Messages in this thread Patch in this message | | | Date | Tue, 26 Mar 2019 11:27:28 -0700 | Subject | [PATCH V31 12/25] x86/msr: Restrict MSR access when the kernel is locked down | From | Matthew Garrett <> |
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From: Matthew Garrett <mjg59@srcf.ucam.org>
Writing to MSRs should not be allowed if the kernel is locked down, since it could lead to execution of arbitrary code in kernel mode. Based on a patch by Kees Cook.
Signed-off-by: Matthew Garrett <mjg59@google.com> Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Kees Cook <keescook@chromium.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> cc: x86@kernel.org --- arch/x86/kernel/msr.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c index 4588414e2561..731be1be52b6 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -84,6 +84,9 @@ 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", LOCKDOWN_INTEGRITY)) + return -EPERM; + if (count % 8) return -EINVAL; /* Invalid chunk size */ @@ -135,6 +138,11 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg) err = -EFAULT; break; } + if (kernel_is_locked_down("Direct MSR access", + LOCKDOWN_INTEGRITY)) { + err = -EPERM; + break; + } err = wrmsr_safe_regs_on_cpu(cpu, regs); if (err) break; -- 2.21.0.392.gf8f6787159e-goog
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