Re: [PATCH] PCI: optimize proc sequential file read

Dan Carpenter
2024-10-21T07:17:31Z

Hi Guixin,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url: https://github.com/intel-lab-lkp/linux/commits/Guixin-Liu/PCI-optimize-proc-sequential-file-read/20241018-135026
base: https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git next
patch link: https://lore.kernel.org/r/20241018054728.116519-1-kanie%40linux.alibaba.com
patch subject: [PATCH] PCI: optimize proc sequential file read
config: i386-randconfig-141-20241019 (https://download.01.org/0day-ci/archive/20241019/202410190659.9MCI8EyL-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0

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@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202410190659.9MCI8EyL-lkp@intel.com/

smatch warnings:
drivers/pci/proc.c:365 pci_seq_tree_remove_dev() warn: variable dereferenced before check 'dev' (see line 361)

vim +/dev +365 drivers/pci/proc.c

4ca256d9a0e58a Guixin Liu 2024-10-18 359 void pci_seq_tree_remove_dev(struct pci_dev *dev)
4ca256d9a0e58a Guixin Liu 2024-10-18 360 {
4ca256d9a0e58a Guixin Liu 2024-10-18 @361 unsigned long idx = dev->proc_seq_idx;
^^^^^^^^^^^^^^^^^
Dereferenced

4ca256d9a0e58a Guixin Liu 2024-10-18 362 struct pci_dev *latest_dev = NULL;
4ca256d9a0e58a Guixin Liu 2024-10-18 363 struct pci_dev *ret;
4ca256d9a0e58a Guixin Liu 2024-10-18 364
4ca256d9a0e58a Guixin Liu 2024-10-18 @365 if (!dev)
^^^^
Checked too late

4ca256d9a0e58a Guixin Liu 2024-10-18 366 return;
4ca256d9a0e58a Guixin Liu 2024-10-18 367
4ca256d9a0e58a Guixin Liu 2024-10-18 368 xa_lock(&pci_seq_tree);
4ca256d9a0e58a Guixin Liu 2024-10-18 369 __xa_erase(&pci_seq_tree, idx);
4ca256d9a0e58a Guixin Liu 2024-10-18 370 pci_dev_put(dev);
4ca256d9a0e58a Guixin Liu 2024-10-18 371 /*
4ca256d9a0e58a Guixin Liu 2024-10-18 372 * Move the latest pci_dev to this idx to keep the continuity.
4ca256d9a0e58a Guixin Liu 2024-10-18 373 */
4ca256d9a0e58a Guixin Liu 2024-10-18 374 if (idx != pci_max_idx - 1) {
4ca256d9a0e58a Guixin Liu 2024-10-18 375 latest_dev = __xa_erase(&pci_seq_tree, pci_max_idx - 1);
4ca256d9a0e58a Guixin Liu 2024-10-18 376 ret = __xa_cmpxchg(&pci_seq_tree, idx, NULL, latest_dev,
4ca256d9a0e58a Guixin Liu 2024-10-18 377 GFP_KERNEL);
4ca256d9a0e58a Guixin Liu 2024-10-18 378 if (!ret)
4ca256d9a0e58a Guixin Liu 2024-10-18 379 latest_dev->proc_seq_idx = idx;
4ca256d9a0e58a Guixin Liu 2024-10-18 380 WARN_ON(ret);
4ca256d9a0e58a Guixin Liu 2024-10-18 381 }
4ca256d9a0e58a Guixin Liu 2024-10-18 382 pci_max_idx--;
4ca256d9a0e58a Guixin Liu 2024-10-18 383 xa_unlock(&pci_seq_tree);
4ca256d9a0e58a Guixin Liu 2024-10-18 384 }

--
0-DAY CI Kernel Test Service