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From: ebiederm@xmission.com (Eric W. Biederman)
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	linux-kernel@vger.kernel.org, David Miller <davem@davemloft.net>,
	Greg Kroah-Hartman <greg@kroah.com>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	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>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH v3 10/16] exec: Remove do_execve_file
Date: Wed, 08 Jul 2020 08:08:09 -0500
Message-ID: <87y2nugnnq.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <20200708124148.GP13911@42.do-not-panic.com> (Luis Chamberlain's message of "Wed, 8 Jul 2020 12:41:48 +0000")

Luis Chamberlain <mcgrof@kernel.org> writes:

> On Wed, Jul 08, 2020 at 06:35:25AM +0000, Luis Chamberlain wrote:
>> On Thu, Jul 02, 2020 at 11:41:34AM -0500, Eric W. Biederman wrote:
>> > Now that the last callser has been removed remove this code from exec.
>> > 
>> > For anyone thinking of resurrecing do_execve_file please note that
>> > the code was buggy in several fundamental ways.
>> > 
>> > - It did not ensure the file it was passed was read-only and that
>> >   deny_write_access had been called on it.  Which subtlely breaks
>> >   invaniants in exec.
>> > 
>> > - The caller of do_execve_file was expected to hold and put a
>> >   reference to the file, but an extra reference for use by exec was
>> >   not taken so that when exec put it's reference to the file an
>> >   underflow occured on the file reference count.
>> 
>> Maybe its my growing love with testing, but I'm going to have to partly
>> blame here that we added a new API without any respective testing.
>> Granted, I recall this this patch set could have used more wider review
>> and a bit more patience... but just mentioning this so we try to avoid
>> new api-without-testing with more reason in the future.
>> 
>> But more importantly, *how* could we have caught this? Or how can we
>> catch this sort of stuff better in the future?
>
> Of all the issues you pointed out with do_execve_file(), since upon
> review the assumption *by design* was that LSMs/etc would pick up issues
> with the file *prior* to processing, I think that this file reference
> count issue comes to my attention as the more serious issue which I
> wish we could address *first* before this crusade.
>
> So I have to ask, has anyone *really tried* to give a crack at fixing
> this refcount issue in a smaller way first? Alexei?
>
> I'm not opposed to the removal of do_execve_file(), however if there
> is a reproducible crash / issue with the existing user, this sledge
> hammer seems a bit overkill for older kernels.

It does not matter for older kernels because there is exactly one user.
That one user is just a place holder keeping the code alive until a real
user comes along.

For older kernels the solution is to just mark the bpfilter code broken
in Kconfig and refuse to compile it.  That is the trivial backportable
fix if anyone wants one.

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 [this message]
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
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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