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Message-ID: <202410090632.brLG8w0b-lkp@intel.com>
Date: Wed, 9 Oct 2024 06:45:08 +0800
From: kernel test robot <lkp@...el.com>
To: Jann Horn <jannh@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>
Cc: oe-kbuild-all@...ts.linux.dev,
Linux Memory Management List <linux-mm@...ck.org>,
Hugh Dickins <hughd@...gle.com>, Oleg Nesterov <oleg@...hat.com>,
Michal Hocko <mhocko@...e.com>, Helge Deller <deller@....de>,
Vlastimil Babka <vbabka@...e.cz>, Ben Hutchings <bwh@...nel.org>,
Willy Tarreau <w@....eu>, Rik van Riel <riel@...hat.com>,
linux-kernel@...r.kernel.org, stable@...r.kernel.org,
Jann Horn <jannh@...gle.com>
Subject: Re: [PATCH] mm: Enforce a minimal stack gap even against
inaccessible VMAs
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@intel.com/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@intel.com/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@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202410090632.brLG8w0b-lkp@intel.com/
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
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