Re:Re: [PATCH] mm/vma: Return the exact errno for __split_vma() and mas_store_gfp()

From: 杨晓
Date: Tue Sep 10 2024 - 09:56:20 EST

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In reply to: Liam R. Howlett: "Re: [PATCH] mm/vma: Return the exact errno for __split_vma() and mas_store_gfp()"
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At 2024-09-10 21:37:44, "Dan Carpenter" <dan.carpenter@xxxxxxxxxx> wrote:
>Hi Xiao,
>
>kernel test robot noticed the following build warnings:
>
>url: https://github.com/intel-lab-lkp/linux/commits/Xiao-Yang/mm-vma-Return-the-exact-errno-for-__split_vma-and-mas_store_gfp/20240909-130325
>base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
>patch link: https://lore.kernel.org/r/20240909050226.2053-1-ice_yangxiao%40163.com
>patch subject: [PATCH] mm/vma: Return the exact errno for __split_vma() and mas_store_gfp()
>config: x86_64-randconfig-161-20240910 (https://download.01.org/0day-ci/archive/20240910/202409102026.LOh8J1Lh-lkp@xxxxxxxxx/config)
>compiler: clang version 18.1.5 (https://github.com/llvm/llvm-project 617a15a9eac96088ae5e9134248d8236e34b91b1)
>
>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>
>| Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
>| Closes: https://lore.kernel.org/r/202409102026.LOh8J1Lh-lkp@xxxxxxxxx/
>
>smatch warnings:
>mm/vma.c:1263 vms_gather_munmap_vmas() warn: missing error code 'error'
>
>vim +/error +1263 mm/vma.c
>
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1166 /*
>dba14840905f9e Liam R. Howlett 2024-08-30 1167 * vms_gather_munmap_vmas() - Put all VMAs within a range into a maple tree
>6898c9039bc8e3 Liam R. Howlett 2024-08-30 1168 * for removal at a later date. Handles splitting first and last if necessary
>6898c9039bc8e3 Liam R. Howlett 2024-08-30 1169 * and marking the vmas as isolated.
>6898c9039bc8e3 Liam R. Howlett 2024-08-30 1170 *
>dba14840905f9e Liam R. Howlett 2024-08-30 1171 * @vms: The vma munmap struct
>6898c9039bc8e3 Liam R. Howlett 2024-08-30 1172 * @mas_detach: The maple state tracking the detached tree
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1173 *
>6898c9039bc8e3 Liam R. Howlett 2024-08-30 1174 * Return: 0 on success, -EPERM on mseal vmas, -ENOMEM otherwise
>

>This comment needs to be updated.

Hi Dan,

Thanks for your reply.
It has been updated on my v2 patch[1].

[1]: https://lore.kernel.org/all/tixinevflrciek4bnjwzxv6dwqyokfhrhtmu6qndc7hs2qoizd@iqg2tpjjtwyt/T/

>
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1175 */
>9014b230d88d7f Liam R. Howlett 2024-08-30 1176 int vms_gather_munmap_vmas(struct vma_munmap_struct *vms,
>dba14840905f9e Liam R. Howlett 2024-08-30 1177 struct ma_state *mas_detach)
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1178 {
>01cf21e9e11957 Liam R. Howlett 2024-08-30 1179 struct vm_area_struct *next = NULL;
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1180 int error = -ENOMEM;
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1181
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1182 /*
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1183 * If we need to split any vma, do it now to save pain later.
>20831cd6f814ea Liam R. Howlett 2024-08-30 1184 * Does it split the first one?
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1185 */
>dba14840905f9e Liam R. Howlett 2024-08-30 1186 if (vms->start > vms->vma->vm_start) {
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1187
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1188 /*
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1189 * Make sure that map_count on return from munmap() will
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1190 * not exceed its limit; but let map_count go just above
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1191 * its limit temporarily, to help free resources as expected.
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1192 */
>dba14840905f9e Liam R. Howlett 2024-08-30 1193 if (vms->end < vms->vma->vm_end &&
>63fc66f5b6b18f Liam R. Howlett 2024-08-30 1194 vms->vma->vm_mm->map_count >= sysctl_max_map_count)
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1195 goto map_count_exceeded;
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1196
>df2a7df9a9aa32 Pedro Falcato 2024-08-17 1197 /* Don't bother splitting the VMA if we can't unmap it anyway */
>dba14840905f9e Liam R. Howlett 2024-08-30 1198 if (!can_modify_vma(vms->vma)) {
>df2a7df9a9aa32 Pedro Falcato 2024-08-17 1199 error = -EPERM;
>df2a7df9a9aa32 Pedro Falcato 2024-08-17 1200 goto start_split_failed;
>df2a7df9a9aa32 Pedro Falcato 2024-08-17 1201 }
>df2a7df9a9aa32 Pedro Falcato 2024-08-17 1202
>013545e1b9bca0 Xiao Yang 2024-09-09 1203 error = __split_vma(vms->vmi, vms->vma, vms->start, 1);
>013545e1b9bca0 Xiao Yang 2024-09-09 1204 if (error)
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1205 goto start_split_failed;
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1206 }
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1207 vms->prev = vma_prev(vms->vmi);
>9c3ebeda8fb5a8 Liam R. Howlett 2024-08-30 1208 if (vms->prev)
>9c3ebeda8fb5a8 Liam R. Howlett 2024-08-30 1209 vms->unmap_start = vms->prev->vm_end;
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1210
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1211 /*
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1212 * Detach a range of VMAs from the mm. Using next as a temp variable as
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1213 * it is always overwritten.
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1214 */
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1215 for_each_vma_range(*(vms->vmi), next, vms->end) {
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1216 long nrpages;
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1217
>df2a7df9a9aa32 Pedro Falcato 2024-08-17 1218 if (!can_modify_vma(next)) {
>df2a7df9a9aa32 Pedro Falcato 2024-08-17 1219 error = -EPERM;
>df2a7df9a9aa32 Pedro Falcato 2024-08-17 1220 goto modify_vma_failed;
>df2a7df9a9aa32 Pedro Falcato 2024-08-17 1221 }
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1222 /* Does it split the end? */
>dba14840905f9e Liam R. Howlett 2024-08-30 1223 if (next->vm_end > vms->end) {
>013545e1b9bca0 Xiao Yang 2024-09-09 1224 error = __split_vma(vms->vmi, next, vms->end, 0);
>013545e1b9bca0 Xiao Yang 2024-09-09 1225 if (error)
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1226 goto end_split_failed;
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1227 }
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1228 vma_start_write(next);
>dba14840905f9e Liam R. Howlett 2024-08-30 1229 mas_set(mas_detach, vms->vma_count++);
>013545e1b9bca0 Xiao Yang 2024-09-09 1230 error = mas_store_gfp(mas_detach, next, GFP_KERNEL);
>013545e1b9bca0 Xiao Yang 2024-09-09 1231 if (error)
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1232 goto munmap_gather_failed;
>6898c9039bc8e3 Liam R. Howlett 2024-08-30 1233
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1234 vma_mark_detached(next, true);
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1235 nrpages = vma_pages(next);
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1236
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1237 vms->nr_pages += nrpages;
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1238 if (next->vm_flags & VM_LOCKED)
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1239 vms->locked_vm += nrpages;
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1240
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1241 if (next->vm_flags & VM_ACCOUNT)
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1242 vms->nr_accounted += nrpages;
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1243
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1244 if (is_exec_mapping(next->vm_flags))
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1245 vms->exec_vm += nrpages;
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1246 else if (is_stack_mapping(next->vm_flags))
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1247 vms->stack_vm += nrpages;
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1248 else if (is_data_mapping(next->vm_flags))
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1249 vms->data_vm += nrpages;
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1250
>dba14840905f9e Liam R. Howlett 2024-08-30 1251 if (unlikely(vms->uf)) {
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1252 /*
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1253 * If userfaultfd_unmap_prep returns an error the vmas
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1254 * will remain split, but userland will get a
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1255 * highly unexpected error anyway. This is no
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1256 * different than the case where the first of the two
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1257 * __split_vma fails, but we don't undo the first
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1258 * split, despite we could. This is unlikely enough
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1259 * failure that it's not worth optimizing it for.
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1260 */
>dba14840905f9e Liam R. Howlett 2024-08-30 1261 if (userfaultfd_unmap_prep(next, vms->start, vms->end,
>dba14840905f9e Liam R. Howlett 2024-08-30 1262 vms->uf))
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 @1263 goto userfaultfd_error;
>
>Needs an "error = -ENOMEM;" here. I haven't reviewed this function outside of

>what the zero day bot puts into this email.

Assigning error here also has been done on my v2 patch. Could you try the v2 patch?

Best Regards,
Xiao Yang

>
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1264 }
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1265 #ifdef CONFIG_DEBUG_VM_MAPLE_TREE
>dba14840905f9e Liam R. Howlett 2024-08-30 1266 BUG_ON(next->vm_start < vms->start);
>dba14840905f9e Liam R. Howlett 2024-08-30 1267 BUG_ON(next->vm_start > vms->end);
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1268 #endif
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1269 }
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1270
>17f1ae9b40c6b0 Liam R. Howlett 2024-08-30 1271 vms->next = vma_next(vms->vmi);
>9c3ebeda8fb5a8 Liam R. Howlett 2024-08-30 1272 if (vms->next)
>9c3ebeda8fb5a8 Liam R. Howlett 2024-08-30 1273 vms->unmap_end = vms->next->vm_start;
>49b1b8d6f68310 Lorenzo Stoakes 2024-07-29 1274
>
>--
>0-DAY CI Kernel Test Service
>https://github.com/intel/lkp-tests/wiki

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