LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Stephen Smalley <stephen.smalley.work@gmail.com>
To: Kees Cook <keescook@chromium.org>
Cc: "Mickaël Salaün" <mic@digikod.net>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	"Aleksa Sarai" <cyphar@cyphar.com>,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Christian Heimes" <christian@python.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Deven Bowers" <deven.desai@linux.microsoft.com>,
	"Eric Chiang" <ericchiang@google.com>,
	"Florian Weimer" <fweimer@redhat.com>,
	"James Morris" <jmorris@namei.org>, "Jan Kara" <jack@suse.cz>,
	"Jann Horn" <jannh@google.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Lakshmi Ramasubramanian" <nramas@linux.microsoft.com>,
	"Matthew Garrett" <mjg59@google.com>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Michael Kerrisk" <mtk.manpages@gmail.com>,
	"Mickaël Salaün" <mickael.salaun@ssi.gouv.fr>,
	"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>,
	"Thibaut Sautereau" <thibaut.sautereau@ssi.gouv.fr>,
	"Vincent Strubel" <vincent.strubel@ssi.gouv.fr>,
	kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org,
	linux-integrity@vger.kernel.org,
	"LSM List" <linux-security-module@vger.kernel.org>,
	"Linux FS Devel" <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH v5 3/6] fs: Enable to enforce noexec mounts or file exec through O_MAYEXEC
Date: Thu, 14 May 2020 12:10:31 -0400
Message-ID: <CAEjxPJ4R_juwvRbKiCg5OGuhAi1ZuVytK4fKCDT_kT6VKc8iRg@mail.gmail.com> (raw)
In-Reply-To: <202005140830.2475344F86@keescook>

On Thu, May 14, 2020 at 11:45 AM Kees Cook <keescook@chromium.org> wrote:
>
> On Thu, May 14, 2020 at 08:22:01AM -0400, Stephen Smalley wrote:
> > On Wed, May 13, 2020 at 11:05 PM Kees Cook <keescook@chromium.org> wrote:
> > >
> > > On Wed, May 13, 2020 at 04:27:39PM -0700, Kees Cook wrote:
> > > > Like, couldn't just the entire thing just be:
> > > >
> > > > diff --git a/fs/namei.c b/fs/namei.c
> > > > index a320371899cf..0ab18e19f5da 100644
> > > > --- a/fs/namei.c
> > > > +++ b/fs/namei.c
> > > > @@ -2849,6 +2849,13 @@ static int may_open(const struct path *path, int acc_mode, int flag)
> > > >               break;
> > > >       }
> > > >
> > > > +     if (unlikely(mask & MAY_OPENEXEC)) {
> > > > +             if (sysctl_omayexec_enforce & OMAYEXEC_ENFORCE_MOUNT &&
> > > > +                 path_noexec(path))
> > > > +                     return -EACCES;
> > > > +             if (sysctl_omayexec_enforce & OMAYEXEC_ENFORCE_FILE)
> > > > +                     acc_mode |= MAY_EXEC;
> > > > +     }
> > > >       error = inode_permission(inode, MAY_OPEN | acc_mode);
> > > >       if (error)
> > > >               return error;
> > > >
> > >
> > > FYI, I've confirmed this now. Effectively with patch 2 dropped, patch 3
> > > reduced to this plus the Kconfig and sysctl changes, the self tests
> > > pass.
> > >
> > > I think this makes things much cleaner and correct.
> >
> > I think that covers inode-based security modules but not path-based
> > ones (they don't implement the inode_permission hook).  For those, I
> > would tentatively guess that we need to make sure FMODE_EXEC is set on
> > the open file and then they need to check for that in their file_open
> > hooks.
>
> I kept confusing myself about what order things happened in, so I made
> these handy notes about the call graph:
>
> openat2(dfd, char * filename, open_how)
>     do_filp_open(dfd, filename, open_flags)
>         path_openat(nameidata, open_flags, flags)
>             do_open(nameidata, file, open_flags)
>                 may_open(path, acc_mode, open_flag)
>                     inode_permission(inode, MAY_OPEN | acc_mode)
>                         security_inode_permission(inode, acc_mode)
>                 vfs_open(path, file)
>                     do_dentry_open(file, path->dentry->d_inode, open)
>                         if (unlikely(f->f_flags & FMODE_EXEC && !S_ISREG(inode->i_mode))) ...
>                         security_file_open(f)
>                         open()
>
> So, it looks like adding FMODE_EXEC into f_flags in do_open() is needed in
> addition to injecting MAY_EXEC into acc_mode in do_open()? Hmmm

Just do both in build_open_flags() and be done with it? Looks like he
was already setting FMODE_EXEC in patch 1 so we just need to teach
AppArmor/TOMOYO to check for it and perform file execute checking in
that case if !current->in_execve?

  reply index

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-05 15:31 [PATCH v5 0/6] Add support for O_MAYEXEC Mickaël Salaün
2020-05-05 15:31 ` [PATCH v5 1/6] fs: Add support for an O_MAYEXEC flag on openat2(2) Mickaël Salaün
2020-05-12 21:05   ` Kees Cook
2020-05-12 21:40     ` Christian Heimes
2020-05-12 22:56       ` Kees Cook
2020-05-13 10:13     ` Mickaël Salaün
2020-05-05 15:31 ` [PATCH v5 2/6] fs: Add a MAY_EXECMOUNT flag to infer the noexec mount property Mickaël Salaün
2020-05-12 21:09   ` Kees Cook
2020-05-14  8:14     ` Lev R. Oshvang .
2020-05-14 15:48       ` Kees Cook
2020-05-17 16:57         ` Lev R. Oshvang .
2020-05-05 15:31 ` [PATCH v5 3/6] fs: Enable to enforce noexec mounts or file exec through O_MAYEXEC Mickaël Salaün
2020-05-05 15:44   ` Randy Dunlap
2020-05-05 16:55     ` Mickaël Salaün
2020-05-05 17:40       ` Randy Dunlap
2020-05-12 21:48   ` Kees Cook
2020-05-13 11:09     ` Mickaël Salaün
2020-05-13 15:37   ` Stephen Smalley
2020-05-13 23:27     ` Kees Cook
2020-05-14  3:05       ` Kees Cook
2020-05-14 10:12         ` David Laight
2020-05-14 12:22         ` Stephen Smalley
2020-05-14 14:41           ` Kees Cook
2020-05-14 15:52             ` Stephen Smalley
2020-05-14 15:45           ` Kees Cook
2020-05-14 16:10             ` Stephen Smalley [this message]
2020-05-14 19:16               ` Mickaël Salaün
2020-05-15  0:58                 ` Tetsuo Handa
2020-05-15  8:01                 ` How about just O_EXEC? (was Re: [PATCH v5 3/6] fs: Enable to enforce noexec mounts or file exec through O_MAYEXEC) Kees Cook
2020-05-15  8:43                   ` Florian Weimer
2020-05-15 14:37                     ` Kees Cook
2020-05-15 14:43                       ` Florian Weimer
2020-05-15 15:50                         ` Kees Cook
2020-05-18  7:26                           ` Florian Weimer
2020-05-19  2:23                           ` Aleksa Sarai
2020-05-19 10:13                             ` Mickaël Salaün
2020-05-15 11:04                   ` Mickaël Salaün
2020-05-15 15:46                     ` Kees Cook
2020-05-15 18:24                       ` Mickaël Salaün
2020-05-14 19:21       ` [PATCH v5 3/6] fs: Enable to enforce noexec mounts or file exec through O_MAYEXEC Mickaël Salaün
2020-05-05 15:31 ` [PATCH v5 4/6] selftest/openat2: Add tests for O_MAYEXEC enforcing Mickaël Salaün
2020-05-12 21:57   ` Kees Cook
2020-05-13 11:18     ` Mickaël Salaün
2020-05-05 15:31 ` [PATCH v5 5/6] doc: Add documentation for the fs.open_mayexec_enforce sysctl Mickaël Salaün
2020-05-12 22:00   ` Kees Cook
2020-05-13 11:20     ` Mickaël Salaün
2020-05-05 15:31 ` [PATCH v5 6/6] ima: add policy support for the new file open MAY_OPENEXEC flag Mickaël Salaün
2020-05-05 15:36 ` [PATCH v5 0/6] Add support for O_MAYEXEC Mickaël Salaün
2020-05-06 13:58   ` Lev R. Oshvang .
2020-05-06 15:41     ` Aleksa Sarai
2020-05-07  8:30     ` Mickaël Salaün
2020-05-07  8:05 ` David Laight
2020-05-07  8:36   ` Mickaël Salaün
2020-05-07  9:00     ` David Laight
2020-05-07  9:30       ` Mickaël Salaün
2020-05-07  9:44         ` David Laight
2020-05-07 13:38           ` Mickaël Salaün
2020-05-08  7:15             ` Lev R. Oshvang .
2020-05-08 14:01               ` Mimi Zohar

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAEjxPJ4R_juwvRbKiCg5OGuhAi1ZuVytK4fKCDT_kT6VKc8iRg@mail.gmail.com \
    --to=stephen.smalley.work@gmail.com \
    --cc=ast@kernel.org \
    --cc=christian@python.org \
    --cc=corbet@lwn.net \
    --cc=cyphar@cyphar.com \
    --cc=daniel@iogearbox.net \
    --cc=deven.desai@linux.microsoft.com \
    --cc=ericchiang@google.com \
    --cc=fweimer@redhat.com \
    --cc=jack@suse.cz \
    --cc=jannh@google.com \
    --cc=jmorris@namei.org \
    --cc=keescook@chromium.org \
    --cc=kernel-hardening@lists.openwall.com \
    --cc=linux-api@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-integrity@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-security-module@vger.kernel.org \
    --cc=luto@kernel.org \
    --cc=mic@digikod.net \
    --cc=mickael.salaun@ssi.gouv.fr \
    --cc=mjg59@google.com \
    --cc=mtk.manpages@gmail.com \
    --cc=nramas@linux.microsoft.com \
    --cc=philippe.trebuchet@ssi.gouv.fr \
    --cc=scottsh@microsoft.com \
    --cc=sean.j.christopherson@intel.com \
    --cc=sgrubb@redhat.com \
    --cc=shuah@kernel.org \
    --cc=steve.dower@python.org \
    --cc=thibaut.sautereau@ssi.gouv.fr \
    --cc=vincent.strubel@ssi.gouv.fr \
    --cc=viro@zeniv.linux.org.uk \
    --cc=willy@infradead.org \
    --cc=zohar@linux.ibm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git