From: kernel test robot <lkp@intel.com>
To: oe-kbuild@lists.linux.dev
Cc: lkp@intel.com, Dan Carpenter <error27@gmail.com>
Subject: [ljs:project/cow-context 14/18] mm/vma.c:3281 expand_downwards() warn: variable dereferenced before check 'vma->anon_vma' (see line 3263)
Date: Thu, 07 May 2026 19:39:38 +0800 [thread overview]
Message-ID: <202605071933.lpIPQ3YN-lkp@intel.com> (raw)
BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
TO: Lorenzo Stoakes <ljs@kernel.org>
tree: https://git.kernel.org/pub/scm/linux/kernel/git/ljs/linux.git project/cow-context
head: e02aa02fef8128743869032cb20d26f752cd9154
commit: e6f934583c43ab0189504a82904d071b1a22b1a1 [14/18] HACK: track remap changes on merges, splits
:::::: branch date: 6 days ago
:::::: commit date: 6 days ago
config: arc-randconfig-r072-20260507 (https://download.01.org/0day-ci/archive/20260507/202605071933.lpIPQ3YN-lkp@intel.com/config)
compiler: arc-linux-gcc (GCC) 14.3.0
smatch: v0.5.0-9065-ge9cc34fd
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@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202605071933.lpIPQ3YN-lkp@intel.com/
smatch warnings:
mm/vma.c:3281 expand_downwards() warn: variable dereferenced before check 'vma->anon_vma' (see line 3263)
vim +3281 mm/vma.c
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3216
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3217 /*
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3218 * vma is the first one with address < vma->vm_start. Have to extend vma.
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3219 * mmap_lock held for writing.
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3220 */
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3221 int expand_downwards(struct vm_area_struct *vma, unsigned long address)
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3222 {
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3223 struct mm_struct *mm = vma->vm_mm;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3224 struct vm_area_struct *prev;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3225 int error = 0;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3226 VMA_ITERATOR(vmi, mm, vma->vm_start);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3227
769669bd9ca4cba Lorenzo Stoakes (Oracle 2026-03-20 3228) if (!vma_test(vma, VMA_GROWSDOWN_BIT))
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3229 return -EFAULT;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3230
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3231 mmap_assert_write_locked(mm);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3232
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3233 address &= PAGE_MASK;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3234 if (address < mmap_min_addr || address < FIRST_USER_ADDRESS)
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3235 return -EPERM;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3236
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3237 /* Enforce stack_guard_gap */
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3238 prev = vma_prev(&vmi);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3239 /* Check that both stack segments have the same anon_vma? */
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3240 if (prev) {
769669bd9ca4cba Lorenzo Stoakes (Oracle 2026-03-20 3241) if (!vma_test(prev, VMA_GROWSDOWN_BIT) &&
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3242 vma_is_accessible(prev) &&
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3243 (address - prev->vm_end < stack_guard_gap))
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3244 return -ENOMEM;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3245 }
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3246
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3247 if (prev)
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3248 vma_iter_next_range_limit(&vmi, vma->vm_start);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3249
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3250 vma_iter_config(&vmi, address, vma->vm_end);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3251 if (vma_iter_prealloc(&vmi, vma))
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3252 return -ENOMEM;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3253
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3254 /* We must make sure the anon_vma is allocated. */
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3255 if (unlikely(anon_vma_prepare(vma))) {
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3256 vma_iter_free(&vmi);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3257 return -ENOMEM;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3258 }
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3259
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3260 /* Lock the VMA before expanding to prevent concurrent page faults */
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3261 vma_start_write(vma);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3262 /* We update the anon VMA tree. */
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 @3263 anon_vma_lock_write(vma->anon_vma);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3264
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3265 /* Somebody else might have raced and expanded it already */
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3266 if (address < vma->vm_start) {
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3267 unsigned long size, grow;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3268
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3269 size = vma->vm_end - address;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3270 grow = (vma->vm_start - address) >> PAGE_SHIFT;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3271
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3272 error = -ENOMEM;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3273 if (grow <= vma->vm_pgoff) {
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3274 error = acct_stack_growth(vma, size, grow);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3275 if (!error) {
769669bd9ca4cba Lorenzo Stoakes (Oracle 2026-03-20 3276) if (vma_test(vma, VMA_LOCKED_BIT))
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3277 mm->locked_vm += grow;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3278 vm_stat_account(mm, vma->vm_flags, grow);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3279 anon_vma_interval_tree_pre_update_vma(vma);
e6f934583c43ab0 Lorenzo Stoakes 2026-05-01 3280
e6f934583c43ab0 Lorenzo Stoakes 2026-05-01 @3281 if (vma->anon_vma)
e6f934583c43ab0 Lorenzo Stoakes 2026-05-01 3282 cow_context_vma_adjust(vma, address, vma->vm_end);
e6f934583c43ab0 Lorenzo Stoakes 2026-05-01 3283
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3284 vma->vm_start = address;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3285 vma->vm_pgoff -= grow;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3286 /* Overwrite old entry in mtree. */
55e50223bf3e06a Suren Baghdasaryan 2025-02-13 3287 vma_iter_store_overwrite(&vmi, vma);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3288 anon_vma_interval_tree_post_update_vma(vma);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3289
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3290 perf_event_mmap(vma);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3291 }
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3292 }
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3293 }
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3294 anon_vma_unlock_write(vma->anon_vma);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3295 vma_iter_free(&vmi);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3296 validate_mm(mm);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3297 return error;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3298 }
bef5418d1f3dee4 Lorenzo Stoakes 2024-12-03 3299
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
WARNING: multiple messages have this Message-ID (diff)
From: Dan Carpenter <error27@gmail.com>
To: oe-kbuild@lists.linux.dev, Lorenzo Stoakes <ljs@kernel.org>
Cc: lkp@intel.com, oe-kbuild-all@lists.linux.dev
Subject: [ljs:project/cow-context 14/18] mm/vma.c:3281 expand_downwards() warn: variable dereferenced before check 'vma->anon_vma' (see line 3263)
Date: Thu, 7 May 2026 14:47:10 +0300 [thread overview]
Message-ID: <202605071933.lpIPQ3YN-lkp@intel.com> (raw)
Message-ID: <20260507114710.7i-vhZT7gFKfgys6b8Gg_JZtUCXU0flrtog0fqiY3p0@z> (raw)
tree: https://git.kernel.org/pub/scm/linux/kernel/git/ljs/linux.git project/cow-context
head: e02aa02fef8128743869032cb20d26f752cd9154
commit: e6f934583c43ab0189504a82904d071b1a22b1a1 [14/18] HACK: track remap changes on merges, splits
config: arc-randconfig-r072-20260507 (https://download.01.org/0day-ci/archive/20260507/202605071933.lpIPQ3YN-lkp@intel.com/config)
compiler: arc-linux-gcc (GCC) 14.3.0
smatch: v0.5.0-9065-ge9cc34fd
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@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202605071933.lpIPQ3YN-lkp@intel.com/
smatch warnings:
mm/vma.c:3281 expand_downwards() warn: variable dereferenced before check 'vma->anon_vma' (see line 3263)
vim +3281 mm/vma.c
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3221 int expand_downwards(struct vm_area_struct *vma, unsigned long address)
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3222 {
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3223 struct mm_struct *mm = vma->vm_mm;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3224 struct vm_area_struct *prev;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3225 int error = 0;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3226 VMA_ITERATOR(vmi, mm, vma->vm_start);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3227
769669bd9ca4cba Lorenzo Stoakes (Oracle 2026-03-20 3228) if (!vma_test(vma, VMA_GROWSDOWN_BIT))
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3229 return -EFAULT;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3230
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3231 mmap_assert_write_locked(mm);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3232
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3233 address &= PAGE_MASK;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3234 if (address < mmap_min_addr || address < FIRST_USER_ADDRESS)
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3235 return -EPERM;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3236
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3237 /* Enforce stack_guard_gap */
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3238 prev = vma_prev(&vmi);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3239 /* Check that both stack segments have the same anon_vma? */
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3240 if (prev) {
769669bd9ca4cba Lorenzo Stoakes (Oracle 2026-03-20 3241) if (!vma_test(prev, VMA_GROWSDOWN_BIT) &&
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3242 vma_is_accessible(prev) &&
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3243 (address - prev->vm_end < stack_guard_gap))
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3244 return -ENOMEM;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3245 }
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3246
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3247 if (prev)
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3248 vma_iter_next_range_limit(&vmi, vma->vm_start);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3249
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3250 vma_iter_config(&vmi, address, vma->vm_end);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3251 if (vma_iter_prealloc(&vmi, vma))
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3252 return -ENOMEM;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3253
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3254 /* We must make sure the anon_vma is allocated. */
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3255 if (unlikely(anon_vma_prepare(vma))) {
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3256 vma_iter_free(&vmi);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3257 return -ENOMEM;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3258 }
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3259
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3260 /* Lock the VMA before expanding to prevent concurrent page faults */
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3261 vma_start_write(vma);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3262 /* We update the anon VMA tree. */
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 @3263 anon_vma_lock_write(vma->anon_vma);
^^^^^^^^^^^^^
Dereference
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3264
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3265 /* Somebody else might have raced and expanded it already */
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3266 if (address < vma->vm_start) {
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3267 unsigned long size, grow;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3268
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3269 size = vma->vm_end - address;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3270 grow = (vma->vm_start - address) >> PAGE_SHIFT;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3271
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3272 error = -ENOMEM;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3273 if (grow <= vma->vm_pgoff) {
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3274 error = acct_stack_growth(vma, size, grow);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3275 if (!error) {
769669bd9ca4cba Lorenzo Stoakes (Oracle 2026-03-20 3276) if (vma_test(vma, VMA_LOCKED_BIT))
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3277 mm->locked_vm += grow;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3278 vm_stat_account(mm, vma->vm_flags, grow);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3279 anon_vma_interval_tree_pre_update_vma(vma);
e6f934583c43ab0 Lorenzo Stoakes 2026-05-01 3280
e6f934583c43ab0 Lorenzo Stoakes 2026-05-01 @3281 if (vma->anon_vma)
^^^^^^^^^^^^^
Checked in between too unchecked dereference.
e6f934583c43ab0 Lorenzo Stoakes 2026-05-01 3282 cow_context_vma_adjust(vma, address, vma->vm_end);
e6f934583c43ab0 Lorenzo Stoakes 2026-05-01 3283
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3284 vma->vm_start = address;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3285 vma->vm_pgoff -= grow;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3286 /* Overwrite old entry in mtree. */
55e50223bf3e06a Suren Baghdasaryan 2025-02-13 3287 vma_iter_store_overwrite(&vmi, vma);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3288 anon_vma_interval_tree_post_update_vma(vma);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3289
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3290 perf_event_mmap(vma);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3291 }
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3292 }
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3293 }
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3294 anon_vma_unlock_write(vma->anon_vma);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3295 vma_iter_free(&vmi);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3296 validate_mm(mm);
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3297 return error;
a9d1f3f2d7fecbc Lorenzo Stoakes 2024-12-03 3298 }
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
next reply other threads:[~2026-05-07 11:39 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-07 11:39 kernel test robot [this message]
2026-05-07 11:47 ` [ljs:project/cow-context 14/18] mm/vma.c:3281 expand_downwards() warn: variable dereferenced before check 'vma->anon_vma' (see line 3263) Dan Carpenter
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=202605071933.lpIPQ3YN-lkp@intel.com \
--to=lkp@intel.com \
--cc=error27@gmail.com \
--cc=oe-kbuild@lists.linux.dev \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.