On Thu, Oct 19, 2017 at 03:52:04PM +0100, David Howells wrote: > From: Matthew Garrett <matthew.garrett@xxxxxxxxxx> > > 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 <matthew.garrett@xxxxxxxxxx> > Signed-off-by: David Howells <dhowells@xxxxxxxxxx> > Acked-by: Kees Cook <keescook@xxxxxxxxxxxx> > Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> I have reviewed this patch. Please feel free to add: Reviewed-by: "Lee, Chun-Yi" <jlee@xxxxxxxx> Thanks! Joey Lee > cc: x86@xxxxxxxxxx > --- > > 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 ef688804f80d..a05a97863286 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")) > + return -EPERM; > + > if (count % 8) > return -EINVAL; /* Invalid chunk size */ > > @@ -131,6 +134,10 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg) > err = -EBADF; > break; > } > + if (kernel_is_locked_down("Direct MSR access")) { > + err = -EPERM; > + break; > + } > if (copy_from_user(®s, uregs, sizeof regs)) { > err = -EFAULT; > break; > > -- > To unsubscribe from this list: send the line "unsubscribe linux-efi" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html