From: Matthew Garrett Date: Wed, 8 Nov 2017 15:11:34 +0000 Subject: [12/29] x86: Lock down IO port access when the kernel is locked down Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=00ebba940247d4c37c06da4aedecf6b80db213cf 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 Signed-off-by: David Howells Reviewed-by: Thomas Gleixner Reviewed-by: "Lee, Chun-Yi" cc: x86@kernel.org --- arch/x86/kernel/ioport.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) Index: linux/arch/x86/kernel/ioport.c =================================================================== --- linux.orig/arch/x86/kernel/ioport.c +++ linux/arch/x86/kernel/ioport.c @@ -31,7 +31,8 @@ long ksys_ioperm(unsigned long from, uns 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; /* @@ -126,7 +127,8 @@ SYSCALL_DEFINE1(iopl, unsigned int, leve 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) |