From: Andy Lutomirski <luto@amacapital.net>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>,
Alexei Starovoitov <ast@kernel.org>,
Djalal Harouni <tixxdz@gmail.com>,
Al Viro <viro@zeniv.linux.org.uk>,
"David S. Miller" <davem@davemloft.net>,
Daniel Borkmann <daniel@iogearbox.net>,
Greg KH <gregkh@linuxfoundation.org>,
"Luis R. Rodriguez" <mcgrof@kernel.org>,
Network Development <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel-team <kernel-team@fb.com>,
Linux API <linux-api@vger.kernel.org>
Subject: Re: [PATCH net-next] modules: allow modprobe load regular elf binaries
Date: Thu, 8 Mar 2018 19:54:20 -0800 [thread overview]
Message-ID: <C94A45E9-54A0-446D-86D6-82D06E2A35CD@amacapital.net> (raw)
In-Reply-To: <CA+55aFwRGDPvaCUgMtqnQHb2PZ77JSMQMQVf1znSN+PiV7NR-Q@mail.gmail.com>
> On Mar 8, 2018, at 7:06 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
>
> Honestly, that "read twice" thing may be what scuttles this.
> Initially, I thought it was a non-issue, because anybody who controls
> the module subdirectory enough to rewrite files would be in a position
> to just execute the file itself directly instead.
>
On further consideration, I think there’s another showstopper. This patch is a potentially severe ABI break. Right now, loading a module *copies* it into memory and does not hold a reference to the underlying fs. With the patch applied, all kinds of use cases can break in gnarly ways. Initramfs is maybe okay, but initrd may be screwed. If you load an ET_EXEC module from initrd, then umount it, then clear the ramdisk, something will go horribly wrong. Exactly what goes wrong depends on whether userspace notices that umount() failed. Similarly, if you load one of these modules over a network and then lose your connection, you have a problem.
The “read twice” thing is also bad for another reason: containers. Suppose I have a setup where a container can load a signed module blob. With the read twice code, the container can race and run an entirely different blob outside the container.
next prev parent reply other threads:[~2018-03-09 3:54 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-06 1:34 [PATCH net-next] modules: allow modprobe load regular elf binaries Alexei Starovoitov
2018-03-06 2:13 ` Randy Dunlap
2018-03-06 3:02 ` Alexei Starovoitov
2018-03-06 11:05 ` Greg KH
2018-03-07 1:07 ` Alexei Starovoitov
2018-03-07 3:24 ` Greg KH
2018-03-06 19:12 ` Linus Torvalds
2018-03-06 23:42 ` Chris Mason
2018-05-02 9:12 ` Jesper Dangaard Brouer
2018-03-06 20:01 ` Andy Lutomirski
2018-03-06 20:26 ` Linus Torvalds
2018-03-07 17:22 ` David Miller
2018-03-08 1:23 ` Luis R. Rodriguez
2018-03-08 23:07 ` Alexei Starovoitov
2018-03-09 1:58 ` Luis R. Rodriguez
2018-03-09 0:24 ` Kees Cook
2018-03-09 0:57 ` Alexei Starovoitov
2018-03-09 1:04 ` Andy Lutomirski
2018-03-09 1:25 ` Alexei Starovoitov
2018-03-09 1:24 ` Kees Cook
2018-03-09 0:59 ` Andy Lutomirski
2018-03-09 1:20 ` Alexei Starovoitov
2018-03-09 2:12 ` Andy Lutomirski
2018-03-09 2:31 ` David Miller
2018-03-09 3:10 ` Andy Lutomirski
2018-03-09 3:27 ` Alexei Starovoitov
2018-03-09 1:38 ` Linus Torvalds
2018-03-09 1:44 ` Kees Cook
2018-03-09 3:06 ` Linus Torvalds
2018-03-09 3:17 ` Linus Torvalds
2018-03-09 3:54 ` Andy Lutomirski [this message]
2018-03-09 5:08 ` Alexei Starovoitov
2018-03-09 15:16 ` Andy Lutomirski
2018-03-09 15:39 ` Alexei Starovoitov
2018-03-09 16:24 ` Andy Lutomirski
2018-03-09 17:32 ` Alexei Starovoitov
2018-03-09 18:15 ` Greg KH
2018-03-09 18:23 ` Andy Lutomirski
2018-03-09 18:29 ` Greg KH
2018-03-09 18:50 ` Alexei Starovoitov
2018-03-09 18:55 ` David Miller
2018-03-09 19:37 ` Andy Lutomirski
2018-03-10 1:43 ` Alexei Starovoitov
2018-03-11 2:17 ` Andy Lutomirski
2018-03-09 18:17 ` Linus Torvalds
2018-03-09 18:35 ` David Miller
2018-03-09 18:43 ` Kees Cook
2018-03-09 18:50 ` Linus Torvalds
2018-03-09 18:54 ` Kees Cook
2018-03-09 18:58 ` Alexei Starovoitov
2018-03-12 12:02 ` Edward Cree
2018-03-12 17:49 ` Alexei Starovoitov
2018-03-09 18:48 ` Andy Lutomirski
2018-03-09 18:53 ` Linus Torvalds
2018-03-09 18:57 ` David Miller
2018-03-09 19:12 ` Linus Torvalds
2018-03-09 19:38 ` Linus Torvalds
2018-03-09 19:45 ` Andy Lutomirski
2018-03-10 2:34 ` Alexei Starovoitov
2018-03-10 14:08 ` Luis R. Rodriguez
2018-03-10 15:16 ` Luis R. Rodriguez
2018-03-10 15:34 ` Luis R. Rodriguez
2018-03-12 17:22 ` Alexei Starovoitov
2018-03-13 8:48 ` Greg Kroah-Hartman
2018-03-22 20:54 ` Luis R. Rodriguez
2018-03-22 22:15 ` Andy Lutomirski
2018-03-22 22:21 ` Alexei Starovoitov
2018-03-23 2:47 ` Luis R. Rodriguez
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