Hi Kees, I love your patch! Yet something to improve: [auto build test ERROR on char-misc/char-misc-testing] [also build test ERROR on soc/for-next kees/for-next/pstore v5.17-rc4 next-20220216] [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/lkdtm-usercopy-Expand-... base: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git e6cb9c167eeb8f90ab924666c573e69e85e700a0 config: riscv-allmodconfig (https://download.01.org/0day-ci/archive/20220217/202202170604.hO1q7HZU-lk...) compiler: riscv64-linux-gcc (GCC) 11.2.0 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 # https://github.com/0day-ci/linux/commit/aa676e88f535bd79a3e22a1cc70c9b6cc... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Kees-Cook/lkdtm-usercopy-Expand-size-of-out-of-frame-object/20220217-041936 git checkout aa676e88f535bd79a3e22a1cc70c9b6cc51dbbfe # save the config file to linux build tree mkdir build_dir COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=riscv SHELL=/bin/bash drivers/misc/lkdtm/ 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 >>): In file included from include/linux/kernel.h:29, from drivers/misc/lkdtm/lkdtm.h:7, from drivers/misc/lkdtm/usercopy.c:6: drivers/misc/lkdtm/usercopy.c: In function 'do_usercopy_stack': 74 | pr_info("stack : %px\n", (void *)current_stack_pointer); | ^~~~~~~~~~~~~~~~~~~~~ include/linux/printk.h:418:33: note: in definition of macro 'printk_index_wrap' 418 | _p_func(_fmt, ##__VA_ARGS__); \ | ^~~~~~~~~~~ include/linux/printk.h:519:9: note: in expansion of macro 'printk' 519 | printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__) | ^~~~~~ drivers/misc/lkdtm/usercopy.c:74:9: note: in expansion of macro 'pr_info' 74 | pr_info("stack : %px\n", (void *)current_stack_pointer); | ^~~~~~~ drivers/misc/lkdtm/usercopy.c:74:46: note: each undeclared identifier is reported only once for each function it appears in 74 | pr_info("stack : %px\n", (void *)current_stack_pointer); | ^~~~~~~~~~~~~~~~~~~~~ include/linux/printk.h:418:33: note: in definition of macro 'printk_index_wrap' 418 | _p_func(_fmt, ##__VA_ARGS__); \ | ^~~~~~~~~~~ include/linux/printk.h:519:9: note: in expansion of macro 'printk' 519 | printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__) | ^~~~~~ drivers/misc/lkdtm/usercopy.c:74:9: note: in expansion of macro 'pr_info' 74 | pr_info("stack : %px\n", (void *)current_stack_pointer); | ^~~~~~~ vim +74 drivers/misc/lkdtm/usercopy.c 7 #include <linux/slab.h> 8 #include <linux/vmalloc.h> 9 #include <linux/sched/task_stack.h> 10 #include <linux/mman.h> 11 #include <linux/uaccess.h> 12 #include <asm/cacheflush.h> 13 14 /* 15 * Many of the tests here end up using const sizes, but those would 16 * normally be ignored by hardened usercopy, so force the compiler 17 * into choosing the non-const path to make sure we trigger the 18 * hardened usercopy checks by added "unconst" to all the const copies, 19 * and making sure "cache_size" isn't optimized into a const. 20 */ 21 static volatile size_t unconst; 22 static volatile size_t cache_size = 1024; 23 static struct kmem_cache *whitelist_cache; 24 25 static const unsigned char test_text[] = "This is a test.\n"; 26 27 /* 28 * Instead of adding -Wno-return-local-addr, just pass the stack address 29 * through a function to obfuscate it from the compiler. 30 */ 31 static noinline unsigned char *trick_compiler(unsigned char *stack) 32 { 33 return stack + unconst; 34 } 35 36 static noinline unsigned char *do_usercopy_stack_callee(int value) 37 { 38 unsigned char buf[128]; 39 int i; 40 41 /* Exercise stack to avoid everything living in registers. */ 42 for (i = 0; i < sizeof(buf); i++) { 43 buf[i] = value & 0xff; 44 } 45 46 /* 47 * Put the target buffer in the middle of stack allocation 48 * so that we don't step on future stack users regardless 49 * of stack growth direction. 50 */ 51 return trick_compiler(&buf[(128/2)-32]); 52 } 53 54 static noinline void do_usercopy_stack(bool to_user, bool bad_frame) 55 { 56 unsigned long user_addr; 57 unsigned char good_stack[32]; 58 unsigned char *bad_stack; 59 int i; 60 61 /* Exercise stack to avoid everything living in registers. */ 62 for (i = 0; i < sizeof(good_stack); i++) 63 good_stack[i] = test_text[i % sizeof(test_text)]; 64 65 /* This is a pointer to outside our current stack frame. */ 66 if (bad_frame) { 67 bad_stack = do_usercopy_stack_callee((uintptr_t)&bad_stack); 68 } else { 69 /* Put start address just inside stack. */ 70 bad_stack = task_stack_page(current) + THREAD_SIZE; 71 bad_stack -= sizeof(unsigned long); 72 } 73 75 pr_info("good_stack: %px-%px\n", good_stack, good_stack + sizeof(good_stack)); 76 pr_info("bad_stack : %px-%px\n", bad_stack, bad_stack + sizeof(good_stack)); 77 78 user_addr = vm_mmap(NULL, 0, PAGE_SIZE, 79 PROT_READ | PROT_WRITE | PROT_EXEC, 80 MAP_ANONYMOUS | MAP_PRIVATE, 0); 81 if (user_addr >= TASK_SIZE) { 82 pr_warn("Failed to allocate user memory\n"); 83 return; 84 } 85 86 if (to_user) { 87 pr_info("attempting good copy_to_user of local stack\n"); 88 if (copy_to_user((void __user *)user_addr, good_stack, 89 unconst + sizeof(good_stack))) { 90 pr_warn("copy_to_user failed unexpectedly?!\n"); 91 goto free_user; 92 } 93 94 pr_info("attempting bad copy_to_user of distant stack\n"); 95 if (copy_to_user((void __user *)user_addr, bad_stack, 96 unconst + sizeof(good_stack))) { 97 pr_warn("copy_to_user failed, but lacked Oops\n"); 98 goto free_user; 99 } 100 } else { 101 /* 102 * There isn't a safe way to not be protected by usercopy 103 * if we're going to write to another thread's stack. 104 */ 105 if (!bad_frame) 106 goto free_user; 107 108 pr_info("attempting good copy_from_user of local stack\n"); 109 if (copy_from_user(good_stack, (void __user *)user_addr, 110 unconst + sizeof(good_stack))) { 111 pr_warn("copy_from_user failed unexpectedly?!\n"); 112 goto free_user; 113 } 114 115 pr_info("attempting bad copy_from_user of distant stack\n"); 116 if (copy_from_user(bad_stack, (void __user *)user_addr, 117 unconst + sizeof(good_stack))) { 118 pr_warn("copy_from_user failed, but lacked Oops\n"); 119 goto free_user; 120 } 121 } 122 123 free_user: 124 vm_munmap(user_addr, PAGE_SIZE); 125 } 126 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org