47 lines
1.2 KiB
Diff
47 lines
1.2 KiB
Diff
From: Matthew Garrett <mjg59@srcf.ucam.org>
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Date: Fri, 8 Feb 2013 11:12:13 -0800
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Subject: [10/18] x86: Restrict MSR access when securelevel is set
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Origin: https://github.com/mjg59/linux/commit/c6ad37822699967e60fae57a64ae89676f543182
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Permitting write access to MSRs allows userspace to modify the running
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kernel. Prevent this if securelevel has been set. Based on a patch by Kees
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Cook.
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Cc: Kees Cook <keescook@chromium.org>
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Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
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---
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arch/x86/kernel/msr.c | 8 ++++++++
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1 file changed, 8 insertions(+)
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--- a/arch/x86/kernel/msr.c
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+++ b/arch/x86/kernel/msr.c
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@@ -39,6 +39,7 @@
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#include <linux/notifier.h>
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#include <linux/uaccess.h>
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#include <linux/gfp.h>
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+#include <linux/security.h>
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#include <asm/cpufeature.h>
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#include <asm/msr.h>
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@@ -83,6 +84,9 @@ static ssize_t msr_write(struct file *fi
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int err = 0;
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ssize_t bytes = 0;
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+ if (get_securelevel() > 0)
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+ return -EPERM;
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+
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if (count % 8)
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return -EINVAL; /* Invalid chunk size */
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@@ -130,6 +134,10 @@ static long msr_ioctl(struct file *file,
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err = -EBADF;
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break;
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}
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+ if (get_securelevel() > 0) {
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+ err = -EPERM;
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+ break;
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+ }
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if (copy_from_user(®s, uregs, sizeof regs)) {
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err = -EFAULT;
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break;
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