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Subject: Re: BUG: Mount ignores mount options
To:     "Eric W. Biederman" <ebiederm@xmission.com>,
        David Howells <dhowells@redhat.com>
Cc:     viro@zeniv.linux.org.uk,
        John Johansen <john.johansen@canonical.com>,
        Tejun Heo <tj@kernel.org>, selinux@tycho.nsa.gov,
        Paul Moore <paul@paul-moore.com>,
        Li Zefan <lizefan@huawei.com>, linux-api@vger.kernel.org,
        apparmor@lists.ubuntu.com,
        Casey Schaufler <casey@schaufler-ca.com>, fenghua.yu@intel.com,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Eric Biggers <ebiggers@google.com>,
        linux-security-module@vger.kernel.org,
        Johannes Weiner <hannes@cmpxchg.org>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        tomoyo-dev-en@lists.sourceforge.jp, cgroups@vger.kernel.org,
        torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, "Theodore Y. Ts'o" <tytso@mit.edu>,
        Miklos Szeredi <miklos@szeredi.hu>
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 <87d0uqpba5.fsf@xmission.com>
From:   Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Message-ID: <79f05de7-e600-675d-7bbf-c56faafc3134@i-love.sakura.ne.jp>
Date:   Sat, 11 Aug 2018 00:11:47 +0900
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On 2018/08/10 23:05, Eric W. Biederman wrote:
> 
> There is a serious problem with mount options today that fsopen does not
> address.  The problem is that mount options are ignored for block based
> filesystems, and any other type of filesystem that follows the same
> pattern.
> 
> The script below demonstrates this bug.  Showing this bug can cause the
> ext4 "acl" "quota" and "user_xattr" options to be silently ignored.
> 
> fsopen has my nack until it addresses this issue.
> 
> I don't know if we can fix this in the context of sys_mount.  But we if
> we are redoing the option parsing of how we mount filesystems this needs
> to be fixed before we start worrying about bug compatibility.
> 
> Hopefully this report is simple and clear enough that we can at least
> agree on the problem.
> 
> Eric

This might be related to a problem that syzbot is failing to reproduce a problem.

  https://groups.google.com/forum/#!msg/syzkaller-bugs/R03vI7RCVco/0PijCTrcCgAJ

  syzbot found a reproducer, and the reproducer was working until next-20180803.
  But the reproducer is failing to reproduce this problem in next-20180806 despite
  there is no mm related change between next-20180803 and next-20180806.

  Therefore, I suspect that the reproducer is no longer working as intended. And
  there was parser change (David Howells' patch) between next-20180803 and next-20180806.

I'm waiting for response from David Howells...