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From: Luis Chamberlain <mcgrof@kernel.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
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, 8 Jul 2020 13:32:50 +0000
Message-ID: <20200708133250.GH4332@42.do-not-panic.com> (raw)
In-Reply-To: <87y2nugnnq.fsf@x220.int.ebiederm.org>

On Wed, Jul 08, 2020 at 08:08:09AM -0500, Eric W. Biederman wrote:
> 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.

This seals the deal for me, thanks! Carry on, but hey, please add
yourself to MAINTAINERS too :)
 
  Luis

  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 [this message]
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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