From: Kees Cook <keescook@xxxxxxxxxxxx> Writing to MSRs should not be allowed unless CAP_COMPROMISE_KERNEL is set since it could lead to execution of arbitrary code in kernel mode. Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Signed-off-by: Matthew Garrett <matthew.garrett@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 ce13049..fa4dc6c 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -103,6 +103,9 @@ static ssize_t msr_write(struct file *file, const char __user *buf, int err = 0; ssize_t bytes = 0; + if (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + if (count % 8) return -EINVAL; /* Invalid chunk size */ @@ -150,6 +153,10 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg) err = -EBADF; break; } + if (!capable(CAP_COMPROMISE_KERNEL)) { + err = -EPERM; + break; + } if (copy_from_user(®s, uregs, sizeof regs)) { err = -EFAULT; break; -- 1.8.1.2 -- 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