Hi Kees, [FYI, it's a private test report for your RFC patch.] [auto build test ERROR on tip/sched/core] [also build test ERROR on kees/for-next/pstore linus/master v5.9-rc4] [cannot apply to security/next-testing next-20200911] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch] url: https://github.com/0day-ci/linux/commits/Kees-Cook/Fork-brute-force-attac... base: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git 848785df48835eefebe0c4eb5da7690690b0a8b7 config: microblaze-randconfig-r033-20200911 (attached as .config) compiler: microblaze-linux-gcc (GCC) 9.3.0 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 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=microblaze If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): microblaze-linux-ld: security/fbfam/fbfam.o: in function `fbfam_handle_attack': # https://github.com/0day-ci/linux/commit/2a9c0b8f7327cdab5ef73c9a9a4447d25... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Kees-Cook/Fork-brute-force-attack-mitigation-fbfam/20200911-042512 git checkout 2a9c0b8f7327cdab5ef73c9a9a4447d25c084bca vim +206 security/fbfam/fbfam.c 176 177 /** 178 * fbfam_handle_attack() - Fork brute force attack detection. 179 * @signal: Signal number that causes the core dump. 180 * 181 * The crashing rate of an application is computed in milliseconds per fault in 182 * each crash. So, if this rate goes under a certain threshold there is a clear 183 * signal that the application is crashing quickly. At this moment, a fork brute 184 * force attack is happening. 185 * 186 * Return: -EFAULT if the current task doesn't have statistical data. Zero 187 * otherwise. 188 */ 189 int fbfam_handle_attack(int signal) 190 { 191 struct fbfam_stats *stats = current->fbfam_stats; 192 u64 delta_jiffies, delta_time; 193 u64 crashing_rate; 194 195 if (!stats) 196 return -EFAULT; 197 198 if (!(signal == SIGILL || signal == SIGBUS || signal == SIGKILL || 199 signal == SIGSEGV || signal == SIGSYS)) 200 return 0; 201 202 stats->faults += 1; 203 204 delta_jiffies = get_jiffies_64() - stats->jiffies; 205 delta_time = jiffies64_to_msecs(delta_jiffies); 207 208 if (crashing_rate < (u64)sysctl_crashing_rate_threshold) 209 pr_warn("fbfam: Fork brute force attack detected\n"); 210 211 return 0; 212 } 213 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org