Re: [PATCH v2 1/4] kernfs: remove page_mkwrite() from vm_operations_struct
From: Dan Carpenter
Date: Thu Jun 13 2024 - 01:16:16 EST
Hi Martin,
kernel test robot noticed the following build warnings:
url: https://github.com/intel-lab-lkp/linux/commits/Martin-Oliveira/kernfs-remove-page_mkwrite-from-vm_operations_struct/20240612-023130
base: 83a7eefedc9b56fe7bfeff13b6c7356688ffa670
patch link: https://lore.kernel.org/r/20240611182732.360317-2-martin.oliveira%40eideticom.com
patch subject: [PATCH v2 1/4] kernfs: remove page_mkwrite() from vm_operations_struct
config: i386-randconfig-141-20240612 (https://download.01.org/0day-ci/archive/20240613/202406130357.6NmgCbMP-lkp@xxxxxxxxx/config)
compiler: gcc-12 (Ubuntu 12.3.0-9ubuntu2) 12.3.0
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/202406130357.6NmgCbMP-lkp@xxxxxxxxx/
smatch warnings:
fs/kernfs/file.c:462 kernfs_fop_mmap() error: we previously assumed 'vma->vm_ops' could be null (see line 459)
vim +462 fs/kernfs/file.c
c637b8acbe079e Tejun Heo 2013-12-11 416 static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
414985ae23c031 Tejun Heo 2013-11-28 417 {
c525aaddc366df Tejun Heo 2013-12-11 418 struct kernfs_open_file *of = kernfs_of(file);
414985ae23c031 Tejun Heo 2013-11-28 419 const struct kernfs_ops *ops;
414985ae23c031 Tejun Heo 2013-11-28 420 int rc;
414985ae23c031 Tejun Heo 2013-11-28 421
9b2db6e1894577 Tejun Heo 2013-12-10 422 /*
9b2db6e1894577 Tejun Heo 2013-12-10 423 * mmap path and of->mutex are prone to triggering spurious lockdep
9b2db6e1894577 Tejun Heo 2013-12-10 424 * warnings and we don't want to add spurious locking dependency
9b2db6e1894577 Tejun Heo 2013-12-10 425 * between the two. Check whether mmap is actually implemented
9b2db6e1894577 Tejun Heo 2013-12-10 426 * without grabbing @of->mutex by testing HAS_MMAP flag. See the
c810729fe6471a Ahelenia Ziemiańska 2023-12-21 427 * comment in kernfs_fop_open() for more details.
9b2db6e1894577 Tejun Heo 2013-12-10 428 */
df23fc39bce03b Tejun Heo 2013-12-11 429 if (!(of->kn->flags & KERNFS_HAS_MMAP))
9b2db6e1894577 Tejun Heo 2013-12-10 430 return -ENODEV;
9b2db6e1894577 Tejun Heo 2013-12-10 431
414985ae23c031 Tejun Heo 2013-11-28 432 mutex_lock(&of->mutex);
414985ae23c031 Tejun Heo 2013-11-28 433
414985ae23c031 Tejun Heo 2013-11-28 434 rc = -ENODEV;
c637b8acbe079e Tejun Heo 2013-12-11 435 if (!kernfs_get_active(of->kn))
414985ae23c031 Tejun Heo 2013-11-28 436 goto out_unlock;
414985ae23c031 Tejun Heo 2013-11-28 437
324a56e16e44ba Tejun Heo 2013-12-11 438 ops = kernfs_ops(of->kn);
414985ae23c031 Tejun Heo 2013-11-28 439 rc = ops->mmap(of, vma);
b44b2140265ddf Tejun Heo 2014-04-20 440 if (rc)
b44b2140265ddf Tejun Heo 2014-04-20 441 goto out_put;
414985ae23c031 Tejun Heo 2013-11-28 442
414985ae23c031 Tejun Heo 2013-11-28 443 /*
414985ae23c031 Tejun Heo 2013-11-28 444 * PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup()
414985ae23c031 Tejun Heo 2013-11-28 445 * to satisfy versions of X which crash if the mmap fails: that
414985ae23c031 Tejun Heo 2013-11-28 446 * substitutes a new vm_file, and we don't then want bin_vm_ops.
414985ae23c031 Tejun Heo 2013-11-28 447 */
414985ae23c031 Tejun Heo 2013-11-28 448 if (vma->vm_file != file)
414985ae23c031 Tejun Heo 2013-11-28 449 goto out_put;
414985ae23c031 Tejun Heo 2013-11-28 450
414985ae23c031 Tejun Heo 2013-11-28 451 rc = -EINVAL;
414985ae23c031 Tejun Heo 2013-11-28 452 if (of->mmapped && of->vm_ops != vma->vm_ops)
414985ae23c031 Tejun Heo 2013-11-28 453 goto out_put;
414985ae23c031 Tejun Heo 2013-11-28 454
414985ae23c031 Tejun Heo 2013-11-28 455 /*
414985ae23c031 Tejun Heo 2013-11-28 456 * It is not possible to successfully wrap close.
414985ae23c031 Tejun Heo 2013-11-28 457 * So error if someone is trying to use close.
414985ae23c031 Tejun Heo 2013-11-28 458 */
414985ae23c031 Tejun Heo 2013-11-28 @459 if (vma->vm_ops && vma->vm_ops->close)
^^^^^^^^^^^
If ->vm_ops is NULL
414985ae23c031 Tejun Heo 2013-11-28 460 goto out_put;
414985ae23c031 Tejun Heo 2013-11-28 461
927bb8d619fea4 Martin Oliveira 2024-06-11 @462 if (vma->vm_ops->page_mkwrite)
^^^^^^^^^^^^^^^^^^^^^^^^^
then we're in trouble
927bb8d619fea4 Martin Oliveira 2024-06-11 463 goto out_put;
927bb8d619fea4 Martin Oliveira 2024-06-11 464
414985ae23c031 Tejun Heo 2013-11-28 465 rc = 0;
05d8f255867e31 Neel Natu 2024-01-27 466 if (!of->mmapped) {
a1d82aff5df760 Tejun Heo 2016-12-27 467 of->mmapped = true;
bdb2fd7fc56e19 Tejun Heo 2022-08-27 468 of_on(of)->nr_mmapped++;
414985ae23c031 Tejun Heo 2013-11-28 469 of->vm_ops = vma->vm_ops;
05d8f255867e31 Neel Natu 2024-01-27 470 }
414985ae23c031 Tejun Heo 2013-11-28 471 vma->vm_ops = &kernfs_vm_ops;
414985ae23c031 Tejun Heo 2013-11-28 472 out_put:
c637b8acbe079e Tejun Heo 2013-12-11 473 kernfs_put_active(of->kn);
414985ae23c031 Tejun Heo 2013-11-28 474 out_unlock:
414985ae23c031 Tejun Heo 2013-11-28 475 mutex_unlock(&of->mutex);
414985ae23c031 Tejun Heo 2013-11-28 476
414985ae23c031 Tejun Heo 2013-11-28 477 return rc;
414985ae23c031 Tejun Heo 2013-11-28 478 }
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki