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From: "Mickaël Salaün" <mic@digikod.net>
To: Paul Moore <paul@paul-moore.com>
Cc: linux-security-module@vger.kernel.org, selinux@vger.kernel.org,
	linux-audit@redhat.com, io-uring@vger.kernel.org,
	linux-fsdevel@vger.kernel.org,
	Kumar Kartikeya Dwivedi <memxor@gmail.com>,
	Jens Axboe <axboe@kernel.dk>,
	Pavel Begunkov <asml.silence@gmail.com>
Subject: Re: [RFC PATCH v2 5/9] fs: add anon_inode_getfile_secure() similar to anon_inode_getfd_secure()
Date: Thu, 12 Aug 2021 17:35:27 +0200	[thread overview]
Message-ID: <5daa09d2-c4f8-3c57-5643-93d2df00d503@digikod.net> (raw)
In-Reply-To: <CAHC9VhRe3cgYuaV7w-BUwj_i=8_uuy3+5-8oA6QVsdXp3JgVtw@mail.gmail.com>


On 12/08/2021 16:32, Paul Moore wrote:
> On Thu, Aug 12, 2021 at 5:32 AM Mickaël Salaün <mic@digikod.net> wrote:
>> On 11/08/2021 22:48, Paul Moore wrote:
>>> Extending the secure anonymous inode support to other subsystems
>>> requires that we have a secure anon_inode_getfile() variant in
>>> addition to the existing secure anon_inode_getfd() variant.
>>>
>>> Thankfully we can reuse the existing __anon_inode_getfile() function
>>> and just wrap it with the proper arguments.
>>>
>>> Signed-off-by: Paul Moore <paul@paul-moore.com>
>>>
>>> ---
>>> v2:
>>> - no change
>>> v1:
>>> - initial draft
>>> ---
>>>  fs/anon_inodes.c            |   29 +++++++++++++++++++++++++++++
>>>  include/linux/anon_inodes.h |    4 ++++
>>>  2 files changed, 33 insertions(+)
>>>
>>> diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
>>> index a280156138ed..e0c3e33c4177 100644
>>> --- a/fs/anon_inodes.c
>>> +++ b/fs/anon_inodes.c
>>> @@ -148,6 +148,35 @@ struct file *anon_inode_getfile(const char *name,
>>>  }
>>>  EXPORT_SYMBOL_GPL(anon_inode_getfile);
>>>
>>> +/**
>>> + * anon_inode_getfile_secure - Like anon_inode_getfile(), but creates a new
>>> + *                             !S_PRIVATE anon inode rather than reuse the
>>> + *                             singleton anon inode and calls the
>>> + *                             inode_init_security_anon() LSM hook.  This
>>> + *                             allows for both the inode to have its own
>>> + *                             security context and for the LSM to enforce
>>> + *                             policy on the inode's creation.
>>> + *
>>> + * @name:    [in]    name of the "class" of the new file
>>> + * @fops:    [in]    file operations for the new file
>>> + * @priv:    [in]    private data for the new file (will be file's private_data)
>>> + * @flags:   [in]    flags
>>> + * @context_inode:
>>> + *           [in]    the logical relationship with the new inode (optional)
>>> + *
>>> + * The LSM may use @context_inode in inode_init_security_anon(), but a
>>> + * reference to it is not held.  Returns the newly created file* or an error
>>> + * pointer.  See the anon_inode_getfile() documentation for more information.
>>> + */
>>> +struct file *anon_inode_getfile_secure(const char *name,
>>> +                                    const struct file_operations *fops,
>>> +                                    void *priv, int flags,
>>> +                                    const struct inode *context_inode)
>>> +{
>>> +     return __anon_inode_getfile(name, fops, priv, flags,
>>> +                                 context_inode, true);
>>
>> This is not directly related to this patch but why using the "secure"
>> boolean in __anon_inode_getfile() and __anon_inode_getfd() instead of
>> checking that context_inode is not NULL? This would simplify the code,
>> remove this anon_inode_getfile_secure() wrapper and avoid potential
>> inconsistencies.
> 
> The issue is that it is acceptable for the context_inode to be either
> valid or NULL for callers who request the "secure" code path.
> 
> Look at the SELinux implementation of the anonymous inode hook in
> selinux_inode_init_security_anon() and you will see that in cases
> where the context_inode is valid we simply inherit the label from the
> given inode, whereas if context_inode is NULL we do a type transition
> using the requesting task and the anonymous inode's "name".
> 

Indeed.

Acked-by: Mickaël Salaün <mic@linux.microsoft.com>

  reply	other threads:[~2021-08-12 15:35 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-11 20:48 [RFC PATCH v2 0/9] Add LSM access controls and auditing to io_uring Paul Moore
2021-08-11 20:48 ` [RFC PATCH v2 1/9] audit: prepare audit_context for use in calling contexts beyond syscalls Paul Moore
2021-08-11 20:48 ` [RFC PATCH v2 2/9] audit,io_uring,io-wq: add some basic audit support to io_uring Paul Moore
2021-08-11 20:48 ` [RFC PATCH v2 3/9] audit: dev/test patch to force io_uring auditing Paul Moore
2021-08-11 20:48 ` [RFC PATCH v2 4/9] audit: add filtering for io_uring records Paul Moore
2021-08-11 20:48 ` [RFC PATCH v2 5/9] fs: add anon_inode_getfile_secure() similar to anon_inode_getfd_secure() Paul Moore
2021-08-12  9:32   ` Mickaël Salaün
2021-08-12 14:32     ` Paul Moore
2021-08-12 15:35       ` Mickaël Salaün [this message]
2021-08-11 20:48 ` [RFC PATCH v2 6/9] io_uring: convert io_uring to the secure anon inode interface Paul Moore
2021-08-11 20:48 ` [RFC PATCH v2 7/9] lsm,io_uring: add LSM hooks to io_uring Paul Moore
2021-08-11 20:49 ` [RFC PATCH v2 8/9] selinux: add support for the io_uring access controls Paul Moore
2021-08-11 20:49 ` [RFC PATCH v2 9/9] Smack: Brutalist io_uring support with debug Paul Moore
2021-08-31 14:44   ` Paul Moore
2021-08-31 15:03     ` Casey Schaufler
2021-08-31 16:43       ` Paul Moore
2021-08-24 20:57 ` [RFC PATCH v2 0/9] Add LSM access controls and auditing to io_uring Richard Guy Briggs
2021-08-24 22:27   ` Paul Moore
2021-08-25  1:36     ` Richard Guy Briggs
2021-08-26  1:16   ` Richard Guy Briggs
2021-08-26  1:34     ` Paul Moore
2021-08-26 16:32       ` Richard Guy Briggs
2021-08-26 19:14         ` Paul Moore
2021-08-27 13:35           ` Richard Guy Briggs
2021-08-27 19:49             ` Paul Moore
2021-08-28 15:03               ` Richard Guy Briggs
2021-08-29 15:18                 ` Paul Moore
2021-09-01 19:21                   ` Paul Moore
2021-09-10  0:58                     ` Richard Guy Briggs
2021-09-13 19:23                       ` Paul Moore
2021-09-14  1:50                         ` Paul Moore
2021-09-14  2:49                           ` Paul Moore
2021-09-15 12:29                             ` Richard Guy Briggs
2021-09-15 13:02                               ` Steve Grubb
2021-09-15 14:12                               ` Paul Moore

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