[PATCH 12/27] x86/msr: Restrict MSR access when the kernel is locked down
From: jlee@suse.com (joeyli)
Date: 2017-10-25 14:04:05
Also in:
linux-efi, lkml
Hi David, On Mon, Oct 23, 2017 at 03:49:44PM +0100, David Howells wrote:
Alan Cox [off-list ref] wrote:quoted
There are a load of standard tools that use this so I think you are going to need a whitelist. Can you at least log *which* MSR in the failing case so a whitelist can be built over time ?Will the attached change work for you?
It's good to me. Joey Lee
quoted hunk ↗ jump to hunk
---diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c index a05a97863286..f18cadbc31ce 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c@@ -84,8 +84,10 @@ static ssize_t msr_write(struct file *file, const char __user *buf, int err = 0; ssize_t bytes = 0; - if (kernel_is_locked_down("Direct MSR access")) + if (kernel_is_locked_down("Direct MSR access")) { + pr_info("Direct access to MSR %x\n", reg); return -EPERM; + } if (count % 8) return -EINVAL; /* Invalid chunk size */@@ -135,6 +137,7 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg) break; } if (kernel_is_locked_down("Direct MSR access")) { + pr_info("Direct access to MSR %x\n", reg[1]); /* Display %ecx */ err = -EPERM; break; }
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