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From: ebiederm@xmission.com (Eric W. Biederman)
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	David Miller <davem@davemloft.net>,
	Greg Kroah-Hartman <greg@kroah.com>,
	Kees Cook <keescook@chromium.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Alexei Starovoitov <ast@kernel.org>,
	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>,
	LSM List <linux-security-module@vger.kernel.org>,
	Casey Schaufler <casey@schaufler-ca.com>
Subject: Re: [PATCH 00/14] Make the user mode driver code a better citizen
Date: Mon, 29 Jun 2020 15:19:59 -0500
Message-ID: <874kqt39qo.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <c99d0cfc-8526-0daf-90b5-33e560efdede@i-love.sakura.ne.jp> (Tetsuo Handa's message of "Mon, 29 Jun 2020 11:20:14 +0900")

Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> writes:

> On 2020/06/29 4:44, Alexei Starovoitov wrote:
>> But all the defensive programming kinda goes against general kernel style.
>> I wouldn't do it. Especially pr_info() ?!
>> Though I don't feel strongly about it.
>
> Honestly speaking, caller should check for errors and print appropriate
> messages. info->wd.mnt->mnt_root != info->wd.dentry indicates that something
> went wrong (maybe memory corruption). But other conditions are not fatal.
> That is, I consider even pr_info() here should be unnecessary.

They were all should never happen cases.  Which is why my patches do:
if (WARN_ON_ONCE(...))

That let's the caller know the messed up very clearly while still
providing a change to continue.

If they were clearly corruption no ones kernel should ever continue
BUG_ON would be appropriate.

>> I would like to generalize elf_header_check() a bit and call it
>> before doing blob_to_mnt() to make sure that all blobs are elf files only.
>> Supporting '#!/bin/bash' or other things as blobs seems wrong to me.

I vote for not worry about things that have never happened, and are
obviously incorrect.

The only points of checks like that is to catch cases where other
developers misunderstand the interface.  When you get to something like
sysfs with lots and lots of users where it is hard to audit there
is real value in sanity checks.  In something like this with very few
users. Just making the code clear should be enough for people not to do
ridiculous things.


In any case Tetsuo I will leave futher sanity checks for you and Alexei
to work out.  It is beyond the scope of my patchset, and they are easy
enough to add as follow on patches.

Eric

  reply index

Thread overview: 136+ 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                             ` [RFC][PATCH] net/bpfilter: Remove this broken and apparently unmantained 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 [this message]
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
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

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