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Re: [RFC 0/3] extend kexec_file_load system call

From Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Newsgroups linux.kernel
Subject Re: [RFC 0/3] extend kexec_file_load system call
Date 2016-07-20 18:00 +0200
Message-ID <rX24F-3jb-1@gated-at.bofh.it> (permalink)
References <rUkAN-6XH-7@gated-at.bofh.it> <rWVcS-7sY-31@gated-at.bofh.it> <rWXHI-HL-13@gated-at.bofh.it>
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Am Mittwoch, 20 Juli 2016, 13:12:20 schrieb Arnd Bergmann:
> On Wednesday, July 20, 2016 8:47:45 PM CEST Michael Ellerman wrote:
> > At least for stdout-path, I can't really see how that would
> > significantly help an attacker, but I'm all ears if anyone has ideas.
> 
> That's actually an easy one that came up before: If an attacker controls
> a tty device (e.g. network console) that can be used to enter a debugger
> (kdb, kgdb, xmon, ...), enabling that to be the console device
> gives you a direct attack vector. The same thing will happen if you
> have a piece of software that intentially gives extra rights to the
> owner of the console device by treating it as "physical presence".

I think people are talking past each other a bit in these arguments about 
what is relevant to security or not.

For the kexec maintainers, kexec_file_load has one very specific and narrow 
purpose: enable Secure Boot as defined by UEFI.

And from what I understand of their arguments so far, there is one and only 
one security concern: when in Secure Boot mode, a system must not allow 
execution of unsigned code with kernel privileges. So even if one can 
specify a different root filesystem and do a lot of nasty things to the 
system with a rogue userspace in that root filesystem, as long as the kernel 
won't load unsigned modules that's not a problem as far as they're 
concerned.

Also, AFAIK attacks requiring "physical presence" are out of scope for the 
UEFI Secure Boot security model. Thus an attack that involves control of a 
console of plugging an USB device is also not a concern.

One thing I don't know is whether an attack involving a networked IPMI 
console or a USB device that can be "plugged" virtually by a managing system 
(BMC) is considered a physical attack or a remote attack in the context of 
UEFI Secure Boot.

-- 
[]'s
Thiago Jung Bauermann
IBM Linux Technology Center

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Thread

[RFC 0/3] extend kexec_file_load system call AKASHI Takahiro <takahiro.akashi@linaro.org> - 2016-07-12 03:40 +0200
  Re: [RFC 0/3] extend kexec_file_load system call ebiederm@xmission.com (Eric W. Biederman) - 2016-07-12 15:40 +0200
    Re: [RFC 0/3] extend kexec_file_load system call Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> - 2016-07-12 16:00 +0200
      Re: [RFC 0/3] extend kexec_file_load system call Vivek Goyal <vgoyal@redhat.com> - 2016-07-12 16:10 +0200
        Re: [RFC 0/3] extend kexec_file_load system call Stewart Smith <stewart@linux.vnet.ibm.com> - 2016-07-13 01:50 +0200
          Re: [RFC 0/3] extend kexec_file_load system call Vivek Goyal <vgoyal@redhat.com> - 2016-07-13 15:30 +0200
    Re: [RFC 0/3] extend kexec_file_load system call Arnd Bergmann <arnd@arndb.de> - 2016-07-12 16:10 +0200
      Re: [RFC 0/3] extend kexec_file_load system call Vivek Goyal <vgoyal@redhat.com> - 2016-07-12 16:20 +0200
        Re: [RFC 0/3] extend kexec_file_load system call Arnd Bergmann <arnd@arndb.de> - 2016-07-12 16:30 +0200
          Re: [RFC 0/3] extend kexec_file_load system call Mark Rutland <mark.rutland@arm.com> - 2016-07-12 17:00 +0200
            Re: [RFC 0/3] extend kexec_file_load system call Dave Young <dyoung@redhat.com> - 2016-07-13 04:40 +0200
              Re: [RFC 0/3] extend kexec_file_load system call Arnd Bergmann <arnd@arndb.de> - 2016-07-13 10:10 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Stewart Smith <stewart@linux.vnet.ibm.com> - 2016-07-13 10:30 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Mark Rutland <mark.rutland@arm.com> - 2016-07-13 11:50 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Arnd Bergmann <arnd@arndb.de> - 2016-07-13 15:20 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> - 2016-07-13 20:50 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Arnd Bergmann <arnd@arndb.de> - 2016-07-13 22:10 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> - 2016-07-14 04:20 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Arnd Bergmann <arnd@arndb.de> - 2016-07-14 10:40 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> - 2016-07-15 03:50 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Arnd Bergmann <arnd@arndb.de> - 2016-07-15 09:40 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Vivek Goyal <vgoyal@redhat.com> - 2016-07-15 15:30 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Mark Rutland <mark.rutland@arm.com> - 2016-07-15 15:40 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> - 2016-07-15 17:30 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Mark Rutland <mark.rutland@arm.com> - 2016-07-15 17:50 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-07-15 15:50 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Arnd Bergmann <arnd@arndb.de> - 2016-07-15 22:30 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> - 2016-07-15 23:10 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> - 2016-07-22 02:20 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Jeremy Kerr <jeremy.kerr@au1.ibm.com> - 2016-07-22 03:00 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Michael Ellerman <michael@ellerman.id.au> - 2016-07-22 05:00 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> - 2016-07-22 22:50 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-07-15 10:50 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Vivek Goyal <vgoyal@redhat.com> - 2016-07-15 15:10 +0200
              Re: [RFC 0/3] extend kexec_file_load system call Mark Rutland <mark.rutland@arm.com> - 2016-07-13 11:40 +0200
                Re: [RFC 0/3] extend kexec_file_load system call AKASHI Takahiro <takahiro.akashi@linaro.org> - 2016-07-13 19:40 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Mark Rutland <mark.rutland@arm.com> - 2016-07-13 20:10 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Arnd Bergmann <arnd@arndb.de> - 2016-07-13 22:00 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Mark Rutland <mark.rutland@arm.com> - 2016-07-14 14:50 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Dave Young <dyoung@redhat.com> - 2016-07-14 04:00 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Dave Young <dyoung@redhat.com> - 2016-07-14 04:00 +0200
    Re: [RFC 0/3] extend kexec_file_load system call Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> - 2016-07-12 18:30 +0200
      Re: [RFC 0/3] extend kexec_file_load system call Petr Tesarik <ptesarik@suse.cz> - 2016-07-12 23:00 +0200
        Re: [RFC 0/3] extend kexec_file_load system call ebiederm@xmission.com (Eric W. Biederman) - 2016-07-12 23:40 +0200
          Re: [RFC 0/3] extend kexec_file_load system call ebiederm@xmission.com (Eric W. Biederman) - 2016-07-13 00:00 +0200
          Re: [RFC 0/3] extend kexec_file_load system call Petr Tesarik <ptesarik@suse.cz> - 2016-07-13 00:00 +0200
        Re: [RFC 0/3] extend kexec_file_load system call Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-07-13 00:20 +0200
          Re: [RFC 0/3] extend kexec_file_load system call Stewart Smith <stewart@linux.vnet.ibm.com> - 2016-07-13 07:10 +0200
            Re: [RFC 0/3] extend kexec_file_load system call Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-07-13 09:40 +0200
              Re: [RFC 0/3] extend kexec_file_load system call Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-07-13 09:50 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-07-13 10:20 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Stewart Smith <stewart@linux.vnet.ibm.com> - 2016-07-13 10:30 +0200
              Re: [RFC 0/3] extend kexec_file_load system call Stewart Smith <stewart@linux.vnet.ibm.com> - 2016-07-13 10:00 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-07-13 10:30 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Dave Young <dyoung@redhat.com> - 2016-07-13 10:40 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Petr Tesarik <ptesarik@suse.cz> - 2016-07-13 11:00 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Vivek Goyal <vgoyal@redhat.com> - 2016-07-13 15:10 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-07-13 19:50 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Vivek Goyal <vgoyal@redhat.com> - 2016-07-13 20:30 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Balbir Singh <bsingharora@gmail.com> - 2016-07-18 14:50 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Vivek Goyal <vgoyal@redhat.com> - 2016-07-18 15:30 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Vivek Goyal <vgoyal@redhat.com> - 2016-07-18 15:40 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Balbir Singh <bsingharora@gmail.com> - 2016-07-20 05:50 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-07-20 10:40 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Arnd Bergmann <arnd@arndb.de> - 2016-07-20 13:20 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> - 2016-07-20 18:00 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Vivek Goyal <vgoyal@redhat.com> - 2016-07-20 14:50 +0200
                Re: [RFC 0/3] extend kexec_file_load system call Vivek Goyal <vgoyal@redhat.com> - 2016-07-20 14:30 +0200
        Re: [RFC 0/3] extend kexec_file_load system call Stewart Smith <stewart@linux.vnet.ibm.com> - 2016-07-13 01:50 +0200
          Re: [RFC 0/3] extend kexec_file_load system call Vivek Goyal <vgoyal@redhat.com> - 2016-07-13 15:30 +0200

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