Hi Jann, kernel test robot noticed the following build errors: [auto build test ERROR on 8cf0b93919e13d1e8d4466eb4080a4c4d9d66d7b] url: https://github.com/intel-lab-lkp/linux/commits/Jann-Horn/mm-Enforce-a-minimal-stack-gap-even-against-inaccessible-VMAs/20241008-065733 base: 8cf0b93919e13d1e8d4466eb4080a4c4d9d66d7b patch link: https://lore.kernel.org/r/20241008-stack-gap-inaccessible-v1-1-848d4d891f21%40google.com patch subject: [PATCH] mm: Enforce a minimal stack gap even against inaccessible VMAs config: parisc-randconfig-r072-20241009 (https://download.01.org/0day-ci/archive/20241009/202410090632.brLG8w0b-lkp@xxxxxxxxx/config) compiler: hppa-linux-gcc (GCC) 14.1.0 reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241009/202410090632.brLG8w0b-lkp@xxxxxxxxx/reproduce) 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 <lkp@xxxxxxxxx> | Closes: https://lore.kernel.org/oe-kbuild-all/202410090632.brLG8w0b-lkp@xxxxxxxxx/ All errors (new ones prefixed by >>): mm/mmap.c: In function 'expand_upwards': >> mm/mmap.c:1069:39: error: 'prev' undeclared (first use in this function) 1069 | if (vma_is_accessible(prev)) | ^~~~ mm/mmap.c:1069:39: note: each undeclared identifier is reported only once for each function it appears in vim +/prev +1069 mm/mmap.c 1036 1037 #if defined(CONFIG_STACK_GROWSUP) 1038 /* 1039 * PA-RISC uses this for its stack. 1040 * vma is the last one with address > vma->vm_end. Have to extend vma. 1041 */ 1042 static int expand_upwards(struct vm_area_struct *vma, unsigned long address) 1043 { 1044 struct mm_struct *mm = vma->vm_mm; 1045 struct vm_area_struct *next; 1046 unsigned long gap_addr; 1047 int error = 0; 1048 VMA_ITERATOR(vmi, mm, vma->vm_start); 1049 1050 if (!(vma->vm_flags & VM_GROWSUP)) 1051 return -EFAULT; 1052 1053 /* Guard against exceeding limits of the address space. */ 1054 address &= PAGE_MASK; 1055 if (address >= (TASK_SIZE & PAGE_MASK)) 1056 return -ENOMEM; 1057 address += PAGE_SIZE; 1058 1059 /* Enforce stack_guard_gap */ 1060 gap_addr = address + stack_guard_gap; 1061 1062 /* Guard against overflow */ 1063 if (gap_addr < address || gap_addr > TASK_SIZE) 1064 gap_addr = TASK_SIZE; 1065 1066 next = find_vma_intersection(mm, vma->vm_end, gap_addr); 1067 if (next && !(next->vm_flags & VM_GROWSUP)) { 1068 /* see comments in expand_downwards() */ > 1069 if (vma_is_accessible(prev)) 1070 return -ENOMEM; 1071 if (address == next->vm_start) 1072 return -ENOMEM; 1073 } 1074 1075 if (next) 1076 vma_iter_prev_range_limit(&vmi, address); 1077 1078 vma_iter_config(&vmi, vma->vm_start, address); 1079 if (vma_iter_prealloc(&vmi, vma)) 1080 return -ENOMEM; 1081 1082 /* We must make sure the anon_vma is allocated. */ 1083 if (unlikely(anon_vma_prepare(vma))) { 1084 vma_iter_free(&vmi); 1085 return -ENOMEM; 1086 } 1087 1088 /* Lock the VMA before expanding to prevent concurrent page faults */ 1089 vma_start_write(vma); 1090 /* 1091 * vma->vm_start/vm_end cannot change under us because the caller 1092 * is required to hold the mmap_lock in read mode. We need the 1093 * anon_vma lock to serialize against concurrent expand_stacks. 1094 */ 1095 anon_vma_lock_write(vma->anon_vma); 1096 1097 /* Somebody else might have raced and expanded it already */ 1098 if (address > vma->vm_end) { 1099 unsigned long size, grow; 1100 1101 size = address - vma->vm_start; 1102 grow = (address - vma->vm_end) >> PAGE_SHIFT; 1103 1104 error = -ENOMEM; 1105 if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) { 1106 error = acct_stack_growth(vma, size, grow); 1107 if (!error) { 1108 /* 1109 * We only hold a shared mmap_lock lock here, so 1110 * we need to protect against concurrent vma 1111 * expansions. anon_vma_lock_write() doesn't 1112 * help here, as we don't guarantee that all 1113 * growable vmas in a mm share the same root 1114 * anon vma. So, we reuse mm->page_table_lock 1115 * to guard against concurrent vma expansions. 1116 */ 1117 spin_lock(&mm->page_table_lock); 1118 if (vma->vm_flags & VM_LOCKED) 1119 mm->locked_vm += grow; 1120 vm_stat_account(mm, vma->vm_flags, grow); 1121 anon_vma_interval_tree_pre_update_vma(vma); 1122 vma->vm_end = address; 1123 /* Overwrite old entry in mtree. */ 1124 vma_iter_store(&vmi, vma); 1125 anon_vma_interval_tree_post_update_vma(vma); 1126 spin_unlock(&mm->page_table_lock); 1127 1128 perf_event_mmap(vma); 1129 } 1130 } 1131 } 1132 anon_vma_unlock_write(vma->anon_vma); 1133 vma_iter_free(&vmi); 1134 validate_mm(mm); 1135 return error; 1136 } 1137 #endif /* CONFIG_STACK_GROWSUP */ 1138 -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki
