From: Corey Minyard <minyard-HInyCGIudOg@public.gmane.org>
To: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
One Thousand Gnomes
<gnomes-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org>
Cc: keyrings-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
matthew.garrett-05XSO3Yj/JvQT0dZR+AlfA@public.gmane.org,
linux-security-module-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH] Lock down drivers that can have io ports, io mem, irqs and dma changed
Date: Mon, 28 Nov 2016 16:32:19 -0600 [thread overview]
Message-ID: <a4642e43-4598-96ca-c25a-2bd844631a47@acm.org> (raw)
In-Reply-To: <26173.1479769852-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
On 11/21/2016 05:10 PM, David Howells wrote:
> One Thousand Gnomes <gnomes-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org> wrote:
>
>> You need to filter or lock down kernel module options because a lot of
>> modules let you set the I/O port or similar (eg mmio) which means you can
>> hack the entire machine with say the 8250 driver just by using it with an
>> mmio of the right location to patch the secure state to zero just by
>> getting the ability to write to the modules conf file.
> Is the attached patch the right sort of idea? [Note that I haven't actually
> compiled most of these drivers to check my changes yet.]
>
> David
> ---
snip
> diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
> index a112c0146012..7fb9c299a183 100644
> --- a/drivers/char/ipmi/ipmi_si_intf.c
> +++ b/drivers/char/ipmi/ipmi_si_intf.c
> @@ -3725,6 +3725,12 @@ static int init_ipmi_si(void)
> struct smi_info *e;
> enum ipmi_addr_src type = SI_INVALID;
>
> + if ((num_addrs || num_ports || num_irqs) &&
> + kernel_is_locked_down()) {
> + pr_err(PFX "Kernel is locked down\n");
> + return -EPERM;
> + }
> +
> if (initialized)
> return 0;
> initialized = 1;
This would prevent any IPMI interface from working if any address was given
on the kernel command line. I'm not sure what the best policy is, but that
sounds like a possible DOS to me.
Can you put this check in hardcode_find_bmc()? Thats the only place where
the hardcoded addresses are used, and a check there won't affect anything
else.
Also, the error message sounds a little vague to me. If I was a sysadmin
and got this, I wouldn't be sure what was going on. Maybe something like:
The kernel is locked down, but hard-coded device addresses were given on
the driver command line. Ignoring these, but this is a possible
security issue.
That's fairly wordy, but it gets the point across. You could also move the
pr_err() into kernel_is_locked_down() and pass in the prefix, since there is
basically the same pr_err() after every check.
Thanks,
-corey
next prev parent reply other threads:[~2016-11-28 22:32 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-16 21:47 [PATCH 00/16] Kernel lockdown David Howells
2016-11-16 21:47 ` [PATCH 01/16] Add the ability to lock down access to the running kernel image David Howells
[not found] ` <147933284407.19316.17886320817060158597.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2016-11-16 22:20 ` Borislav Petkov
2016-11-16 22:40 ` David Howells
2016-12-25 21:20 ` Pavel Machek
2016-12-25 21:44 ` David Howells
2016-11-16 21:47 ` [PATCH 02/16] efi: Get the secure boot status David Howells
2016-11-17 12:37 ` Lukas Wunner
2016-11-22 0:31 ` [PATCH 2/6] arm/efi: Allow invocation of arbitrary runtime services David Howells
2016-11-22 0:31 ` [PATCH 3/6] efi: Add SHIM and image security database GUID definitions David Howells
2016-11-22 0:32 ` [PATCH 4/6] efi: Get the secure boot status David Howells
2016-11-22 10:44 ` Lukas Wunner
[not found] ` <20161122104401.GC1552-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>
2016-11-22 10:49 ` Ard Biesheuvel
2016-11-22 14:52 ` David Howells
[not found] ` <25371.1479826321-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2016-11-22 20:36 ` Lukas Wunner
2016-11-22 14:47 ` David Howells
2016-11-22 20:30 ` Lukas Wunner
2016-11-23 0:02 ` David Howells
[not found] ` <7199.1479826047-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2016-11-22 14:57 ` David Howells
2016-11-22 0:32 ` [PATCH 5/6] efi: Disable secure boot if shim is in insecure mode David Howells
2016-11-22 13:03 ` Lukas Wunner
2016-11-22 0:32 ` [PATCH 6/6] efi: Add EFI_SECURE_BOOT bit David Howells
2016-11-22 13:04 ` Lukas Wunner
2016-11-21 11:46 ` [PATCH 02/16] efi: Get the secure boot status David Howells
2016-11-21 19:58 ` Lukas Wunner
[not found] ` <20161117123731.GA11573-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>
2016-11-21 11:42 ` David Howells
[not found] ` <29779.1479728545-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2016-11-21 11:52 ` Ard Biesheuvel
[not found] ` <CAKv+Gu-frVDhzORDRZ6XT+FxewsTgrxhXmM=DqaS6Ns4mJhQ9g-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-11-21 12:41 ` David Howells
2016-11-21 13:14 ` Ard Biesheuvel
[not found] ` <CAKv+Gu8Lhm=u97hY1y+Y+Ladk=y7pSVNrow8ML1hQUJ9+74B-w-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-11-21 15:17 ` Lukas Wunner
2016-11-21 15:25 ` Ard Biesheuvel
2016-11-22 0:31 ` [PATCH 1/6] x86/efi: Allow invocation of arbitrary runtime services David Howells
[not found] ` <147977469914.6360.17194649697208113702.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2016-11-22 10:20 ` Lukas Wunner
2016-11-22 14:17 ` David Howells
2016-11-22 14:58 ` Joe Perches
[not found] ` <1479826691.1942.11.camel-6d6DIl74uiNBDgjK7y7TUQ@public.gmane.org>
2016-11-22 15:52 ` David Howells
[not found] ` <24973.1479829961-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2016-11-22 16:25 ` Joe Perches
2016-11-22 16:40 ` David Howells
2016-11-22 16:51 ` Joe Perches
2016-11-16 21:47 ` [PATCH 03/16] efi: Disable secure boot if shim is in insecure mode David Howells
2016-11-16 21:47 ` [PATCH 04/16] efi: Lock down the kernel if booted in secure boot mode David Howells
2016-11-16 21:47 ` [PATCH 05/16] efi: Add EFI_SECURE_BOOT bit David Howells
2016-11-17 21:58 ` Ard Biesheuvel
2016-11-18 11:58 ` Josh Boyer
[not found] ` <CA+5PVA6F5qEnuL2UaXS9_fJ217J93cEZDDsz9Y2BPwHXcMdX-A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-11-18 12:10 ` Ard Biesheuvel
[not found] ` <CAKv+Gu_8r3oM-jvvuSiXTzxp0YMEVgc5KkScJ2UhGTaXm28L6w-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-11-18 17:28 ` David Howells
2016-11-16 21:48 ` [PATCH 06/16] Add a sysrq option to exit secure boot mode David Howells
2016-11-16 21:48 ` [PATCH 07/16] kexec: Disable at runtime if the kernel is locked down David Howells
2016-11-16 21:48 ` [PATCH 08/16] Copy secure_boot flag in boot params across kexec reboot David Howells
2016-11-16 21:48 ` [PATCH 09/16] hibernate: Disable when the kernel is locked down David Howells
2016-11-16 21:48 ` [PATCH 10/16] PCI: Lock down BAR access " David Howells
[not found] ` <147933283664.19316.12454053022687659937.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2016-11-16 21:48 ` [PATCH 11/16] x86: Lock down IO port " David Howells
2016-11-16 21:49 ` [PATCH 16/16] x86: Restrict MSR " David Howells
2016-11-16 22:27 ` [PATCH 00/16] Kernel lockdown One Thousand Gnomes
2016-11-21 19:53 ` Ard Biesheuvel
2016-11-30 14:27 ` One Thousand Gnomes
2016-11-16 21:48 ` [PATCH 12/16] ACPI: Limit access to custom_method when the kernel is locked down David Howells
2016-11-16 21:48 ` [PATCH 13/16] asus-wmi: Restrict debugfs interface " David Howells
2016-11-16 21:48 ` [PATCH 14/16] Restrict /dev/mem and /dev/kmem " David Howells
2016-11-16 21:49 ` [PATCH 15/16] acpi: Ignore acpi_rsdp kernel param when the kernel has been " David Howells
2016-11-16 22:28 ` [PATCH 00/16] Kernel lockdown Justin Forbes
2016-11-21 23:10 ` [PATCH] Lock down drivers that can have io ports, io mem, irqs and dma changed David Howells
2016-11-22 6:12 ` Dominik Brodowski
2016-11-23 12:58 ` David Howells
2016-11-23 19:21 ` Dominik Brodowski
[not found] ` <20161123192143.GA482-SGhQLRGLuNwb6pqDj42GsMgv3T4z79SOrE5yTffgRl4@public.gmane.org>
2016-11-24 17:34 ` David Howells
2016-11-24 20:19 ` Dominik Brodowski
2016-11-25 14:49 ` David Howells
[not found] ` <26173.1479769852-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2016-11-28 22:32 ` Corey Minyard [this message]
2016-11-29 0:11 ` David Howells
2016-11-29 0:23 ` Corey Minyard
2016-11-29 14:03 ` David Howells
[not found] ` <6973.1480428211-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2016-11-29 14:35 ` Corey Minyard
2016-11-30 14:41 ` One Thousand Gnomes
[not found] ` <20161130144105.2b6be4fe-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org>
2016-11-30 16:25 ` David Howells
2016-11-29 10:40 ` David Howells
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