + skb_shinfo(gso_skb)->gso_segs = DIV_ROUND_UP(gso_skb->len - sizeof(*uh), + mss); + return NULL; + } + + if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST) + return __udp_gso_segment_list(gso_skb, features, is_ipv6); + skb_pull(gso_skb, sizeof(*uh)); /* clear destructor to avoid skb_segment assigning it to tail */ Regards taffit
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