42 lines
1.3 KiB
Diff
42 lines
1.3 KiB
Diff
From: Matthew Garrett <matthew.garrett@nebula.com>
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Date: Wed, 5 Apr 2017 17:40:30 +0100
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Subject: [52/62] x86: Restrict MSR access when the kernel is locked down
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Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=e20ab2be2f77e6c0da7cd8fe0953a367c5012ecf
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Writing to MSRs should not be allowed if the kernel is locked down, since
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it could lead to execution of arbitrary code in kernel mode. Based on a
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patch by Kees Cook.
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Cc: Kees Cook <keescook@chromium.org>
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Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
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Signed-off-by: David Howells <dhowells@redhat.com>
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---
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arch/x86/kernel/msr.c | 7 +++++++
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1 file changed, 7 insertions(+)
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diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
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index ef688804f80d..fbcce028e502 100644
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--- a/arch/x86/kernel/msr.c
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+++ b/arch/x86/kernel/msr.c
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@@ -84,6 +84,9 @@ static ssize_t msr_write(struct file *file, const char __user *buf,
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int err = 0;
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ssize_t bytes = 0;
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+ if (kernel_is_locked_down())
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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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@@ -131,6 +134,10 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
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err = -EBADF;
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break;
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}
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+ if (kernel_is_locked_down()) {
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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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