Hi Hoang, FYI, the error/warning still remains. tree: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-4.9.y head: b76c99cf586bd7e2078de72e6ca5195be58b0dbf commit: 310014f572a59b311c175321265a08c9adfced0c [1640/2200] tipc: fix NULL deref in tipc_link_xmit() config: powerpc64-randconfig-r033-20210412 (attached as .config) compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 9829f5e6b1bca9b61efc629770d28bb9014dec45) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install powerpc64 cross compiling tool for clang build # apt-get install binutils-powerpc64-linux-gnu # https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.gi... git remote add linux-stable-rc https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git git fetch --no-tags linux-stable-rc linux-4.9.y git checkout 310014f572a59b311c175321265a08c9adfced0c # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=powerpc64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): net/tipc/link.c:299:5: warning: no previous prototype for function 'tipc_link_is_active' [-Wmissing-prototypes] int tipc_link_is_active(struct tipc_link *l) ^ net/tipc/link.c:299:1: note: declare 'static' if the function is not intended to be used outside of this translation unit int tipc_link_is_active(struct tipc_link *l) ^ static net/tipc/link.c:375:5: warning: no previous prototype for function 'link_bc_rcv_gap' [-Wmissing-prototypes] u16 link_bc_rcv_gap(struct tipc_link *l) ^ net/tipc/link.c:375:1: note: declare 'static' if the function is not intended to be used outside of this translation unit u16 link_bc_rcv_gap(struct tipc_link *l) ^ static net/tipc/link.c:819:6: warning: no previous prototype for function 'link_prepare_wakeup' [-Wmissing-prototypes] void link_prepare_wakeup(struct tipc_link *l) ^ net/tipc/link.c:819:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void link_prepare_wakeup(struct tipc_link *l) ^ static imp = msg_importance(hdr); ^~~ net/tipc/link.c:890:22: note: initialize the variable 'hdr' to silence this warning struct tipc_msg *hdr; ^ = NULL net/tipc/link.c:959:6: warning: no previous prototype for function 'tipc_link_advance_backlog' [-Wmissing-prototypes] void tipc_link_advance_backlog(struct tipc_link *l, struct sk_buff_head *xmitq) ^ net/tipc/link.c:959:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void tipc_link_advance_backlog(struct tipc_link *l, struct sk_buff_head *xmitq) ^ static net/tipc/link.c:1002:5: warning: no previous prototype for function 'tipc_link_retrans' [-Wmissing-prototypes] int tipc_link_retrans(struct tipc_link *l, u16 from, u16 to, ^ net/tipc/link.c:1002:1: note: declare 'static' if the function is not intended to be used outside of this translation unit int tipc_link_retrans(struct tipc_link *l, u16 from, u16 to, ^ static 6 warnings generated. vim +/hdr +896 net/tipc/link.c 865 866 /** 867 * tipc_link_xmit(): enqueue buffer list according to queue situation 868 * @link: link to use 869 * @list: chain of buffers containing message 870 * @xmitq: returned list of packets to be sent by caller 871 * 872 * Consumes the buffer chain, except when returning -ELINKCONG, 873 * since the caller then may want to make more send attempts. 874 * Returns 0 if success, or errno: -ELINKCONG, -EMSGSIZE or -ENOBUFS 875 * Messages at TIPC_SYSTEM_IMPORTANCE are always accepted 876 */ 877 int tipc_link_xmit(struct tipc_link *l, struct sk_buff_head *list, 878 struct sk_buff_head *xmitq) 879 { 880 unsigned int maxwin = l->window; 881 unsigned int i; 882 unsigned int mtu = l->mtu; 883 u16 ack = l->rcv_nxt - 1; 884 u16 seqno = l->snd_nxt; 885 u16 bc_ack = l->bc_rcvlink->rcv_nxt - 1; 886 struct sk_buff_head *transmq = &l->transmq; 887 struct sk_buff_head *backlogq = &l->backlogq; 888 struct sk_buff *skb, *_skb, *bskb; 889 int pkt_cnt = skb_queue_len(list); 890 struct tipc_msg *hdr; 891 int imp; 892 893 if (pkt_cnt <= 0) 894 return 0; 895 897 /* Match msg importance against this and all higher backlog limits: */ 898 if (!skb_queue_empty(backlogq)) { 899 for (i = imp; i <= TIPC_SYSTEM_IMPORTANCE; i++) { 900 if (unlikely(l->backlog[i].len >= l->backlog[i].limit)) 901 return link_schedule_user(l, list); 902 } 903 } 904 905 hdr = buf_msg(skb_peek(list)); 906 if (unlikely(msg_size(hdr) > mtu)) { 907 skb_queue_purge(list); 908 return -EMSGSIZE; 909 } 910 911 if (pkt_cnt > 1) { 912 l->stats.sent_fragmented++; 913 l->stats.sent_fragments += pkt_cnt; 914 } 915 916 /* Prepare each packet for sending, and add to relevant queue: */ 917 while (skb_queue_len(list)) { 918 skb = skb_peek(list); 919 hdr = buf_msg(skb); 920 msg_set_seqno(hdr, seqno); 921 msg_set_ack(hdr, ack); 922 msg_set_bcast_ack(hdr, bc_ack); 923 924 if (likely(skb_queue_len(transmq) < maxwin)) { 925 _skb = skb_clone(skb, GFP_ATOMIC); 926 if (!_skb) { 927 skb_queue_purge(list); 928 return -ENOBUFS; 929 } 930 __skb_dequeue(list); 931 __skb_queue_tail(transmq, skb); 932 __skb_queue_tail(xmitq, _skb); 933 TIPC_SKB_CB(skb)->ackers = l->ackers; 934 l->rcv_unacked = 0; 935 l->stats.sent_pkts++; 936 seqno++; 937 continue; 938 } 939 if (tipc_msg_bundle(skb_peek_tail(backlogq), hdr, mtu)) { 940 kfree_skb(__skb_dequeue(list)); 941 l->stats.sent_bundled++; 942 continue; 943 } 944 if (tipc_msg_make_bundle(&bskb, hdr, mtu, l->addr)) { 945 kfree_skb(__skb_dequeue(list)); 946 __skb_queue_tail(backlogq, bskb); 947 l->backlog[msg_importance(buf_msg(bskb))].len++; 948 l->stats.sent_bundled++; 949 l->stats.sent_bundles++; 950 continue; 951 } 952 l->backlog[imp].len += skb_queue_len(list); 953 skb_queue_splice_tail_init(list, backlogq); 954 } 955 l->snd_nxt = seqno; 956 return 0; 957 } 958 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org