Re: [PATCH v1 05/11] landlock: Move filesystem helpers and add a new one

From: "Mickaël Salaün" <mic@digikod.net>
To: Paul Moore <paul@paul-moore.com>
Cc: "James Morris" <jmorris@namei.org>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Jann Horn" <jannh@google.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Konstantin Meskhidze" <konstantin.meskhidze@huawei.com>,
	"Shuah Khan" <shuah@kernel.org>,
	linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	"Mickaël Salaün" <mic@linux.microsoft.com>
Subject: Re: [PATCH v1 05/11] landlock: Move filesystem helpers and add a new one
Date: Thu, 17 Mar 2022 11:42:35 +0100	[thread overview]
Message-ID: <33d4a0fc-1b77-39df-31e9-ba974b851a97@digikod.net> (raw)
In-Reply-To: <CAHC9VhQM33jnJYMz+z1YoNt9=nNceW=TutuGO=x+SSpHW7PMyg@mail.gmail.com>

On 17/03/2022 02:26, Paul Moore wrote:
> On Mon, Feb 21, 2022 at 4:15 PM Mickaël Salaün <mic@digikod.net> wrote:
>>
>> From: Mickaël Salaün <mic@linux.microsoft.com>
>>
>> Move the SB_NOUSER and IS_PRIVATE dentry check to a standalone
>> is_nouser_or_private() helper.  This will be useful for a following
>> commit.
>>
>> Move get_mode_access() and maybe_remove() to make them usable by new
>> code provided by a following commit.
>>
>> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
>> Link: https://lore.kernel.org/r/20220221212522.320243-6-mic@digikod.net
>> ---
>>   security/landlock/fs.c | 87 ++++++++++++++++++++++--------------------
>>   1 file changed, 46 insertions(+), 41 deletions(-)
> 
> One nit-picky comment below, otherwise it looks fine to me.
> 
> Reviewed-by: Paul Moore <paul@paul-moore.com>
> 
>> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
>> index 9662f9fb3cd0..3886f9ad1a60 100644
>> --- a/security/landlock/fs.c
>> +++ b/security/landlock/fs.c
>> @@ -257,6 +257,18 @@ static inline bool unmask_layers(const struct landlock_rule *const rule,
>>          return false;
>>   }
>>
>> +static inline bool is_nouser_or_private(const struct dentry *dentry)
>> +{
>> +       /*
>> +        * Allows access to pseudo filesystems that will never be mountable
>> +        * (e.g. sockfs, pipefs), but can still be reachable through
>> +        * /proc/<pid>/fd/<file-descriptor> .
>> +        */
> 
> I might suggest moving this explanation up to a function header comment block.

Sounds good.

> 
> 
>> +       return (dentry->d_sb->s_flags & SB_NOUSER) ||
>> +                       (d_is_positive(dentry) &&
>> +                        unlikely(IS_PRIVATE(d_backing_inode(dentry))));
>> +}
>> +
>>   static int check_access_path(const struct landlock_ruleset *const domain,
>>                  const struct path *const path,
>>                  const access_mask_t access_request)
> 
> --
> paul-moore.com