Hi Arjun, url: https://github.com/0day-ci/linux/commits/Arjun-Roy/tcp-Sanitize-CMSG-flag... base: https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git e4b62cf7559f2ef9a022de235e5a09a8d7ded520 config: x86_64-randconfig-m001-20210209 (attached as .config) compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; Reported-by: Dan Carpenter <dan.carpenter(a)oracle.com&gt; smatch warnings: net/ipv4/tcp.c:4158 do_tcp_getsockopt() warn: check for integer overflow 'len' vim +/len +4158 net/ipv4/tcp.c 3fdadf7d27e3fb Dmitry Mishin 2006-03-20 3896 static int do_tcp_getsockopt(struct sock *sk, int level, 3fdadf7d27e3fb Dmitry Mishin 2006-03-20 3897 int optname, char __user *optval, int __user *optlen) ^1da177e4c3f41 Linus Torvalds 2005-04-16 3898 { 295f7324ff8d9e Arnaldo Carvalho de Melo 2005-08-09 3899 struct inet_connection_sock *icsk = inet_csk(sk); ^1da177e4c3f41 Linus Torvalds 2005-04-16 3900 struct tcp_sock *tp = tcp_sk(sk); 6fa251663069e0 Nikolay Borisov 2016-02-03 3901 struct net *net = sock_net(sk); ^1da177e4c3f41 Linus Torvalds 2005-04-16 3902 int val, len; "len" is int. [ snip ] 05255b823a6173 Eric Dumazet 2018-04-27 4146 #ifdef CONFIG_MMU 05255b823a6173 Eric Dumazet 2018-04-27 4147 case TCP_ZEROCOPY_RECEIVE: { 7eeba1706eba6d Arjun Roy 2021-01-20 4148 struct scm_timestamping_internal tss; e0fecb289ad3fd Arjun Roy 2020-12-10 4149 struct tcp_zerocopy_receive zc = {}; 05255b823a6173 Eric Dumazet 2018-04-27 4150 int err; 05255b823a6173 Eric Dumazet 2018-04-27 4151 05255b823a6173 Eric Dumazet 2018-04-27 4152 if (get_user(len, optlen)) 05255b823a6173 Eric Dumazet 2018-04-27 4153 return -EFAULT; c8856c05145490 Arjun Roy 2020-02-14 4154 if (len < offsetofend(struct tcp_zerocopy_receive, length)) 05255b823a6173 Eric Dumazet 2018-04-27 4155 return -EINVAL; The problem is that negative values of "len" are type promoted to high positive values. So the fix is to write this as: if (len < 0 || len < offsetofend(struct tcp_zerocopy_receive, length)) return -EINVAL; 110912bdf28392 Arjun Roy 2021-02-11 4156 if (unlikely(len > sizeof(zc))) { 110912bdf28392 Arjun Roy 2021-02-11 4157 err = check_zeroed_user(optval + sizeof(zc), 110912bdf28392 Arjun Roy 2021-02-11 @4158 len - sizeof(zc)); ^^^^^^^^^^^^^^^^ Potentially "len - a negative value". 110912bdf28392 Arjun Roy 2021-02-11 4159 if (err < 1) 110912bdf28392 Arjun Roy 2021-02-11 4160 return err == 0 ? -EINVAL : err; c8856c05145490 Arjun Roy 2020-02-14 4161 len = sizeof(zc); 0b7f41f68710cc Arjun Roy 2020-02-25 4162 if (put_user(len, optlen)) 0b7f41f68710cc Arjun Roy 2020-02-25 4163 return -EFAULT; 0b7f41f68710cc Arjun Roy 2020-02-25 4164 } --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org