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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Stephen Smalley <stephen.smalley.work@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Kees Cook <keescook@chromium.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Alexei Starovoitov <ast@kernel.org>,
	David Miller <davem@davemloft.net>,
	Al Viro <viro@zeniv.linux.org.uk>, bpf <bpf@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Gary Lin <GLin@suse.com>, Bruno Meneguele <bmeneg@redhat.com>,
	linux-security-module <linux-security-module@vger.kernel.org>,
	Casey Schaufler <casey@schaufler-ca.com>
Subject: Re: [RFC][PATCH] net/bpfilter: Remove this broken and apparently unmantained
Date: Thu, 25 Jun 2020 15:25:51 +0200
Message-ID: <20200625132551.GB3526980@kroah.com> (raw)
In-Reply-To: <CAEjxPJ4e9rWWssp0CyM7GM7NP_QKkswHK7URwLZFqo5+wGecQw@mail.gmail.com>

On Thu, Jun 25, 2020 at 08:56:10AM -0400, Stephen Smalley wrote:
> On Wed, Jun 24, 2020 at 7:16 PM Tetsuo Handa
> <penguin-kernel@i-love.sakura.ne.jp> wrote:
> > What is unhappy for pathname based LSMs is that fork_usermode_blob() creates
> > a file with empty filename. I can imagine that somebody would start abusing
> > fork_usermode_blob() as an interface for starting programs like modprobe, hotplug,
> > udevd and sshd. When such situation happened, how fork_usermode_blob() provides
> > information for identifying the intent of such execve() requests?
> >
> > fork_usermode_blob() might also be an unhappy behavior for inode based LSMs (like
> > SELinux and Smack) because it seems that fork_usermode_blob() can't have a chance
> > to associate appropriate security labels based on the content of the byte array
> > because files are created on-demand. Is fork_usermode_blob() friendly to inode
> > based LSMs?
> 
> No, because we cannot label the inode based on the program's purpose
> and therefore cannot configure an automatic transition to a suitable
> security context for the process, unlike call_usermodehelper().

Why, what prevents this?  Can you not just do that based on the "blob
address" or signature of it or something like that?  Right now you all
do this based on inode of a random file on a disk, what's the difference
between a random blob in memory?

> It is
> important to note that the goal of such transitions is not merely to
> restrict the program from doing bad things but also to protect the
> program from untrustworthy inputs, e.g. one can run kmod/modprobe in a
> domain that can only read from authorized kernel modules, prevent
> following untrusted symlinks, etc.  Further, at present, the
> implementation creates the inode via shmem_kernel_file_setup(), which
> is supposed to be for inodes private to the kernel not exposed to
> userspace (hence marked S_PRIVATE), which I believe in this case will
> end up leaving the inode unlabeled but still end up firing checks in
> the bprm hooks on the file inode, thereby potentially yielding denials
> in SELinux on the exec of unlabeled files.  Not exactly what we would
> want.  If users were to switch from using call_usermodehelper() to
> fork_usermode_blob() we would need them to label the inode in some
> manner to reflect the program purpose prior to exec.  I suppose they
> could pass in some string key and SELinux could look it up in policy
> to get a context to use or something.

Sure, that would work.

> On a different note, will the usermode blob be measured by IMA prior
> to execution?  What ensures that the blob was actually embedded in the
> kernel image and wasn't just supplied as data through exploitation of
> a kernel vulnerability or malicious kernel module?

No reason it couldn't be passed to IMA for measuring, if people want to
do that.

thanks,

greg k-h

  reply index

Thread overview: 138+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <87d066vd4y.fsf@x220.int.ebiederm.org>
     [not found] ` <20200611233134.5vofl53dj5wpwp5j@ast-mbp.dhcp.thefacebook.com>
     [not found]   ` <87bllngirv.fsf@x220.int.ebiederm.org>
     [not found]     ` <CAADnVQ+qNxFjTYBpYW9ZhStMh_oJBS5C_FsxSS=0Mzy=u54MSg@mail.gmail.com>
     [not found]       ` <CAADnVQLuGYX=LamARhrZcze1ej4ELj-y99fLzOCgz60XLPw_cQ@mail.gmail.com>
     [not found]         ` <87ftaxd7ky.fsf@x220.int.ebiederm.org>
     [not found]           ` <20200616015552.isi6j5x732okiky4@ast-mbp.dhcp.thefacebook.com>
     [not found]             ` <87h7v1pskt.fsf@x220.int.ebiederm.org>
     [not found]               ` <20200623183520.5e7fmlt3omwa2lof@ast-mbp.dhcp.thefacebook.com>
     [not found]                 ` <87h7v1mx4z.fsf@x220.int.ebiederm.org>
     [not found]                   ` <20200623194023.lzl34qt2wndhcehk@ast-mbp.dhcp.thefacebook.com>
     [not found]                     ` <b4a805e7-e009-dfdf-d011-be636ce5c4f5@i-love.sakura.ne.jp>
     [not found]                       ` <20200624040054.x5xzkuhiw67cywzl@ast-mbp.dhcp.thefacebook.com>
     [not found]                         ` <5254444e-465e-6dee-287b-bef58526b724@i-love.sakura.ne.jp>
     [not found]                           ` <20200624063940.ctzhf4nnh3cjyxqi@ast-mbp.dhcp.thefacebook.com>
2020-06-24  7:05                             ` Tetsuo Handa
2020-06-24 15:41                               ` Casey Schaufler
2020-06-24 17:54                                 ` Alexei Starovoitov
2020-06-24 19:48                                   ` Casey Schaufler
     [not found]                     ` <878sgck6g0.fsf@x220.int.ebiederm.org>
     [not found]                       ` <CAADnVQL8WrfV74v1ChvCKE=pQ_zo+A5EtEBB3CbD=P5ote8_MA@mail.gmail.com>
2020-06-24 23:14                         ` Tetsuo Handa
2020-06-25  1:35                           ` Alexei Starovoitov
2020-06-25  6:38                             ` Tetsuo Handa
2020-06-25  9:57                               ` Greg KH
2020-06-25 11:03                                 ` Tetsuo Handa
2020-06-25 12:07                                   ` Greg KH
2020-06-25 14:21                                     ` Tetsuo Handa
2020-06-25 19:34                                     ` David Miller
2020-06-26  1:36                                       ` Linus Torvalds
2020-06-26  1:51                                         ` Alexei Starovoitov
2020-06-26  4:58                                           ` Tetsuo Handa
2020-06-26  5:41                                             ` Alexei Starovoitov
2020-06-26  6:20                                               ` Tetsuo Handa
2020-06-26  6:39                                                 ` Alexei Starovoitov
2020-06-26 12:51                                         ` [PATCH 00/14] Make the user mode driver code a better citizen Eric W. Biederman
2020-06-26 12:53                                           ` [PATCH 01/14] umh: Capture the pid in umh_pipe_setup Eric W. Biederman
2020-06-26 12:53                                           ` [PATCH 02/14] umh: Move setting PF_UMH into umh_pipe_setup Eric W. Biederman
2020-06-26 12:54                                           ` [PATCH 03/14] umh: Rename the user mode driver helpers for clarity Eric W. Biederman
2020-06-26 12:54                                           ` [PATCH 04/14] umh: Remove call_usermodehelper_setup_file Eric W. Biederman
2020-06-26 12:55                                           ` [PATCH 05/14] umh: Separate the user mode driver and the user mode helper support Eric W. Biederman
2020-06-26 16:22                                             ` Tetsuo Handa
2020-06-26 16:45                                               ` Eric W. Biederman
2020-06-27  1:26                                                 ` Tetsuo Handa
2020-06-27  4:21                                                   ` Eric W. Biederman
2020-06-27  4:36                                                     ` Tetsuo Handa
2020-06-26 12:55                                           ` [PATCH 06/14] umd: For clarity rename umh_info umd_info Eric W. Biederman
2020-06-26 15:37                                             ` Kees Cook
2020-06-26 16:31                                               ` Eric W. Biederman
2020-06-26 12:56                                           ` [PATCH 07/14] umd: Rename umd_info.cmdline umd_info.driver_name Eric W. Biederman
2020-06-26 12:56                                           ` [PATCH 08/14] umd: Transform fork_usermode_blob into fork_usermode_driver Eric W. Biederman
2020-06-26 12:57                                           ` [PATCH 09/14] umh: Stop calling do_execve_file Eric W. Biederman
2020-06-26 12:57                                           ` [PATCH 10/14] exec: Remove do_execve_file Eric W. Biederman
2020-06-26 12:58                                           ` [PATCH 11/14] bpfilter: Move bpfilter_umh back into init data Eric W. Biederman
2020-06-26 12:58                                           ` [PATCH 12/14] umd: Track user space drivers with struct pid Eric W. Biederman
2020-06-26 12:59                                           ` [PATCH 13/14] bpfilter: Take advantage of the facilities of " Eric W. Biederman
2020-06-26 12:59                                           ` [PATCH 14/14] umd: Remove exit_umh Eric W. Biederman
2020-06-26 13:48                                           ` [PATCH 00/14] Make the user mode driver code a better citizen Eric W. Biederman
2020-06-29 19:55                                             ` [PATCH v2 00/15] " Eric W. Biederman
2020-06-29 19:56                                               ` [PATCH v2 01/15] umh: Capture the pid in umh_pipe_setup Eric W. Biederman
2020-06-29 19:57                                               ` [PATCH v2 02/15] umh: Move setting PF_UMH into umh_pipe_setup Eric W. Biederman
2020-06-29 19:57                                               ` [PATCH v2 03/15] umh: Rename the user mode driver helpers for clarity Eric W. Biederman
2020-06-29 19:59                                               ` [PATCH v2 04/15] umh: Remove call_usermodehelper_setup_file Eric W. Biederman
2020-06-29 20:00                                               ` [PATCH v2 05/15] umh: Separate the user mode driver and the user mode helper support Eric W. Biederman
2020-06-30 16:58                                                 ` Linus Torvalds
2020-07-01 17:18                                                   ` Eric W. Biederman
2020-07-01 17:42                                                     ` Alexei Starovoitov
2020-06-29 20:01                                               ` [PATCH v2 06/15] umd: For clarity rename umh_info umd_info Eric W. Biederman
2020-06-29 20:02                                               ` [PATCH v2 07/15] umd: Rename umd_info.cmdline umd_info.driver_name Eric W. Biederman
2020-06-29 20:03                                               ` [PATCH v2 08/15] umd: Transform fork_usermode_blob into fork_usermode_driver Eric W. Biederman
2020-06-29 20:03                                               ` [PATCH v2 09/15] umh: Stop calling do_execve_file Eric W. Biederman
2020-06-29 20:04                                               ` [PATCH v2 10/15] exec: Remove do_execve_file Eric W. Biederman
2020-06-30  5:43                                                 ` Christoph Hellwig
2020-06-30 12:14                                                   ` Eric W. Biederman
2020-06-30 13:38                                                     ` Christoph Hellwig
2020-06-30 14:28                                                       ` Eric W. Biederman
2020-06-30 16:55                                                         ` Alexei Starovoitov
2020-06-29 20:05                                               ` [PATCH v2 11/15] bpfilter: Move bpfilter_umh back into init data Eric W. Biederman
2020-06-29 20:06                                               ` [PATCH v2 12/15] umd: Track user space drivers with struct pid Eric W. Biederman
2020-06-29 20:06                                               ` [PATCH v2 13/15] bpfilter: Take advantage of the facilities of " Eric W. Biederman
2020-06-29 20:07                                               ` [PATCH v2 14/15] umd: Remove exit_umh Eric W. Biederman
2020-06-29 20:08                                               ` [PATCH v2 15/15] umd: Stop using split_argv Eric W. Biederman
2020-06-29 22:12                                               ` [PATCH v2 00/15] Make the user mode driver code a better citizen Alexei Starovoitov
2020-06-30  1:13                                                 ` Eric W. Biederman
2020-06-30  6:16                                                   ` Tetsuo Handa
2020-06-30 12:29                                                 ` Eric W. Biederman
2020-06-30 13:21                                                   ` Tetsuo Handa
2020-07-02 13:08                                                     ` Eric W. Biederman
2020-07-02 13:40                                                       ` Tetsuo Handa
2020-07-02 16:02                                                         ` Eric W. Biederman
2020-07-03 13:19                                                           ` Tetsuo Handa
2020-07-03 22:25                                                             ` Eric W. Biederman
2020-07-04  6:57                                                               ` Tetsuo Handa
2020-07-08  4:46                                                                 ` Eric W. Biederman
2020-06-30 16:52                                                   ` Alexei Starovoitov
2020-07-01 17:12                                                     ` Eric W. Biederman
2020-07-02 16:40                                               ` [PATCH v3 00/16] " Eric W. Biederman
2020-07-02 16:41                                                 ` [PATCH v3 01/16] umh: Capture the pid in umh_pipe_setup Eric W. Biederman
2020-07-02 16:41                                                 ` [PATCH v3 02/16] umh: Move setting PF_UMH into umh_pipe_setup Eric W. Biederman
2020-07-02 16:41                                                 ` [PATCH v3 03/16] umh: Rename the user mode driver helpers for clarity Eric W. Biederman
2020-07-02 16:41                                                 ` [PATCH v3 04/16] umh: Remove call_usermodehelper_setup_file Eric W. Biederman
2020-07-02 16:41                                                 ` [PATCH v3 05/16] umh: Separate the user mode driver and the user mode helper support Eric W. Biederman
2020-07-02 16:41                                                 ` [PATCH v3 06/16] umd: For clarity rename umh_info umd_info Eric W. Biederman
2020-07-02 16:41                                                 ` [PATCH v3 07/16] umd: Rename umd_info.cmdline umd_info.driver_name Eric W. Biederman
2020-07-02 16:41                                                 ` [PATCH v3 08/16] umd: Transform fork_usermode_blob into fork_usermode_driver Eric W. Biederman
2020-07-02 16:41                                                 ` [PATCH v3 09/16] umh: Stop calling do_execve_file Eric W. Biederman
2020-07-02 16:41                                                 ` [PATCH v3 10/16] exec: Remove do_execve_file Eric W. Biederman
2020-07-08  6:35                                                   ` Luis Chamberlain
2020-07-08 12:41                                                     ` Luis Chamberlain
2020-07-08 13:08                                                       ` Eric W. Biederman
2020-07-08 13:32                                                         ` Luis Chamberlain
2020-07-12 21:02                                                   ` Pavel Machek
2020-07-02 16:41                                                 ` [PATCH v3 11/16] bpfilter: Move bpfilter_umh back into init data Eric W. Biederman
2020-07-02 16:41                                                 ` [PATCH v3 12/16] umd: Track user space drivers with struct pid Eric W. Biederman
2020-07-02 16:41                                                 ` [PATCH v3 13/16] exit: Factor thread_group_exited out of pidfd_poll Eric W. Biederman
2020-07-03 20:30                                                   ` Alexei Starovoitov
2020-07-03 21:37                                                     ` Eric W. Biederman
2020-07-04  0:03                                                       ` Alexei Starovoitov
2020-07-04 15:50                                                       ` Christian Brauner
2020-07-07 17:09                                                         ` Eric W. Biederman
2020-07-08  0:05                                                           ` Daniel Borkmann
2020-07-08  3:50                                                             ` Eric W. Biederman
2020-07-04 16:00                                                   ` Christian Brauner
2020-07-02 16:41                                                 ` [PATCH v3 14/16] bpfilter: Take advantage of the facilities of struct pid Eric W. Biederman
2020-07-02 16:41                                                 ` [PATCH v3 15/16] umd: Remove exit_umh Eric W. Biederman
2020-07-02 16:41                                                 ` [PATCH v3 16/16] umd: Stop using split_argv Eric W. Biederman
2020-07-02 23:51                                                 ` [PATCH v3 00/16] Make the user mode driver code a better citizen Tetsuo Handa
2020-07-09 22:05                                                 ` [merged][PATCH " Eric W. Biederman
2020-07-14 19:42                                                   ` Alexei Starovoitov
2020-07-08  5:20                                               ` [PATCH v2 00/15] " Luis Chamberlain
2020-06-26 14:10                                           ` [PATCH 00/14] " Greg Kroah-Hartman
2020-06-26 16:40                                           ` Alexei Starovoitov
2020-06-26 17:17                                             ` Eric W. Biederman
2020-06-26 18:22                                               ` Alexei Starovoitov
2020-06-27 11:38                                           ` Tetsuo Handa
2020-06-27 12:59                                             ` Eric W. Biederman
2020-06-27 13:57                                               ` Tetsuo Handa
2020-06-28 19:44                                                 ` Alexei Starovoitov
2020-06-29  2:20                                                   ` Tetsuo Handa
2020-06-29 20:19                                                     ` Eric W. Biederman
2020-06-30  6:28                                                       ` Tetsuo Handa
2020-06-30 12:32                                                         ` Eric W. Biederman
2020-06-30 16:48                                                         ` Alexei Starovoitov
2020-06-30 21:54                                                           ` Tetsuo Handa
2020-06-30 21:57                                                             ` Alexei Starovoitov
2020-06-30 22:58                                                               ` Tetsuo Handa
2020-06-25 12:56                           ` [RFC][PATCH] net/bpfilter: Remove this broken and apparently unmantained Stephen Smalley
2020-06-25 13:25                             ` Greg Kroah-Hartman [this message]
2020-06-25 14:26                               ` Stephen Smalley
2020-06-25 14:36                                 ` Stephen Smalley
2020-06-25 15:21                                 ` Tetsuo Handa
2020-06-25 16:03                                   ` Stephen Smalley
2020-06-25 16:06                                   ` Casey Schaufler
     [not found] <20200607014935.vhd3scr4qmawq7no@ast-mbp>
     [not found] ` <33cf7a57-0afa-9bb9-f831-61cca6c19eba@i-love.sakura.ne.jp>
     [not found]   ` <20200608162306.iu35p4xoa2kcp3bu@ast-mbp.dhcp.thefacebook.com>
     [not found]     ` <af00d341-6046-e187-f5c8-5f57b40f017c@i-love.sakura.ne.jp>
     [not found]       ` <20200609012826.dssh2lbfr6tlhwwa@ast-mbp.dhcp.thefacebook.com>
     [not found]         ` <ddabab93-4660-3a46-8b05-89385e292b75@i-love.sakura.ne.jp>
     [not found]           ` <20200609223214.43db3orsyjczb2dd@ast-mbp.dhcp.thefacebook.com>
     [not found]             ` <6a8b284f-461e-11b5-9985-6dc70012f774@i-love.sakura.ne.jp>
     [not found]               ` <20200610000546.4hh4n53vaxc4hypi@ast-mbp.dhcp.thefacebook.com>
     [not found]                 ` <1be571d2-c517-d7a7-788e-3bcc07afa858@i-love.sakura.ne.jp>
     [not found]                   ` <20200610033256.xkv5a7l6vtb2jiox@ast-mbp.dhcp.thefacebook.com>
2020-06-10  7:30                     ` Tetsuo Handa
2020-06-10 16:24                       ` Casey Schaufler

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