Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <0c336a41-54fb-2904-42e2-1d9ee3950b21@gmail.com>
Date:   Tue, 13 Jun 2023 12:34:30 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101
 Thunderbird/102.11.0
Content-Language: en-US
From:   Tuo Li <islituo@gmail.com>
Subject: [BUG] ntfs: possible data races in ntfs_clear_extent_inode()
To:     anton@tuxera.com, linkinjeon@kernel.org
Cc:     linux-ntfs-dev@lists.sourceforge.net,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        baijiaju1990@outlook.com
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk

Hello,

Our static analysis tool finds some possible data races in the NTFS file
system in Linux 6.4.0-rc6.

In most calling contexts, the variable ni->ext.base_ntfs_ino is accessed
with holding the lock ni->extent_lock. Here is an example:

   ntfs_extent_mft_record_free() --> Line 2773 in fs/ntfs/mtf.c
     mutex_lock(&ni->extent_lock); --> Line 2786 in fs/ntfs/mtf.c (Lock 
ni->extent_lock)
     base_ni = ni->ext.base_ntfs_ino; --> Line 2787 in fs/ntfs/mft.c 
(Access ni->ext.base_ntfs_ino)

However, in the following calling contexts:

   ntfs_evict_big_inode() --> Line 2247 in fs/ntfs/inode.c
      ntfs_clear_extent_inode() --> Line 2274 in fs/ntfs/inode.c
         if (!is_bad_inode(VFS_I(ni->ext.base_ntfs_ino))) --> Line 2224 
in fs/ntfs/inode.c (Access ni->ext.base_ntfs_ino)

   ntfs_evict_big_inode() --> Line 2247 in fs/ntfs/inode.c
     ni->ext.base_ntfs_ino = NULL; --> Line 2285 in fs/ntfs/inode.c 
(Access ni->ext.base_ntfs_ino)

the variable ni->ext.base_ntfs_ino is accessed without holding the lock
ni->extent_lock, and thus data races can occur.

I am not quite sure whether these possible data races are real and how 
to fix them if they are real.
Any feedback would be appreciated, thanks!

Reported-by: BassCheck <bass@buaa.edu.cn>

Best wishes,
Tuo Li