From: Kees Cook <keescook@chromium.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Matthew Garrett <matthew.garrett@nebula.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
x86@kernel.org, linux-efi@vger.kernel.org,
linux-security-module <linux-security-module@vger.kernel.org>
Subject: Re: [PATCH] x86: Lock down MSR writing in secure boot
Date: Fri, 8 Feb 2013 11:18:54 -0800 [thread overview]
Message-ID: <CAGXu5jJnLY6Qp3J6HBpVg-AdUGdKYm-e4wErZO3=NuRo04ajvg@mail.gmail.com> (raw)
In-Reply-To: <00780235-deac-4f80-b936-867834e05661@email.android.com>
No. CAP_RAWIO is for reading. Writing needs a much stronger check.
-Kees
On Fri, Feb 8, 2013 at 11:17 AM, H. Peter Anvin <hpa@zytor.com> wrote:
> We already have CAP_RAWIO for this in mainline; I am not sure if this should be harder than that...
>
> Kees Cook <keescook@chromium.org> wrote:
>
>>Writing to MSRs should not be allowed unless CAP_COMPROMISE_KERNEL is
>>set since it could lead to execution of arbitrary code in kernel mode.
>>
>>Signed-off-by: Kees Cook <keescook@chromium.org>
>>---
>>This would be used on top of Matthew Garrett's existing "Secure boot
>>policy support" patch series.
>>---
>> arch/x86/kernel/msr.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>>diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
>>index 4929502..adaab3d 100644
>>--- a/arch/x86/kernel/msr.c
>>+++ b/arch/x86/kernel/msr.c
>>@@ -103,6 +103,9 @@ static ssize_t msr_write(struct file *file, const
>>char __user *buf,
>> int err = 0;
>> ssize_t bytes = 0;
>>
>>+ if (!capable(CAP_COMPROMISE_KERNEL))
>>+ return -EPERM;
>>+
>> if (count % 8)
>> return -EINVAL; /* Invalid chunk size */
>>
>>@@ -150,6 +153,10 @@ static long msr_ioctl(struct file *file, unsigned
>>int ioc, unsigned long arg)
>> err = -EBADF;
>> break;
>> }
>>+ if (!capable(CAP_COMPROMISE_KERNEL)) {
>>+ err = -EPERM;
>>+ break;
>>+ }
>> if (copy_from_user(®s, uregs, sizeof regs)) {
>> err = -EFAULT;
>> break;
>
> --
> Sent from my mobile phone. Please excuse brevity and lack of formatting.
--
Kees Cook
Chrome OS Security
next prev parent reply other threads:[~2013-02-08 19:18 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-08 19:12 [PATCH] x86: Lock down MSR writing in secure boot Kees Cook
2013-02-08 19:17 ` H. Peter Anvin
2013-02-08 19:18 ` Kees Cook [this message]
2013-02-08 19:42 ` H. Peter Anvin
2013-02-08 20:14 ` Kees Cook
2013-02-08 20:18 ` H. Peter Anvin
2013-02-08 20:28 ` Kees Cook
2013-02-08 20:34 ` Matthew Garrett
2013-02-08 21:02 ` Kees Cook
2013-02-08 21:07 ` Matthew Garrett
2013-02-08 21:14 ` Josh Boyer
2013-02-08 23:09 ` Andy Lutomirski
2013-02-08 22:30 ` H. Peter Anvin
2013-02-08 23:06 ` Borislav Petkov
2013-02-08 23:26 ` Matthew Garrett
2013-02-09 1:22 ` H. Peter Anvin
2013-02-09 1:29 ` Matthew Garrett
2013-02-09 6:45 ` Kees Cook
2013-02-09 9:29 ` Borislav Petkov
2013-02-09 15:10 ` Kees Cook
2013-02-09 15:11 ` Matthew Garrett
2013-02-13 0:48 ` H. Peter Anvin
2013-02-13 5:39 ` Matthew Garrett
2013-02-13 6:12 ` H. Peter Anvin
2013-02-13 6:27 ` Matthew Garrett
2013-02-13 6:33 ` H. Peter Anvin
2013-02-13 6:41 ` Matthew Garrett
2013-02-13 17:20 ` H. Peter Anvin
2013-02-13 17:26 ` Matthew Garrett
2013-02-13 17:51 ` Casey Schaufler
2013-02-13 17:56 ` Matthew Garrett
2013-02-13 18:44 ` H. Peter Anvin
2013-02-13 18:51 ` Matthew Garrett
2013-02-13 22:26 ` H. Peter Anvin
2013-02-13 22:58 ` Casey Schaufler
2013-02-14 0:25 ` H. Peter Anvin
2013-02-14 0:44 ` Casey Schaufler
2013-02-14 1:04 ` Matthew Garrett
2013-02-14 1:08 ` H. Peter Anvin
2013-02-14 2:46 ` Matthew Garrett
2013-02-14 1:34 ` Casey Schaufler
2013-02-13 8:27 ` Paolo Bonzini
2013-02-13 17:21 ` H. Peter Anvin
2013-02-13 17:22 ` H. Peter Anvin
2013-02-13 19:55 ` Paolo Bonzini
2013-02-13 22:24 ` H. Peter Anvin
2013-02-08 19:17 ` Matthew Garrett
2013-02-08 19:21 ` Kees Cook
2013-02-08 19:27 ` Matthew Garrett
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