From: Greg KH <gregkh@linuxfoundation.org>
To: Alexei Starovoitov <ast@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
davem@davemloft.net, daniel@iogearbox.net,
torvalds@linux-foundation.org, mcgrof@kernel.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com, linux-api@vger.kernel.org
Subject: Re: [PATCH net-next] modules: allow modprobe load regular elf binaries
Date: Tue, 6 Mar 2018 19:24:14 -0800 [thread overview]
Message-ID: <20180307032414.GA24203@kroah.com> (raw)
In-Reply-To: <d4fa4529-8341-8069-b80e-78773b0bb366@fb.com>
On Tue, Mar 06, 2018 at 05:07:45PM -0800, Alexei Starovoitov wrote:
> combining multiple answers...
>
> On 3/6/18 3:05 AM, Greg KH wrote:
> >
> > Any chance you can add a field to your "umh module" type such that a
> > normal 'modinfo' program will be able to notice it is different easily?
>
> ok. handling of modinfo turned out to be straightforward.
> kmod tooling worked fine with simple addition of .modinfo section.
>
> $ modinfo bpfilter
> filename:
> /lib/modules/4.16.0-rc4-00799-g1716f0aa3039-dirty/net/bpfilter/bpfilter.ko
> umh: Y
Nice. But perhaps spell it out, "user_mode_helper"? Anyway,
bikesheding now, sorry, whatever you want to call it is fine with me.
> license: GPL
>
> I will require umh=Y and license to be present.
> umh has to be set to Y for this 'umh modules'
> and taint of kernel will happen if license is not gpl.
Interesting, I like it :)
> Other modinfo like vermagic are not applicable here, since
> umh modules interact with kernel via normal kernel/user abi.
Very true.
> > > Since umh can crash, can be oom-ed by the kernel, killed by admin,
> > > the subsystem that uses them (like bpfilter) need to manage life
> > > time of umh on its own, so module infra doesn't do any accounting
> > > of them. They don't appear in "lsmod" and cannot be "rmmod".
> > > Multiple request_module("umh") will load multiple umh.ko processes.
> > >
> > > Similar to kernel modules the kernel will be tainted if "umh module"
> > > has invalid signature.
> >
> > Shouldn't we fail to load the "module" if the signature is not valid if
> > CONFIG_MODULE_SIG_FORCE=y is enabled, like we do for modules? I run my
> > systems like that, and just "warning" isn't probably a good idea for
> > systems that want to enforce that everything is signed properly?
>
> CONFIG_MODULE_SIG_FORCE=y is already handled by this patch.
> It's checked first for either .ko or umh.ko (before any elf parsing)
> and returns -ENOKEY to user space without any dmesg message.
> I think it's best to keep it as-is.
> The taint and warning is for 'undef SIG_FORCE' and when module
> is signed, but incorrectly.
Ah, sorry, I missed that, thanks for clearing it up.
> > Other than that, one minor question:
> >
> > > @@ -1745,7 +1745,9 @@ static int do_execveat_common(int fd, struct filename *filename,
> > > sched_exec();
> > >
> > > bprm->file = file;
> > > - if (fd == AT_FDCWD || filename->name[0] == '/') {
> > > + if (!filename) {
> > > + bprm->filename = "/dev/null";
> >
> > Why the use of "/dev/null" for the filename here, and elsewhere in the
> > code? While I'm "sure" that everyone really does have /dev/null/
> > mounted in the root namespace, what is the use of it here?
>
> filename is assumed to be non-null in several places further
> down and instead of hacking it everywhere it's cleaner to assign
> some string to it.
> I'll change it to filename = "none"
> Same in umh part.
Thanks, that makes sense.
greg k-h
next prev parent reply other threads:[~2018-03-07 3:24 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 [this message]
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
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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