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SubjectRe: [PATCH 11/27] x86: Lock down IO port access when the kernel is locked down
On Thu, Oct 19, 2017 at 03:51:56PM +0100, David Howells wrote:
> From: Matthew Garrett <matthew.garrett@nebula.com>
>
> 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>

I have reviewed this patch. Please feel free to add:

Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>

Thanks!
Joey Lee

> cc: x86@kernel.org
> ---
>
> arch/x86/kernel/ioport.c | 6 ++++--
> drivers/char/mem.c | 2 ++
> 2 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
> index 9c3cf0944bce..2c0f058651c5 100644
> --- a/arch/x86/kernel/ioport.c
> +++ b/arch/x86/kernel/ioport.c
> @@ -30,7 +30,8 @@ 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;
>
> /*
> @@ -120,7 +121,8 @@ 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) |
> diff --git a/drivers/char/mem.c b/drivers/char/mem.c
> index b7c36898b689..0875b3d47773 100644
> --- a/drivers/char/mem.c
> +++ b/drivers/char/mem.c
> @@ -768,6 +768,8 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
>
> static int open_port(struct inode *inode, struct file *filp)
> {
> + if (kernel_is_locked_down("Direct ioport access"))
> + return -EPERM;
> return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
> }
>
>
> --
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