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From: Kuniyuki Iwashima To: Willem de Bruijn , David Ahern , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , Florian Westphal , Kuniyuki Iwashima , Kuniyuki Iwashima , netdev@vger.kernel.org Content-Type: text/plain; charset="UTF-8" In 2023, syzbot found a null-ptr-deref bug triggered when UDP-Lite attempted to charge an skb after the total memory usage for UDP-Lite _and_ UDP exceeded a system-wide threshold, net.ipv4.udp_mem[1]. Since this threshold is shared with UDP, the bug would have been easy to trigger if any real-world applications were using UDP-Lite; however, only syzbot ever stumbled upon it. The bug had persisted since 2016, suggesting that UDP-Lite had remained unused for 7 years at that point. The bug was fixed in commit ad42a35bdfc6 ("udplite: Fix NULL pointer dereference in __sk_mem_raise_allocated()."), and we added another commit be28c14ac8bb ("udplite: Print deprecation notice.") to announce the deprecation plan. Since then, no one has complained, so it is time to officially retire UDP-Lite. This series first removes IPv6 and IPv4 UDP-Lite sockets, then gradually cleans up the remaining dead/unnecessary code within the UDP stack. By removing a bunch of conditionals for UDP-Lite from the fast path, udp_rr with 20,000 flows sees a 10% increase in pps (13.3 Mpps -> 14.7 Mpps) on an AMD EPYC 7B12 (Zen 2) 64-Core Processor platform. [ With FDO, the baseline is much higher and the delta was ~3%, 20.1 Mpps -> 20.7 Mpps ] Before: $ nstat > /dev/null; sleep 1; nstat | grep Udp Udp6InDatagrams 14013408 0.0 Udp6OutDatagrams 14013128 0.0 After: $ nstat > /dev/null; sleep 1; nstat | grep Udp Udp6InDatagrams 15491971 0.0 Udp6OutDatagrams 15491671 0.0 $ ./scripts/bloat-o-meter vmlinux.before vmlinux.after add/remove: 13/75 grow/shrink: 11/75 up/down: 13777/-18401 (-4624) Function old new delta udp4_gro_receive 872 866 -6 udp6_gro_receive 910 903 -7 udp_rcv 32 1727 +1695 udpv6_rcv 32 1450 +1418 __udp4_lib_rcv 2045 - -2045 __udp6_lib_rcv 2084 - -2084 udp_unicast_rcv_skb 160 149 -11 udp6_unicast_rcv_skb 196 181 -15 __udp4_lib_mcast_deliver 925 846 -79 __udp6_lib_mcast_deliver 922 810 -112 __udp4_lib_lookup 973 969 -4 __udp6_lib_lookup 940 929 -11 __udp4_lib_lookup_skb 106 100 -6 __udp6_lib_lookup_skb 71 66 -5 udp4_lib_lookup_skb 132 127 -5 udp6_lib_lookup_skb 87 81 -6 udp_queue_rcv_skb 326 356 +30 udpv6_queue_rcv_skb 331 361 +30 udp_queue_rcv_one_skb 1233 914 -319 udpv6_queue_rcv_one_skb 1250 930 -320 __udp_enqueue_schedule_skb 1067 995 -72 udp_rcv_segment 520 480 -40 udp_post_segment_fix_csum 120 - -120 udp_lib_checksum_complete 200 84 -116 udp_err 27 1103 +1076 udpv6_err 36 1417 +1381 __udp4_lib_err 1112 - -1112 __udp6_lib_err 1448 - -1448 udp_recvmsg 1149 994 -155 udpv6_recvmsg 1349 1294 -55 udp_sendmsg 2730 2648 -82 udp_send_skb 909 681 -228 udpv6_sendmsg 3022 2861 -161 udp_v6_send_skb 1214 952 -262 ... Total: Before=18446744073748075501, After=18446744073748070877, chg -0.00% Changes: v3: Patch 7: Correct ulen < skb->len case in __udp4_lib_rcv() v2: https://lore.kernel.org/netdev/20260305215013.2984628-1-kuniyu@google.com/ Patch 4 : Make udp_seq_ops static Patch 9 : Add a detailed reason in include/uapi/linux/udp.h v1: https://lore.kernel.org/netdev/20260304193034.1870586-1-kuniyu@google.com/ Kuniyuki Iwashima (15): udp: Make udp[46]_seq_show() static. ipv6: Retire UDP-Lite. ipv6: Remove UDP-Lite support for IPV6_ADDRFORM. ipv4: Retire UDP-Lite. udp: Remove UDP-Lite SNMP stats. smack: Remove IPPROTO_UDPLITE support in security_sock_rcv_skb(). udp: Remove partial csum code in RX. udp: Remove partial csum code in TX. udp: Remove UDPLITE_SEND_CSCOV and UDPLITE_RECV_CSCOV. udp: Remove struct proto.h.udp_table. udp: Remove udp_table in struct udp_seq_afinfo. udp: Remove dead check in __udp[46]_lib_lookup() for BPF. udp: Don't pass udptable to IPv6 socket lookup functions. udp: Don't pass udptable to IPv4 socket lookup functions. udp: Don't pass proto to __udp4_lib_rcv() and __udp6_lib_rcv(). include/linux/udp.h | 10 +- include/net/ipv6.h | 2 - include/net/ipv6_stubs.h | 7 +- include/net/netns/mib.h | 5 - include/net/sock.h | 5 +- include/net/transp_v6.h | 3 - include/net/udp.h | 86 +++----- include/net/udplite.h | 88 -------- include/uapi/linux/udp.h | 2 + net/core/filter.c | 5 +- net/ipv4/Makefile | 2 +- net/ipv4/af_inet.c | 12 -- net/ipv4/proc.c | 16 -- net/ipv4/udp.c | 430 ++++++++++++------------------------- net/ipv4/udp_bpf.c | 2 - net/ipv4/udp_diag.c | 128 +++-------- net/ipv4/udp_impl.h | 27 --- net/ipv4/udp_offload.c | 3 +- net/ipv4/udplite.c | 135 ------------ net/ipv6/Makefile | 2 +- net/ipv6/af_inet6.c | 32 +-- net/ipv6/ip6_checksum.c | 2 +- net/ipv6/ipv6_sockglue.c | 17 +- net/ipv6/proc.c | 16 -- net/ipv6/udp.c | 304 ++++++++++---------------- net/ipv6/udp_impl.h | 31 --- net/ipv6/udp_offload.c | 3 +- net/ipv6/udplite.c | 139 ------------ net/rxrpc/output.c | 2 - security/smack/smack_lsm.c | 4 +- 30 files changed, 342 insertions(+), 1178 deletions(-) delete mode 100644 include/net/udplite.h delete mode 100644 net/ipv4/udp_impl.h delete mode 100644 net/ipv4/udplite.c delete mode 100644 net/ipv6/udp_impl.h delete mode 100644 net/ipv6/udplite.c -- 2.53.0.473.g4a7958ca14-goog