Hi Marco, kernel test robot noticed the following build warnings:
https://git-scm.com/docs/git-format-patch#_base_tree_information] url: https://github.com/intel-lab-lkp/linux/commits/Marco-Elver/slab-support-for-compiler-assisted-type-based-slab-cache-partitioning/20260401-035608 base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything patch link: https://lore.kernel.org/r/20260331111240.153913-1-elver%40google.com patch subject: [PATCH v1] slab: support for compiler-assisted type-based slab cache partitioning config: um-randconfig-r072-20260401 compiler: gcc-14 (Debian 14.2.0-19) 14.2.0 smatch: v0.5.0-9004-gb810ac53 If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot <[email protected]> | Reported-by: Dan Carpenter <[email protected]> | Closes: https://lore.kernel.org/r/[email protected]/ New smatch warnings: drivers/misc/lkdtm/heap.c:118 lkdtm_READ_AFTER_FREE() warn: potential pointer math issue ('base' is a 32 bit pointer) drivers/misc/lkdtm/heap.c:169 lkdtm_KFENCE_READ_AFTER_FREE() warn: potential pointer math issue ('base' is a 32 bit pointer) vim +118 drivers/misc/lkdtm/heap.c 73f62e60d80c2d drivers/misc/lkdtm/heap.c Kees Cook 2022-03-03 92 static void lkdtm_READ_AFTER_FREE(void) ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 93 { ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 94 int *base, *val, saw; ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 95 size_t len = 1024; ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 96 /* e12145cf1c3a80 drivers/misc/lkdtm/heap.c Kees Cook 2020-06-25 97 * The slub allocator will use the either the first word or e12145cf1c3a80 drivers/misc/lkdtm/heap.c Kees Cook 2020-06-25 98 * the middle of the allocation to store the free pointer, e12145cf1c3a80 drivers/misc/lkdtm/heap.c Kees Cook 2020-06-25 99 * depending on configurations. Store in the second word to e12145cf1c3a80 drivers/misc/lkdtm/heap.c Kees Cook 2020-06-25 100 * avoid running into the freelist. ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 101 */ e12145cf1c3a80 drivers/misc/lkdtm/heap.c Kees Cook 2020-06-25 102 size_t offset = sizeof(*base); ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 103 ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 104 base = kmalloc(len, GFP_KERNEL); ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 105 if (!base) { ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 106 pr_info("Unable to allocate base memory.\n"); ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 107 return; ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 108 } ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 109 ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 110 val = kmalloc(len, GFP_KERNEL); ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 111 if (!val) { ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 112 pr_info("Unable to allocate val memory.\n"); ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 113 kfree(base); ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 114 return; ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 115 } ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 116 ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 117 *val = 0x12345678; ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 @118 base[offset] = *val; This doesn't really matter, but the comment says we are writing to the second word. The base[] array holds 256 integers, so: base[sizeof(int)] = *val; would be the third word, right? A word is unsigned long, right? All of a sudden I am unsure. :P ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 119 pr_info("Value in memory before free: %x\n", base[offset]); ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 120 ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 121 kfree(base); ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 122 ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 123 pr_info("Attempting bad read from freed memory\n"); ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 124 saw = base[offset]; ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 125 if (saw != *val) { ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 126 /* Good! Poisoning happened, so declare a win. */ ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 127 pr_info("Memory correctly poisoned (%x)\n", saw); 5b777131bd8005 drivers/misc/lkdtm/heap.c Kees Cook 2021-06-23 128 } else { 5b777131bd8005 drivers/misc/lkdtm/heap.c Kees Cook 2021-06-23 129 pr_err("FAIL: Memory was not poisoned!\n"); 5b777131bd8005 drivers/misc/lkdtm/heap.c Kees Cook 2021-06-23 130 pr_expected_config_param(CONFIG_INIT_ON_FREE_DEFAULT_ON, "init_on_free"); ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 131 } ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 132 ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 133 kfree(val); ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 134 } ffc514f3fcac4a drivers/misc/lkdtm_heap.c Kees Cook 2016-06-26 135 aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 136 static void lkdtm_KFENCE_READ_AFTER_FREE(void) aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 137 { aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 138 int *base, val, saw; aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 139 unsigned long timeout, resched_after; aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 140 size_t len = 1024; aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 141 /* aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 142 * The slub allocator will use the either the first word or aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 143 * the middle of the allocation to store the free pointer, aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 144 * depending on configurations. Store in the second word to aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 145 * avoid running into the freelist. aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 146 */ aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 147 size_t offset = sizeof(*base); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 148 aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 149 /* aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 150 * 100x the sample interval should be more than enough to ensure we get aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 151 * a KFENCE allocation eventually. aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 152 */ aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 153 timeout = jiffies + msecs_to_jiffies(100 * kfence_sample_interval); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 154 /* aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 155 * Especially for non-preemption kernels, ensure the allocation-gate aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 156 * timer can catch up: after @resched_after, every failed allocation aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 157 * attempt yields, to ensure the allocation-gate timer is scheduled. aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 158 */ aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 159 resched_after = jiffies + msecs_to_jiffies(kfence_sample_interval); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 160 do { aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 161 base = kmalloc(len, GFP_KERNEL); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 162 if (!base) { aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 163 pr_err("FAIL: Unable to allocate kfence memory!\n"); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 164 return; aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 165 } aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 166 aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 167 if (is_kfence_address(base)) { aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 168 val = 0x12345678; aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 @169 base[offset] = val; ^^^^^^^^^^^^^^^^^^ Same here. aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 170 pr_info("Value in memory before free: %x\n", base[offset]); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 171 aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 172 kfree(base); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 173 aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 174 pr_info("Attempting bad read from freed memory\n"); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 175 saw = base[offset]; aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 176 if (saw != val) { aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 177 /* Good! Poisoning happened, so declare a win. */ aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 178 pr_info("Memory correctly poisoned (%x)\n", saw); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 179 } else { aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 180 pr_err("FAIL: Memory was not poisoned!\n"); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 181 pr_expected_config_param(CONFIG_INIT_ON_FREE_DEFAULT_ON, "init_on_free"); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 182 } aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 183 return; aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 184 } aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 185 aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 186 kfree(base); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 187 if (time_after(jiffies, resched_after)) aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 188 cond_resched(); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 189 } while (time_before(jiffies, timeout)); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 190 aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 191 pr_err("FAIL: kfence memory never allocated!\n"); aabf7c37dfbce3 drivers/misc/lkdtm/heap.c Stephen Boyd 2023-11-29 192 } -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki
