x86: Lock down IO port access when the kernel is locked down

IO port access would permit users to gain access to PCI configuration
registers, which in turn (on a lot of hardware) give access to MMIO
register space. This would potentially permit root to trigger arbitrary
DMA, so lock it down by default.

This also implicitly locks down the KDADDIO, KDDELIO, KDENABIO and
KDDISABIO console ioctls.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
cc: x86@kernel.org

Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0012-x86-Lock-down-IO-port-access-when-the-kernel-is-lock.patch

diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 2f723301eb58fc5ad0d6796b342446ae2ee0c9e6..b3758cc23262778d9299f3c58e2f052c0c172262 100644 (file)
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -31,7 +31,8 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
 
        if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
                return -EINVAL;
-       if (turn_on && !capable(CAP_SYS_RAWIO))
+       if (turn_on && (!capable(CAP_SYS_RAWIO) ||
+                       kernel_is_locked_down("ioperm")))
                return -EPERM;
 
        /*
@@ -121,7 +122,8 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
                return -EINVAL;
        /* Trying to gain more privileges? */
        if (level > old) {
-               if (!capable(CAP_SYS_RAWIO))
+               if (!capable(CAP_SYS_RAWIO) ||
+                   kernel_is_locked_down("iopl"))
                        return -EPERM;
        }
        regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |