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From: Amir Goldstein <amir73il@gmail.com>
To: Christian Brauner <brauner@kernel.org>
Cc: Casey Schaufler <casey@schaufler-ca.com>,
	KP Singh <kpsingh@kernel.org>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	bpf <bpf@vger.kernel.org>,
	LSM List <linux-security-module@vger.kernel.org>,
	Linux-Fsdevel <linux-fsdevel@vger.kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Benjamin Tissoires <benjamin.tissoires@redhat.com>,
	Yosry Ahmed <yosryahmed@google.com>,
	Serge Hallyn <serge@hallyn.com>,
	Miklos Szeredi <miklos@szeredi.hu>,
	Tyler Hicks <code@tyhicks.com>
Subject: Re: [PATCH v5 bpf-next 5/5] bpf/selftests: Add a selftest for bpf_getxattr
Date: Fri, 1 Jul 2022 12:24:48 +0300	[thread overview]
Message-ID: <CAOQ4uxgXWa4x9+Ec2PTrztk4ZvPvewLbavg3VpxSFjhJp-v4=A@mail.gmail.com> (raw)
In-Reply-To: <20220701085817.7jzdyqcboj6vkl5m@wittgenstein>

> >
> > Apropos __vfs_getxattr(), looks like ecryptfs_getxattr_lower()
> > is abusing it.
>
> Heh, quoting what I wrote to KP yesterday off-list about
> __vfs_getxattr():
>
> "it's [__vfs_getxattr()] exported but [afaict] it's not used in kernel
> modules. afaict it's only exposed because of ecryptfs"
>
> So right at the beginning I had already pondered whether we should just
> rip out __vfs_getxattr() from ecryptfs and unexport the helper
> completely because there's barely a reason to use it. Module/driver code
> should not use something as low-level as __vfs_getxattr() imho.
>
> Overlayfs does it correctly and uses vfs_getxattr() but maybe ecryptfs
> needs to use it for for some reason?. I haven't looked yet.
>

No reason AFAIK (CC Tyler+Miklos)

Most lower ecryptfs operations use vfs_XXX()
48b512e68571 ("ecryptfs: call vfs_setxattr() in ecryptfs_setxattr()")
fixed vfs_setxattr() which was later changed to __vfs_setxattr_locked(),
but left __vfs_getxattr(), __vfs_removexattr() and i_op->listxattr().

> > Christian, not sure if you intend to spend time of idmapped
> > mount support of ecryptfs lower layer, but anyway that's that.
>
> Not really. Remember the conversation we had with Tyler at LSFMM where
> he considered marking it deprecated. I don't think it's worth putting in
> the work.

OK, so just need a volunteer to close the security hole and
possibly unexport __vfs_getxattr().

Does anybody know of any out of tree modules that use it
for a good reason?

Thanks,
Amir.

  reply	other threads:[~2022-07-01  9:25 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-28 16:19 [PATCH v5 bpf-next 0/5] Add bpf_getxattr KP Singh
2022-06-28 16:19 ` [PATCH v5 bpf-next 1/5] btf: Add a new kfunc set which allows to mark a function to be sleepable KP Singh
2022-06-28 16:19 ` [PATCH v5 bpf-next 2/5] bpf: kfunc support for ARG_PTR_TO_CONST_STR KP Singh
2022-06-28 16:19 ` [PATCH v5 bpf-next 3/5] bpf: Allow kfuncs to be used in LSM programs KP Singh
2022-06-28 16:19 ` [PATCH v5 bpf-next 4/5] bpf: Add a bpf_getxattr kfunc KP Singh
2022-06-28 17:22   ` Christian Brauner
2022-06-28 17:23   ` Al Viro
2022-06-28 17:29     ` KP Singh
2022-06-28 16:19 ` [PATCH v5 bpf-next 5/5] bpf/selftests: Add a selftest for bpf_getxattr KP Singh
2022-06-28 17:33   ` Christian Brauner
2022-06-28 17:52     ` KP Singh
2022-06-28 22:28       ` Alexei Starovoitov
2022-06-29  8:11         ` Christian Brauner
2022-06-29  9:55           ` Christian Brauner
2022-06-30  3:02             ` Alexei Starovoitov
2022-06-30 11:45               ` Christian Brauner
2022-06-30 12:21                 ` KP Singh
2022-06-30 12:23                   ` KP Singh
2022-06-30 13:26                   ` Christian Brauner
2022-06-30 13:29                     ` KP Singh
2022-06-30 13:47                       ` Christian Brauner
2022-06-30 14:37                         ` Christian Brauner
2022-06-30 16:10                         ` Casey Schaufler
2022-06-30 22:23                           ` KP Singh
2022-06-30 23:23                             ` Casey Schaufler
2022-07-01  8:32                               ` Amir Goldstein
2022-07-01  8:58                                 ` Christian Brauner
2022-07-01  9:24                                   ` Amir Goldstein [this message]
2022-06-30 16:28                   ` Amir Goldstein
2022-06-30 22:25                     ` KP Singh
2022-06-28 17:13 ` [PATCH v5 bpf-next 0/5] Add bpf_getxattr Christian Brauner
2022-06-28 17:20   ` KP Singh
2022-06-28 17:21     ` KP Singh
2022-06-29  1:36       ` Dave Chinner
2022-06-29  2:00         ` KP Singh
2022-06-29  2:05           ` KP Singh

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