From: Aleksa Sarai <cyphar@cyphar.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>,
Jann Horn <jannh@google.com>, Andy Lutomirski <luto@kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Jeff Layton <jlayton@kernel.org>,
"J. Bruce Fields" <bfields@fieldses.org>,
Arnd Bergmann <arnd@arndb.de>,
David Howells <dhowells@redhat.com>,
Eric Biederman <ebiederm@xmission.com>,
Andrew Morton <akpm@linux-foundation.org>,
Alexei Starovoitov <ast@kernel.org>,
Kees Cook <keescook@chromium.org>,
Christian Brauner <christian@brauner.io>,
Tycho Andersen <tycho@tycho.ws>,
David Drysdale <drysdale@google.com>,
Chanho Min <chanho.min@lge.com>, Oleg Nesterov <oleg@redhat.com>,
Aleksa Sarai <asarai@suse.de>,
Linux Containers <containers@lists.linux-foundation.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
kernel list <linux-kernel@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>
Subject: Re: [PATCH v6 5/6] binfmt_*: scope path resolution of interpreters
Date: Sun, 12 May 2019 03:31:13 +1000 [thread overview]
Message-ID: <20190511173113.qhqmv5q5f74povix@yavin> (raw)
In-Reply-To: <CAHk-=whOL-NBso8X5S8s597yZEOMBoU8chkMFVTi8b-ff2qARg@mail.gmail.com>
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On 2019-05-11, Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Sat, May 11, 2019 at 1:21 PM Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >
> > Notice? None of the real problems are about execve or would be solved
> > by any spawn API. You just think that because you've apparently been
> > talking to too many MS people that think fork (and thus indirectly
> > execve()) is bad process management.
>
> Side note: a good policy has been (and remains) to make suid binaries
> not be dynamically linked. And in the absence of that, the dynamic
> linker at least resets the library path when it notices itself being
> dynamic, and it certainly doesn't inherit any open flags from the
> non-trusted environment.
>
> And by the same logic, a suid interpreter must *definitely* should not
> inherit any execve() flags from the non-trusted environment. So I
> think Aleksa's patch to use the passed-in open flags is *exactly* the
> wrong thing to do for security reasons. It doesn't close holes, it
> opens them.
Yup, I've dropped the patch for the next version. (To be honest, I'm not
sure why I included any of the other flags -- the only one that would've
been necessary to deal with CVE-2019-5736 was AT_NO_MAGICLINKS.)
--
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>
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next prev parent reply other threads:[~2019-05-11 17:31 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-06 16:54 [PATCH v6 0/6] namei: resolveat(2) path resolution restriction API Aleksa Sarai
2019-05-06 16:54 ` [PATCH v6 1/6] namei: split out nd->dfd handling to dirfd_path_init Aleksa Sarai
2019-05-06 16:54 ` [PATCH v6 2/6] namei: O_BENEATH-style path resolution flags Aleksa Sarai
2019-05-06 16:54 ` [PATCH v6 3/6] namei: LOOKUP_IN_ROOT: chroot-like path resolution Aleksa Sarai
2019-05-06 16:54 ` [PATCH v6 4/6] namei: aggressively check for nd->root escape on ".." resolution Aleksa Sarai
2019-05-06 16:54 ` [PATCH v6 5/6] binfmt_*: scope path resolution of interpreters Aleksa Sarai
2019-05-06 18:37 ` Jann Horn
2019-05-06 19:17 ` Aleksa Sarai
2019-05-06 23:41 ` Andy Lutomirski
2019-05-08 0:54 ` Aleksa Sarai
2019-05-10 20:41 ` Jann Horn
2019-05-10 21:20 ` Andy Lutomirski
2019-05-10 22:55 ` Jann Horn
2019-05-10 23:36 ` Christian Brauner
2019-05-11 15:49 ` Aleksa Sarai
2019-05-11 17:00 ` Andy Lutomirski
2019-05-11 17:21 ` Linus Torvalds
2019-05-11 17:26 ` Linus Torvalds
2019-05-11 17:31 ` Aleksa Sarai [this message]
2019-05-11 17:43 ` Linus Torvalds
2019-05-11 17:48 ` Christian Brauner
2019-05-11 18:00 ` Aleksa Sarai
2019-05-11 22:39 ` Andy Lutomirski
[not found] ` <CAHk-=wg3+3GfHsHdB4o78jNiPh_5ShrzxBuTN-Y8EZfiFMhCvw@mail.gmail.com>
2019-05-12 10:19 ` Christian Brauner
[not found] ` <9CD2B97D-A6BD-43BE-9040-B410D996A195@amacapital.net>
2019-05-12 10:44 ` Linus Torvalds
2019-05-12 13:35 ` Aleksa Sarai
2019-05-12 13:38 ` Aleksa Sarai
2019-05-12 14:34 ` Andy Lutomirski
2019-05-11 17:26 ` Aleksa Sarai
2019-05-08 0:38 ` Eric W. Biederman
2019-05-10 20:10 ` Jann Horn
2019-05-06 16:54 ` [PATCH v6 6/6] namei: resolveat(2) syscall Aleksa Sarai
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