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Date: Thu, 13 Jun 2024 08:15:53 +0300
From: Dan Carpenter <dan.carpenter@linaro.org>
To: oe-kbuild@lists.linux.dev,
	Martin Oliveira <martin.oliveira@eideticom.com>,
	linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Cc: lkp@intel.com, oe-kbuild-all@lists.linux.dev,
	Jason Gunthorpe <jgg@ziepe.ca>, Leon Romanovsky <leon@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Tejun Heo <tj@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux Memory Management List <linux-mm@kvack.org>,
	Logan Gunthorpe <logang@deltatee.com>,
	Martin Oliveira <martin.oliveira@eideticom.com>,
	Mike Marciniszyn <mike.marciniszyn@intel.com>,
	Shiraz Saleem <shiraz.saleem@intel.com>,
	Michael Guralnik <michaelgur@nvidia.com>,
	Artemy Kovalyov <artemyko@nvidia.com>
Subject: Re: [PATCH v2 1/4] kernfs: remove page_mkwrite() from
 vm_operations_struct
Message-ID: <11acf031-a778-4ed9-8ece-c6d9aa0bce3f@moroto.mountain>
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In-Reply-To: <20240611182732.360317-2-martin.oliveira@eideticom.com>

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@intel.com/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@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202406130357.6NmgCbMP-lkp@intel.com/

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