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From: Florian Weimer <fweimer@redhat.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Mickaël Salaün" <mic@digikod.net>,
	linux-kernel@vger.kernel.org, "Aleksa Sarai" <cyphar@cyphar.com>,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Christian Brauner" <christian.brauner@ubuntu.com>,
	"Christian Heimes" <christian@python.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Deven Bowers" <deven.desai@linux.microsoft.com>,
	"Dmitry Vyukov" <dvyukov@google.com>,
	"Eric Biggers" <ebiggers@kernel.org>,
	"Eric Chiang" <ericchiang@google.com>,
	"James Morris" <jmorris@namei.org>, "Jan Kara" <jack@suse.cz>,
	"Jann Horn" <jannh@google.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Kees Cook" <keescook@chromium.org>,
	"Lakshmi Ramasubramanian" <nramas@linux.microsoft.com>,
	"Matthew Garrett" <mjg59@google.com>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Michael Kerrisk" <mtk.manpages@gmail.com>,
	"Mimi Zohar" <zohar@linux.ibm.com>,
	"Philippe Trébuchet" <philippe.trebuchet@ssi.gouv.fr>,
	"Scott Shell" <scottsh@microsoft.com>,
	"Sean Christopherson" <sean.j.christopherson@intel.com>,
	"Shuah Khan" <shuah@kernel.org>,
	"Steve Dower" <steve.dower@python.org>,
	"Steve Grubb" <sgrubb@redhat.com>,
	"Tetsuo Handa" <penguin-kernel@i-love.sakura.ne.jp>,
	"Thibaut Sautereau" <thibaut.sautereau@clip-os.org>,
	"Vincent Strubel" <vincent.strubel@ssi.gouv.fr>,
	kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org,
	linux-integrity@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-fsdevel@vger.kernel.org,
	"Thibaut Sautereau" <thibaut.sautereau@ssi.gouv.fr>
Subject: Re: [PATCH v7 4/7] fs: Introduce O_MAYEXEC flag for openat2(2)
Date: Mon, 27 Jul 2020 07:27:00 +0200	[thread overview]
Message-ID: <87y2n55xzv.fsf@oldenburg2.str.redhat.com> (raw)
In-Reply-To: <20200727042106.GB794331@ZenIV.linux.org.uk> (Al Viro's message of "Mon, 27 Jul 2020 05:21:06 +0100")

* Al Viro:

> On Thu, Jul 23, 2020 at 07:12:24PM +0200, Mickaël Salaün wrote:
>> When the O_MAYEXEC flag is passed, openat2(2) may be subject to
>> additional restrictions depending on a security policy managed by the
>> kernel through a sysctl or implemented by an LSM thanks to the
>> inode_permission hook.  This new flag is ignored by open(2) and
>> openat(2) because of their unspecified flags handling.  When used with
>> openat2(2), the default behavior is only to forbid to open a directory.
>
> Correct me if I'm wrong, but it looks like you are introducing a magical
> flag that would mean "let the Linux S&M take an extra special whip
> for this open()".
>
> Why is it done during open?  If the caller is passing it deliberately,
> why not have an explicit request to apply given torture device to an
> already opened file?  Why not sys_masochism(int fd, char *hurt_flavour),
> for that matter?

While I do not think this is appropriate language for a workplace, Al
has a point: If the auditing event can be generated on an already-open
descriptor, it would also cover scenarios like this one:

  perl < /path/to/script

Where the process that opens the file does not (and cannot) know that it
will be used for execution purposes.

Thanks,
Florian


  reply	other threads:[~2020-07-27  5:27 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-23 17:12 [PATCH v7 0/7] Add support for O_MAYEXEC Mickaël Salaün
2020-07-23 17:12 ` [PATCH v7 1/7] exec: Change uselib(2) IS_SREG() failure to EACCES Mickaël Salaün
2020-08-11 18:59   ` Eric W. Biederman
2020-08-11 19:14     ` Eric W. Biederman
2020-07-23 17:12 ` [PATCH v7 2/7] exec: Move S_ISREG() check earlier Mickaël Salaün
2020-08-11 19:27   ` Eric W. Biederman
2020-07-23 17:12 ` [PATCH v7 3/7] exec: Move path_noexec() " Mickaël Salaün
2020-08-11 19:36   ` Eric W. Biederman
2020-08-13 15:31     ` Mickaël Salaün
2020-07-23 17:12 ` [PATCH v7 4/7] fs: Introduce O_MAYEXEC flag for openat2(2) Mickaël Salaün
2020-07-24 19:03   ` Kees Cook
2020-07-27  4:21   ` Al Viro
2020-07-27  5:27     ` Florian Weimer [this message]
2020-07-27 19:46       ` Mickaël Salaün
2020-08-11 19:51   ` Eric W. Biederman
2020-08-13 14:36     ` Mickaël Salaün
2020-07-23 17:12 ` [PATCH v7 5/7] fs,doc: Enable to enforce noexec mounts or file exec through O_MAYEXEC Mickaël Salaün
2020-07-24 19:03   ` Kees Cook
2020-08-11 19:58   ` Eric W. Biederman
2020-08-13 14:49     ` Mickaël Salaün
2020-07-23 17:12 ` [PATCH v7 6/7] selftest/openat2: Add tests for O_MAYEXEC enforcing Mickaël Salaün
2020-07-24 19:03   ` Kees Cook
2020-07-23 17:12 ` [PATCH v7 7/7] ima: add policy support for the new file open MAY_OPENEXEC flag Mickaël Salaün
2020-07-24 19:04   ` Kees Cook
2020-07-24 11:20 ` [PATCH v7 0/7] Add support for O_MAYEXEC Thibaut Sautereau
2020-07-24 19:06 ` Kees Cook
2020-07-25 11:15   ` Christian Brauner
2020-08-10 20:11   ` Mickaël Salaün
2020-08-10 20:21     ` Al Viro
2020-08-10 22:09       ` David Laight
2020-08-10 22:28         ` Al Viro
2020-08-10 22:47           ` Mickaël Salaün
2020-08-11  8:09             ` David Laight
2020-08-11  8:50               ` Mickaël Salaün
2020-08-11 13:07                 ` Steve Grubb
2020-08-10 22:43       ` Mickaël Salaün
2020-08-10 23:03         ` Jann Horn
2020-08-11  8:48           ` Mickaël Salaün
2020-08-11 13:56             ` Mimi Zohar
2020-08-11 14:02               ` Matthew Wilcox
2020-08-11 14:30                 ` Mimi Zohar
2020-08-11 17:18             ` Deven Bowers
2020-08-10 23:05         ` Al Viro
2020-08-11  8:49           ` Mickaël Salaün

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